// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      uvc_driver.c  --  USB Video Class driver
 *
 *      Copyright (C) 2005-2010
 *          Laurent Pinchart (laurent.pinchart@ideasonboard.com)
 */

#include <linux/atomic.h>
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/videodev2.h>
#include <linux/vmalloc.h>
#include <linux/wait.h>
#include <linux/version.h>
#include <asm/unaligned.h>

#include <media/v4l2-common.h>
#include <media/v4l2-ioctl.h>

#include "uvcvideo.h"

#define DRIVER_AUTHOR           "Laurent Pinchart " \
                                "<laurent.pinchart@ideasonboard.com>"
#define DRIVER_DESC             "USB Video Class driver"

unsigned int uvc_clock_param = CLOCK_MONOTONIC;
unsigned int uvc_hw_timestamps_param;
unsigned int uvc_no_drop_param;
static unsigned int uvc_quirks_param = -1;
unsigned int uvc_dbg_param;
unsigned int uvc_timeout_param = UVC_CTRL_STREAMING_TIMEOUT;

/* ------------------------------------------------------------------------
 * Video formats
 */

static struct uvc_format_desc uvc_fmts[] = {
        {
                .name           = "YUV 4:2:2 (YUYV)",
                .guid           = UVC_GUID_FORMAT_YUY2,
                .fcc            = V4L2_PIX_FMT_YUYV,
        },
        {
                .name           = "YUV 4:2:2 (YUYV)",
                .guid           = UVC_GUID_FORMAT_YUY2_ISIGHT,
                .fcc            = V4L2_PIX_FMT_YUYV,
        },
        {
                .name           = "YUV 4:2:0 (NV12)",
                .guid           = UVC_GUID_FORMAT_NV12,
                .fcc            = V4L2_PIX_FMT_NV12,
        },
        {
                .name           = "MJPEG",
                .guid           = UVC_GUID_FORMAT_MJPEG,
                .fcc            = V4L2_PIX_FMT_MJPEG,
        },
        {
                .name           = "YVU 4:2:0 (YV12)",
                .guid           = UVC_GUID_FORMAT_YV12,
                .fcc            = V4L2_PIX_FMT_YVU420,
        },
        {
                .name           = "YUV 4:2:0 (I420)",
                .guid           = UVC_GUID_FORMAT_I420,
                .fcc            = V4L2_PIX_FMT_YUV420,
        },
        {
                .name           = "YUV 4:2:0 (M420)",
                .guid           = UVC_GUID_FORMAT_M420,
                .fcc            = V4L2_PIX_FMT_M420,
        },
        {
                .name           = "YUV 4:2:2 (UYVY)",
                .guid           = UVC_GUID_FORMAT_UYVY,
                .fcc            = V4L2_PIX_FMT_UYVY,
        },
        {
                .name           = "Greyscale 8-bit (Y800)",
                .guid           = UVC_GUID_FORMAT_Y800,
                .fcc            = V4L2_PIX_FMT_GREY,
        },
        {
                .name           = "Greyscale 8-bit (Y8  )",
                .guid           = UVC_GUID_FORMAT_Y8,
                .fcc            = V4L2_PIX_FMT_GREY,
        },
        {
                .name           = "Greyscale 8-bit (D3DFMT_L8)",
                .guid           = UVC_GUID_FORMAT_D3DFMT_L8,
                .fcc            = V4L2_PIX_FMT_GREY,
        },
        {
                .name           = "IR 8-bit (L8_IR)",
                .guid           = UVC_GUID_FORMAT_KSMEDIA_L8_IR,
                .fcc            = V4L2_PIX_FMT_GREY,
        },
        {
                .name           = "Greyscale 10-bit (Y10 )",
                .guid           = UVC_GUID_FORMAT_Y10,
                .fcc            = V4L2_PIX_FMT_Y10,
        },
        {
                .name           = "Greyscale 12-bit (Y12 )",
                .guid           = UVC_GUID_FORMAT_Y12,
                .fcc            = V4L2_PIX_FMT_Y12,
        },
        {
                .name           = "Greyscale 16-bit (Y16 )",
                .guid           = UVC_GUID_FORMAT_Y16,
                .fcc            = V4L2_PIX_FMT_Y16,
        },
        {
                .name           = "BGGR Bayer (BY8 )",
                .guid           = UVC_GUID_FORMAT_BY8,
                .fcc            = V4L2_PIX_FMT_SBGGR8,
        },
        {
                .name           = "BGGR Bayer (BA81)",
                .guid           = UVC_GUID_FORMAT_BA81,
                .fcc            = V4L2_PIX_FMT_SBGGR8,
        },
        {
                .name           = "GBRG Bayer (GBRG)",
                .guid           = UVC_GUID_FORMAT_GBRG,
                .fcc            = V4L2_PIX_FMT_SGBRG8,
        },
        {
                .name           = "GRBG Bayer (GRBG)",
                .guid           = UVC_GUID_FORMAT_GRBG,
                .fcc            = V4L2_PIX_FMT_SGRBG8,
        },
        {
                .name           = "RGGB Bayer (RGGB)",
                .guid           = UVC_GUID_FORMAT_RGGB,
                .fcc            = V4L2_PIX_FMT_SRGGB8,
        },
        {
                .name           = "RGB565",
                .guid           = UVC_GUID_FORMAT_RGBP,
                .fcc            = V4L2_PIX_FMT_RGB565,
        },
        {
                .name           = "BGR 8:8:8 (BGR3)",
                .guid           = UVC_GUID_FORMAT_BGR3,
                .fcc            = V4L2_PIX_FMT_BGR24,
        },
        {
                .name           = "H.264",
                .guid           = UVC_GUID_FORMAT_H264,
                .fcc            = V4L2_PIX_FMT_H264,
        },
        {
                .name           = "Greyscale 8 L/R (Y8I)",
                .guid           = UVC_GUID_FORMAT_Y8I,
                .fcc            = V4L2_PIX_FMT_Y8I,
        },
        {
                .name           = "Greyscale 12 L/R (Y12I)",
                .guid           = UVC_GUID_FORMAT_Y12I,
                .fcc            = V4L2_PIX_FMT_Y12I,
        },
        {
                .name           = "Depth data 16-bit (Z16)",
                .guid           = UVC_GUID_FORMAT_Z16,
                .fcc            = V4L2_PIX_FMT_Z16,
        },
        {
                .name           = "Bayer 10-bit (SRGGB10P)",
                .guid           = UVC_GUID_FORMAT_RW10,
                .fcc            = V4L2_PIX_FMT_SRGGB10P,
        },
        {
                .name           = "Bayer 16-bit (SBGGR16)",
                .guid           = UVC_GUID_FORMAT_BG16,
                .fcc            = V4L2_PIX_FMT_SBGGR16,
        },
        {
                .name           = "Bayer 16-bit (SGBRG16)",
                .guid           = UVC_GUID_FORMAT_GB16,
                .fcc            = V4L2_PIX_FMT_SGBRG16,
        },
        {
                .name           = "Bayer 16-bit (SRGGB16)",
                .guid           = UVC_GUID_FORMAT_RG16,
                .fcc            = V4L2_PIX_FMT_SRGGB16,
        },
        {
                .name           = "Bayer 16-bit (SGRBG16)",
                .guid           = UVC_GUID_FORMAT_GR16,
                .fcc            = V4L2_PIX_FMT_SGRBG16,
        },
        {
                .name           = "Depth data 16-bit (Z16)",
                .guid           = UVC_GUID_FORMAT_INVZ,
                .fcc            = V4L2_PIX_FMT_Z16,
        },
        {
                .name           = "Greyscale 10-bit (Y10 )",
                .guid           = UVC_GUID_FORMAT_INVI,
                .fcc            = V4L2_PIX_FMT_Y10,
        },
        {
                .name           = "IR:Depth 26-bit (INZI)",
                .guid           = UVC_GUID_FORMAT_INZI,
                .fcc            = V4L2_PIX_FMT_INZI,
        },
        {
                .name           = "4-bit Depth Confidence (Packed)",
                .guid           = UVC_GUID_FORMAT_CNF4,
                .fcc            = V4L2_PIX_FMT_CNF4,
        },
        {
                .name           = "HEVC",
                .guid           = UVC_GUID_FORMAT_HEVC,
                .fcc            = V4L2_PIX_FMT_HEVC,
        },
};

/* ------------------------------------------------------------------------
 * Utility functions
 */

struct usb_host_endpoint *uvc_find_endpoint(struct usb_host_interface *alts,
                u8 epaddr)
{
        struct usb_host_endpoint *ep;
        unsigned int i;

        for (i = 0; i < alts->desc.bNumEndpoints; ++i) {
                ep = &alts->endpoint[i];
                if (ep->desc.bEndpointAddress == epaddr)
                        return ep;
        }

        return NULL;
}

static struct uvc_format_desc *uvc_format_by_guid(const u8 guid[16])
{
        unsigned int len = ARRAY_SIZE(uvc_fmts);
        unsigned int i;

        for (i = 0; i < len; ++i) {
                if (memcmp(guid, uvc_fmts[i].guid, 16) == 0)
                        return &uvc_fmts[i];
        }

        return NULL;
}

static enum v4l2_colorspace uvc_colorspace(const u8 primaries)
{
        static const enum v4l2_colorspace colorprimaries[] = {
                V4L2_COLORSPACE_DEFAULT,  /* Unspecified */
                V4L2_COLORSPACE_SRGB,
                V4L2_COLORSPACE_470_SYSTEM_M,
                V4L2_COLORSPACE_470_SYSTEM_BG,
                V4L2_COLORSPACE_SMPTE170M,
                V4L2_COLORSPACE_SMPTE240M,
        };

        if (primaries < ARRAY_SIZE(colorprimaries))
                return colorprimaries[primaries];

        return V4L2_COLORSPACE_DEFAULT;  /* Reserved */
}

static enum v4l2_xfer_func uvc_xfer_func(const u8 transfer_characteristics)
{
        /*
         * V4L2 does not currently have definitions for all possible values of
         * UVC transfer characteristics. If v4l2_xfer_func is extended with new
         * values, the mapping below should be updated.
         *
         * Substitutions are taken from the mapping given for
         * V4L2_XFER_FUNC_DEFAULT documented in videodev2.h.
         */
        static const enum v4l2_xfer_func xfer_funcs[] = {
                V4L2_XFER_FUNC_DEFAULT,    /* Unspecified */
                V4L2_XFER_FUNC_709,
                V4L2_XFER_FUNC_709,        /* Substitution for BT.470-2 M */
                V4L2_XFER_FUNC_709,        /* Substitution for BT.470-2 B, G */
                V4L2_XFER_FUNC_709,        /* Substitution for SMPTE 170M */
                V4L2_XFER_FUNC_SMPTE240M,
                V4L2_XFER_FUNC_NONE,
                V4L2_XFER_FUNC_SRGB,
        };

        if (transfer_characteristics < ARRAY_SIZE(xfer_funcs))
                return xfer_funcs[transfer_characteristics];

        return V4L2_XFER_FUNC_DEFAULT;  /* Reserved */
}

static enum v4l2_ycbcr_encoding uvc_ycbcr_enc(const u8 matrix_coefficients)
{
        /*
         * V4L2 does not currently have definitions for all possible values of
         * UVC matrix coefficients. If v4l2_ycbcr_encoding is extended with new
         * values, the mapping below should be updated.
         *
         * Substitutions are taken from the mapping given for
         * V4L2_YCBCR_ENC_DEFAULT documented in videodev2.h.
         *
         * FCC is assumed to be close enough to 601.
         */
        static const enum v4l2_ycbcr_encoding ycbcr_encs[] = {
                V4L2_YCBCR_ENC_DEFAULT,  /* Unspecified */
                V4L2_YCBCR_ENC_709,
                V4L2_YCBCR_ENC_601,      /* Substitution for FCC */
                V4L2_YCBCR_ENC_601,      /* Substitution for BT.470-2 B, G */
                V4L2_YCBCR_ENC_601,
                V4L2_YCBCR_ENC_SMPTE240M,
        };

        if (matrix_coefficients < ARRAY_SIZE(ycbcr_encs))
                return ycbcr_encs[matrix_coefficients];

        return V4L2_YCBCR_ENC_DEFAULT;  /* Reserved */
}

/* Simplify a fraction using a simple continued fraction decomposition. The
 * idea here is to convert fractions such as 333333/10000000 to 1/30 using
 * 32 bit arithmetic only. The algorithm is not perfect and relies upon two
 * arbitrary parameters to remove non-significative terms from the simple
 * continued fraction decomposition. Using 8 and 333 for n_terms and threshold
 * respectively seems to give nice results.
 */
void uvc_simplify_fraction(u32 *numerator, u32 *denominator,
                unsigned int n_terms, unsigned int threshold)
{
        u32 *an;
        u32 x, y, r;
        unsigned int i, n;

        an = kmalloc_array(n_terms, sizeof(*an), GFP_KERNEL);
        if (an == NULL)
                return;

        /* Convert the fraction to a simple continued fraction. See
         * https://mathforum.org/dr.math/faq/faq.fractions.html
         * Stop if the current term is bigger than or equal to the given
         * threshold.
         */
        x = *numerator;
        y = *denominator;

        for (n = 0; n < n_terms && y != 0; ++n) {
                an[n] = x / y;
                if (an[n] >= threshold) {
                        if (n < 2)
                                n++;
                        break;
                }

                r = x - an[n] * y;
                x = y;
                y = r;
        }

        /* Expand the simple continued fraction back to an integer fraction. */
        x = 0;
        y = 1;

        for (i = n; i > 0; --i) {
                r = y;
                y = an[i-1] * y + x;
                x = r;
        }

        *numerator = y;
        *denominator = x;
        kfree(an);
}

/* Convert a fraction to a frame interval in 100ns multiples. The idea here is
 * to compute numerator / denominator * 10000000 using 32 bit fixed point
 * arithmetic only.
 */
u32 uvc_fraction_to_interval(u32 numerator, u32 denominator)
{
        u32 multiplier;

        /* Saturate the result if the operation would overflow. */
        if (denominator == 0 ||
            numerator/denominator >= ((u32)-1)/10000000)
                return (u32)-1;

        /* Divide both the denominator and the multiplier by two until
         * numerator * multiplier doesn't overflow. If anyone knows a better
         * algorithm please let me know.
         */
        multiplier = 10000000;
        while (numerator > ((u32)-1)/multiplier) {
                multiplier /= 2;
                denominator /= 2;
        }

        return denominator ? numerator * multiplier / denominator : 0;
}

/* ------------------------------------------------------------------------
 * Terminal and unit management
 */

struct uvc_entity *uvc_entity_by_id(struct uvc_device *dev, int id)
{
        struct uvc_entity *entity;

        list_for_each_entry(entity, &dev->entities, list) {
                if (entity->id == id)
                        return entity;
        }

        return NULL;
}

static struct uvc_entity *uvc_entity_by_reference(struct uvc_device *dev,
        int id, struct uvc_entity *entity)
{
        unsigned int i;

        if (entity == NULL)
                entity = list_entry(&dev->entities, struct uvc_entity, list);

        list_for_each_entry_continue(entity, &dev->entities, list) {
                for (i = 0; i < entity->bNrInPins; ++i)
                        if (entity->baSourceID[i] == id)
                                return entity;
        }

        return NULL;
}

static struct uvc_streaming *uvc_stream_by_id(struct uvc_device *dev, int id)
{
        struct uvc_streaming *stream;

        list_for_each_entry(stream, &dev->streams, list) {
                if (stream->header.bTerminalLink == id)
                        return stream;
        }

        return NULL;
}

/* ------------------------------------------------------------------------
 * Streaming Object Management
 */

static void uvc_stream_delete(struct uvc_streaming *stream)
{
        if (stream->async_wq)
                destroy_workqueue(stream->async_wq);

        mutex_destroy(&stream->mutex);

        usb_put_intf(stream->intf);

        kfree(stream->format);
        kfree(stream->header.bmaControls);
        kfree(stream);
}

static struct uvc_streaming *uvc_stream_new(struct uvc_device *dev,
                                            struct usb_interface *intf)
{
        struct uvc_streaming *stream;

        stream = kzalloc(sizeof(*stream), GFP_KERNEL);
        if (stream == NULL)
                return NULL;

        mutex_init(&stream->mutex);

        stream->dev = dev;
        stream->intf = usb_get_intf(intf);
        stream->intfnum = intf->cur_altsetting->desc.bInterfaceNumber;

        /* Allocate a stream specific work queue for asynchronous tasks. */
        stream->async_wq = alloc_workqueue("uvcvideo", WQ_UNBOUND | WQ_HIGHPRI,
                                           0);
        if (!stream->async_wq) {
                uvc_stream_delete(stream);
                return NULL;
        }

        return stream;
}

/* ------------------------------------------------------------------------
 * Descriptors parsing
 */

static int uvc_parse_format(struct uvc_device *dev,
        struct uvc_streaming *streaming, struct uvc_format *format,
        u32 **intervals, unsigned char *buffer, int buflen)
{
        struct usb_interface *intf = streaming->intf;
        struct usb_host_interface *alts = intf->cur_altsetting;
        struct uvc_format_desc *fmtdesc;
        struct uvc_frame *frame;
        const unsigned char *start = buffer;
        unsigned int width_multiplier = 1;
        unsigned int interval;
        unsigned int i, n;
        u8 ftype;

        format->type = buffer[2];
        format->index = buffer[3];

        switch (buffer[2]) {
        case UVC_VS_FORMAT_UNCOMPRESSED:
        case UVC_VS_FORMAT_FRAME_BASED:
                n = buffer[2] == UVC_VS_FORMAT_UNCOMPRESSED ? 27 : 28;
                if (buflen < n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d FORMAT error\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                /* Find the format descriptor from its GUID. */
                fmtdesc = uvc_format_by_guid(&buffer[5]);

                if (fmtdesc != NULL) {
                        strscpy(format->name, fmtdesc->name,
                                sizeof(format->name));
                        format->fcc = fmtdesc->fcc;
                } else {
                        dev_info(&streaming->intf->dev,
                                 "Unknown video format %pUl\n", &buffer[5]);
                        snprintf(format->name, sizeof(format->name), "%pUl\n",
                                &buffer[5]);
                        format->fcc = 0;
                }

                format->bpp = buffer[21];

                /* Some devices report a format that doesn't match what they
                 * really send.
                 */
                if (dev->quirks & UVC_QUIRK_FORCE_Y8) {
                        if (format->fcc == V4L2_PIX_FMT_YUYV) {
                                strscpy(format->name, "Greyscale 8-bit (Y8  )",
                                        sizeof(format->name));
                                format->fcc = V4L2_PIX_FMT_GREY;
                                format->bpp = 8;
                                width_multiplier = 2;
                        }
                }

                /* Some devices report bpp that doesn't match the format. */
                if (dev->quirks & UVC_QUIRK_FORCE_BPP) {
                        const struct v4l2_format_info *info =
                                v4l2_format_info(format->fcc);

                        if (info) {
                                unsigned int div = info->hdiv * info->vdiv;

                                n = info->bpp[0] * div;
                                for (i = 1; i < info->comp_planes; i++)
                                        n += info->bpp[i];

                                format->bpp = DIV_ROUND_UP(8 * n, div);
                        }
                }

                if (buffer[2] == UVC_VS_FORMAT_UNCOMPRESSED) {
                        ftype = UVC_VS_FRAME_UNCOMPRESSED;
                } else {
                        ftype = UVC_VS_FRAME_FRAME_BASED;
                        if (buffer[27])
                                format->flags = UVC_FMT_FLAG_COMPRESSED;
                }
                break;

        case UVC_VS_FORMAT_MJPEG:
                if (buflen < 11) {
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d FORMAT error\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                strscpy(format->name, "MJPEG", sizeof(format->name));
                format->fcc = V4L2_PIX_FMT_MJPEG;
                format->flags = UVC_FMT_FLAG_COMPRESSED;
                format->bpp = 0;
                ftype = UVC_VS_FRAME_MJPEG;
                break;

        case UVC_VS_FORMAT_DV:
                if (buflen < 9) {
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d FORMAT error\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                switch (buffer[8] & 0x7f) {
                case 0:
                        strscpy(format->name, "SD-DV", sizeof(format->name));
                        break;
                case 1:
                        strscpy(format->name, "SDL-DV", sizeof(format->name));
                        break;
                case 2:
                        strscpy(format->name, "HD-DV", sizeof(format->name));
                        break;
                default:
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d: unknown DV format %u\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber, buffer[8]);
                        return -EINVAL;
                }

                strlcat(format->name, buffer[8] & (1 << 7) ? " 60Hz" : " 50Hz",
                        sizeof(format->name));

                format->fcc = V4L2_PIX_FMT_DV;
                format->flags = UVC_FMT_FLAG_COMPRESSED | UVC_FMT_FLAG_STREAM;
                format->bpp = 0;
                ftype = 0;

                /* Create a dummy frame descriptor. */
                frame = &format->frame[0];
                memset(&format->frame[0], 0, sizeof(format->frame[0]));
                frame->bFrameIntervalType = 1;
                frame->dwDefaultFrameInterval = 1;
                frame->dwFrameInterval = *intervals;
                *(*intervals)++ = 1;
                format->nframes = 1;
                break;

        case UVC_VS_FORMAT_MPEG2TS:
        case UVC_VS_FORMAT_STREAM_BASED:
                /* Not supported yet. */
        default:
                uvc_dbg(dev, DESCR,
                        "device %d videostreaming interface %d unsupported format %u\n",
                        dev->udev->devnum, alts->desc.bInterfaceNumber,
                        buffer[2]);
                return -EINVAL;
        }

        uvc_dbg(dev, DESCR, "Found format %s\n", format->name);

        buflen -= buffer[0];
        buffer += buffer[0];

        /* Parse the frame descriptors. Only uncompressed, MJPEG and frame
         * based formats have frame descriptors.
         */
        while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE &&
               buffer[2] == ftype) {
                frame = &format->frame[format->nframes];
                if (ftype != UVC_VS_FRAME_FRAME_BASED)
                        n = buflen > 25 ? buffer[25] : 0;
                else
                        n = buflen > 21 ? buffer[21] : 0;

                n = n ? n : 3;

                if (buflen < 26 + 4*n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d FRAME error\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                frame->bFrameIndex = buffer[3];
                frame->bmCapabilities = buffer[4];
                frame->wWidth = get_unaligned_le16(&buffer[5])
                              * width_multiplier;
                frame->wHeight = get_unaligned_le16(&buffer[7]);
                frame->dwMinBitRate = get_unaligned_le32(&buffer[9]);
                frame->dwMaxBitRate = get_unaligned_le32(&buffer[13]);
                if (ftype != UVC_VS_FRAME_FRAME_BASED) {
                        frame->dwMaxVideoFrameBufferSize =
                                get_unaligned_le32(&buffer[17]);
                        frame->dwDefaultFrameInterval =
                                get_unaligned_le32(&buffer[21]);
                        frame->bFrameIntervalType = buffer[25];
                } else {
                        frame->dwMaxVideoFrameBufferSize = 0;
                        frame->dwDefaultFrameInterval =
                                get_unaligned_le32(&buffer[17]);
                        frame->bFrameIntervalType = buffer[21];
                }
                frame->dwFrameInterval = *intervals;

                /* Several UVC chipsets screw up dwMaxVideoFrameBufferSize
                 * completely. Observed behaviours range from setting the
                 * value to 1.1x the actual frame size to hardwiring the
                 * 16 low bits to 0. This results in a higher than necessary
                 * memory usage as well as a wrong image size information. For
                 * uncompressed formats this can be fixed by computing the
                 * value from the frame size.
                 */
                if (!(format->flags & UVC_FMT_FLAG_COMPRESSED))
                        frame->dwMaxVideoFrameBufferSize = format->bpp
                                * frame->wWidth * frame->wHeight / 8;

                /* Some bogus devices report dwMinFrameInterval equal to
                 * dwMaxFrameInterval and have dwFrameIntervalStep set to
                 * zero. Setting all null intervals to 1 fixes the problem and
                 * some other divisions by zero that could happen.
                 */
                for (i = 0; i < n; ++i) {
                        interval = get_unaligned_le32(&buffer[26+4*i]);
                        *(*intervals)++ = interval ? interval : 1;
                }

                /* Make sure that the default frame interval stays between
                 * the boundaries.
                 */
                n -= frame->bFrameIntervalType ? 1 : 2;
                frame->dwDefaultFrameInterval =
                        min(frame->dwFrameInterval[n],
                            max(frame->dwFrameInterval[0],
                                frame->dwDefaultFrameInterval));

                if (dev->quirks & UVC_QUIRK_RESTRICT_FRAME_RATE) {
                        frame->bFrameIntervalType = 1;
                        frame->dwFrameInterval[0] =
                                frame->dwDefaultFrameInterval;
                }

                uvc_dbg(dev, DESCR, "- %ux%u (%u.%u fps)\n",
                        frame->wWidth, frame->wHeight,
                        10000000 / frame->dwDefaultFrameInterval,
                        (100000000 / frame->dwDefaultFrameInterval) % 10);

                format->nframes++;
                buflen -= buffer[0];
                buffer += buffer[0];
        }

        if (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE &&
            buffer[2] == UVC_VS_STILL_IMAGE_FRAME) {
                buflen -= buffer[0];
                buffer += buffer[0];
        }

        if (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE &&
            buffer[2] == UVC_VS_COLORFORMAT) {
                if (buflen < 6) {
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d COLORFORMAT error\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                format->colorspace = uvc_colorspace(buffer[3]);
                format->xfer_func = uvc_xfer_func(buffer[4]);
                format->ycbcr_enc = uvc_ycbcr_enc(buffer[5]);

                buflen -= buffer[0];
                buffer += buffer[0];
        }

        return buffer - start;
}

static int uvc_parse_streaming(struct uvc_device *dev,
        struct usb_interface *intf)
{
        struct uvc_streaming *streaming = NULL;
        struct uvc_format *format;
        struct uvc_frame *frame;
        struct usb_host_interface *alts = &intf->altsetting[0];
        unsigned char *_buffer, *buffer = alts->extra;
        int _buflen, buflen = alts->extralen;
        unsigned int nformats = 0, nframes = 0, nintervals = 0;
        unsigned int size, i, n, p;
        u32 *interval;
        u16 psize;
        int ret = -EINVAL;

        if (intf->cur_altsetting->desc.bInterfaceSubClass
                != UVC_SC_VIDEOSTREAMING) {
                uvc_dbg(dev, DESCR,
                        "device %d interface %d isn't a video streaming interface\n",
                        dev->udev->devnum,
                        intf->altsetting[0].desc.bInterfaceNumber);
                return -EINVAL;
        }

        if (usb_driver_claim_interface(&uvc_driver.driver, intf, dev)) {
                uvc_dbg(dev, DESCR,
                        "device %d interface %d is already claimed\n",
                        dev->udev->devnum,
                        intf->altsetting[0].desc.bInterfaceNumber);
                return -EINVAL;
        }

        streaming = uvc_stream_new(dev, intf);
        if (streaming == NULL) {
                usb_driver_release_interface(&uvc_driver.driver, intf);
                return -ENOMEM;
        }

        /* The Pico iMage webcam has its class-specific interface descriptors
         * after the endpoint descriptors.
         */
        if (buflen == 0) {
                for (i = 0; i < alts->desc.bNumEndpoints; ++i) {
                        struct usb_host_endpoint *ep = &alts->endpoint[i];

                        if (ep->extralen == 0)
                                continue;

                        if (ep->extralen > 2 &&
                            ep->extra[1] == USB_DT_CS_INTERFACE) {
                                uvc_dbg(dev, DESCR,
                                        "trying extra data from endpoint %u\n",
                                        i);
                                buffer = alts->endpoint[i].extra;
                                buflen = alts->endpoint[i].extralen;
                                break;
                        }
                }
        }

        /* Skip the standard interface descriptors. */
        while (buflen > 2 && buffer[1] != USB_DT_CS_INTERFACE) {
                buflen -= buffer[0];
                buffer += buffer[0];
        }

        if (buflen <= 2) {
                uvc_dbg(dev, DESCR,
                        "no class-specific streaming interface descriptors found\n");
                goto error;
        }

        /* Parse the header descriptor. */
        switch (buffer[2]) {
        case UVC_VS_OUTPUT_HEADER:
                streaming->type = V4L2_BUF_TYPE_VIDEO_OUTPUT;
                size = 9;
                break;

        case UVC_VS_INPUT_HEADER:
                streaming->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
                size = 13;
                break;

        default:
                uvc_dbg(dev, DESCR,
                        "device %d videostreaming interface %d HEADER descriptor not found\n",
                        dev->udev->devnum, alts->desc.bInterfaceNumber);
                goto error;
        }

        p = buflen >= 4 ? buffer[3] : 0;
        n = buflen >= size ? buffer[size-1] : 0;

        if (buflen < size + p*n) {
                uvc_dbg(dev, DESCR,
                        "device %d videostreaming interface %d HEADER descriptor is invalid\n",
                        dev->udev->devnum, alts->desc.bInterfaceNumber);
                goto error;
        }

        streaming->header.bNumFormats = p;
        streaming->header.bEndpointAddress = buffer[6];
        if (buffer[2] == UVC_VS_INPUT_HEADER) {
                streaming->header.bmInfo = buffer[7];
                streaming->header.bTerminalLink = buffer[8];
                streaming->header.bStillCaptureMethod = buffer[9];
                streaming->header.bTriggerSupport = buffer[10];
                streaming->header.bTriggerUsage = buffer[11];
        } else {
                streaming->header.bTerminalLink = buffer[7];
        }
        streaming->header.bControlSize = n;

        streaming->header.bmaControls = kmemdup(&buffer[size], p * n,
                                                GFP_KERNEL);
        if (streaming->header.bmaControls == NULL) {
                ret = -ENOMEM;
                goto error;
        }

        buflen -= buffer[0];
        buffer += buffer[0];

        _buffer = buffer;
        _buflen = buflen;

        /* Count the format and frame descriptors. */
        while (_buflen > 2 && _buffer[1] == USB_DT_CS_INTERFACE) {
                switch (_buffer[2]) {
                case UVC_VS_FORMAT_UNCOMPRESSED:
                case UVC_VS_FORMAT_MJPEG:
                case UVC_VS_FORMAT_FRAME_BASED:
                        nformats++;
                        break;

                case UVC_VS_FORMAT_DV:
                        /* DV format has no frame descriptor. We will create a
                         * dummy frame descriptor with a dummy frame interval.
                         */
                        nformats++;
                        nframes++;
                        nintervals++;
                        break;

                case UVC_VS_FORMAT_MPEG2TS:
                case UVC_VS_FORMAT_STREAM_BASED:
                        uvc_dbg(dev, DESCR,
                                "device %d videostreaming interface %d FORMAT %u is not supported\n",
                                dev->udev->devnum,
                                alts->desc.bInterfaceNumber, _buffer[2]);
                        break;

                case UVC_VS_FRAME_UNCOMPRESSED:
                case UVC_VS_FRAME_MJPEG:
                        nframes++;
                        if (_buflen > 25)
                                nintervals += _buffer[25] ? _buffer[25] : 3;
                        break;

                case UVC_VS_FRAME_FRAME_BASED:
                        nframes++;
                        if (_buflen > 21)
                                nintervals += _buffer[21] ? _buffer[21] : 3;
                        break;
                }

                _buflen -= _buffer[0];
                _buffer += _buffer[0];
        }

        if (nformats == 0) {
                uvc_dbg(dev, DESCR,
                        "device %d videostreaming interface %d has no supported formats defined\n",
                        dev->udev->devnum, alts->desc.bInterfaceNumber);
                goto error;
        }

        size = nformats * sizeof(*format) + nframes * sizeof(*frame)
             + nintervals * sizeof(*interval);
        format = kzalloc(size, GFP_KERNEL);
        if (format == NULL) {
                ret = -ENOMEM;
                goto error;
        }

        frame = (struct uvc_frame *)&format[nformats];
        interval = (u32 *)&frame[nframes];

        streaming->format = format;
        streaming->nformats = nformats;

        /* Parse the format descriptors. */
        while (buflen > 2 && buffer[1] == USB_DT_CS_INTERFACE) {
                switch (buffer[2]) {
                case UVC_VS_FORMAT_UNCOMPRESSED:
                case UVC_VS_FORMAT_MJPEG:
                case UVC_VS_FORMAT_DV:
                case UVC_VS_FORMAT_FRAME_BASED:
                        format->frame = frame;
                        ret = uvc_parse_format(dev, streaming, format,
                                &interval, buffer, buflen);
                        if (ret < 0)
                                goto error;

                        frame += format->nframes;
                        format++;

                        buflen -= ret;
                        buffer += ret;
                        continue;

                default:
                        break;
                }

                buflen -= buffer[0];
                buffer += buffer[0];
        }

        if (buflen)
                uvc_dbg(dev, DESCR,
                        "device %d videostreaming interface %d has %u bytes of trailing descriptor garbage\n",

                        dev->udev->devnum, alts->desc.bInterfaceNumber, buflen);

        /* Parse the alternate settings to find the maximum bandwidth. */
        for (i = 0; i < intf->num_altsetting; ++i) {
                struct usb_host_endpoint *ep;
                alts = &intf->altsetting[i];
                ep = uvc_find_endpoint(alts,
                                streaming->header.bEndpointAddress);
                if (ep == NULL)
                        continue;

                psize = le16_to_cpu(ep->desc.wMaxPacketSize);
                psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
                if (psize > streaming->maxpsize)
                        streaming->maxpsize = psize;
        }

        list_add_tail(&streaming->list, &dev->streams);
        return 0;

error:
        usb_driver_release_interface(&uvc_driver.driver, intf);
        uvc_stream_delete(streaming);
        return ret;
}

static const u8 uvc_camera_guid[16] = UVC_GUID_UVC_CAMERA;
static const u8 uvc_gpio_guid[16] = UVC_GUID_EXT_GPIO_CONTROLLER;
static const u8 uvc_media_transport_input_guid[16] =
        UVC_GUID_UVC_MEDIA_TRANSPORT_INPUT;
static const u8 uvc_processing_guid[16] = UVC_GUID_UVC_PROCESSING;

static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
                unsigned int num_pads, unsigned int extra_size)
{
        struct uvc_entity *entity;
        unsigned int num_inputs;
        unsigned int size;
        unsigned int i;

        extra_size = roundup(extra_size, sizeof(*entity->pads));
        if (num_pads)
                num_inputs = type & UVC_TERM_OUTPUT ? num_pads : num_pads - 1;
        else
                num_inputs = 0;
        size = sizeof(*entity) + extra_size + sizeof(*entity->pads) * num_pads
             + num_inputs;
        entity = kzalloc(size, GFP_KERNEL);
        if (entity == NULL)
                return NULL;

        entity->id = id;
        entity->type = type;

        /*
         * Set the GUID for standard entity types. For extension units, the GUID
         * is initialized by the caller.
         */
        switch (type) {
        case UVC_EXT_GPIO_UNIT:
                memcpy(entity->guid, uvc_gpio_guid, 16);
                break;
        case UVC_ITT_CAMERA:
                memcpy(entity->guid, uvc_camera_guid, 16);
                break;
        case UVC_ITT_MEDIA_TRANSPORT_INPUT:
                memcpy(entity->guid, uvc_media_transport_input_guid, 16);
                break;
        case UVC_VC_PROCESSING_UNIT:
                memcpy(entity->guid, uvc_processing_guid, 16);
                break;
        }

        entity->num_links = 0;
        entity->num_pads = num_pads;
        entity->pads = ((void *)(entity + 1)) + extra_size;

        for (i = 0; i < num_inputs; ++i)
                entity->pads[i].flags = MEDIA_PAD_FL_SINK;
        if (!UVC_ENTITY_IS_OTERM(entity) && num_pads)
                entity->pads[num_pads-1].flags = MEDIA_PAD_FL_SOURCE;

        entity->bNrInPins = num_inputs;
        entity->baSourceID = (u8 *)(&entity->pads[num_pads]);

        return entity;
}

/* Parse vendor-specific extensions. */
static int uvc_parse_vendor_control(struct uvc_device *dev,
        const unsigned char *buffer, int buflen)
{
        struct usb_device *udev = dev->udev;
        struct usb_host_interface *alts = dev->intf->cur_altsetting;
        struct uvc_entity *unit;
        unsigned int n, p;
        int handled = 0;

        switch (le16_to_cpu(dev->udev->descriptor.idVendor)) {
        case 0x046d:            /* Logitech */
                if (buffer[1] != 0x41 || buffer[2] != 0x01)
                        break;

                /* Logitech implements several vendor specific functions
                 * through vendor specific extension units (LXU).
                 *
                 * The LXU descriptors are similar to XU descriptors
                 * (see "USB Device Video Class for Video Devices", section
                 * 3.7.2.6 "Extension Unit Descriptor") with the following
                 * differences:
                 *
                 * ----------------------------------------------------------
                 * 0            bLength         1        Number
                 *      Size of this descriptor, in bytes: 24+p+n*2
                 * ----------------------------------------------------------
                 * 23+p+n       bmControlsType  N       Bitmap
                 *      Individual bits in the set are defined:
                 *      0: Absolute
                 *      1: Relative
                 *
                 *      This bitset is mapped exactly the same as bmControls.
                 * ----------------------------------------------------------
                 * 23+p+n*2     bReserved       1       Boolean
                 * ----------------------------------------------------------
                 * 24+p+n*2     iExtension      1       Index
                 *      Index of a string descriptor that describes this
                 *      extension unit.
                 * ----------------------------------------------------------
                 */
                p = buflen >= 22 ? buffer[21] : 0;
                n = buflen >= 25 + p ? buffer[22+p] : 0;

                if (buflen < 25 + p + 2*n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d EXTENSION_UNIT error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        break;
                }

                unit = uvc_alloc_entity(UVC_VC_EXTENSION_UNIT, buffer[3],
                                        p + 1, 2*n);
                if (unit == NULL)
                        return -ENOMEM;

                memcpy(unit->guid, &buffer[4], 16);
                unit->extension.bNumControls = buffer[20];
                memcpy(unit->baSourceID, &buffer[22], p);
                unit->extension.bControlSize = buffer[22+p];
                unit->extension.bmControls = (u8 *)unit + sizeof(*unit);
                unit->extension.bmControlsType = (u8 *)unit + sizeof(*unit)
                                               + n;
                memcpy(unit->extension.bmControls, &buffer[23+p], 2*n);

                if (buffer[24+p+2*n] != 0)
                        usb_string(udev, buffer[24+p+2*n], unit->name,
                                   sizeof(unit->name));
                else
                        sprintf(unit->name, "Extension %u", buffer[3]);

                list_add_tail(&unit->list, &dev->entities);
                handled = 1;
                break;
        }

        return handled;
}

static int uvc_parse_standard_control(struct uvc_device *dev,
        const unsigned char *buffer, int buflen)
{
        struct usb_device *udev = dev->udev;
        struct uvc_entity *unit, *term;
        struct usb_interface *intf;
        struct usb_host_interface *alts = dev->intf->cur_altsetting;
        unsigned int i, n, p, len;
        u16 type;

        switch (buffer[2]) {
        case UVC_VC_HEADER:
                n = buflen >= 12 ? buffer[11] : 0;

                if (buflen < 12 + n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d HEADER error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                dev->uvc_version = get_unaligned_le16(&buffer[3]);
                dev->clock_frequency = get_unaligned_le32(&buffer[7]);

                /* Parse all USB Video Streaming interfaces. */
                for (i = 0; i < n; ++i) {
                        intf = usb_ifnum_to_if(udev, buffer[12+i]);
                        if (intf == NULL) {
                                uvc_dbg(dev, DESCR,
                                        "device %d interface %d doesn't exists\n",
                                        udev->devnum, i);
                                continue;
                        }

                        uvc_parse_streaming(dev, intf);
                }
                break;

        case UVC_VC_INPUT_TERMINAL:
                if (buflen < 8) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d INPUT_TERMINAL error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                /*
                 * Reject invalid terminal types that would cause issues:
                 *
                 * - The high byte must be non-zero, otherwise it would be
                 *   confused with a unit.
                 *
                 * - Bit 15 must be 0, as we use it internally as a terminal
                 *   direction flag.
                 *
                 * Other unknown types are accepted.
                 */
                type = get_unaligned_le16(&buffer[4]);
                if ((type & 0x7f00) == 0 || (type & 0x8000) != 0) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d INPUT_TERMINAL %d has invalid type 0x%04x, skipping\n",
                                udev->devnum, alts->desc.bInterfaceNumber,
                                buffer[3], type);
                        return 0;
                }

                n = 0;
                p = 0;
                len = 8;

                if (type == UVC_ITT_CAMERA) {
                        n = buflen >= 15 ? buffer[14] : 0;
                        len = 15;

                } else if (type == UVC_ITT_MEDIA_TRANSPORT_INPUT) {
                        n = buflen >= 9 ? buffer[8] : 0;
                        p = buflen >= 10 + n ? buffer[9+n] : 0;
                        len = 10;
                }

                if (buflen < len + n + p) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d INPUT_TERMINAL error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                term = uvc_alloc_entity(type | UVC_TERM_INPUT, buffer[3],
                                        1, n + p);
                if (term == NULL)
                        return -ENOMEM;

                if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA) {
                        term->camera.bControlSize = n;
                        term->camera.bmControls = (u8 *)term + sizeof(*term);
                        term->camera.wObjectiveFocalLengthMin =
                                get_unaligned_le16(&buffer[8]);
                        term->camera.wObjectiveFocalLengthMax =
                                get_unaligned_le16(&buffer[10]);
                        term->camera.wOcularFocalLength =
                                get_unaligned_le16(&buffer[12]);
                        memcpy(term->camera.bmControls, &buffer[15], n);
                } else if (UVC_ENTITY_TYPE(term) ==
                           UVC_ITT_MEDIA_TRANSPORT_INPUT) {
                        term->media.bControlSize = n;
                        term->media.bmControls = (u8 *)term + sizeof(*term);
                        term->media.bTransportModeSize = p;
                        term->media.bmTransportModes = (u8 *)term
                                                     + sizeof(*term) + n;
                        memcpy(term->media.bmControls, &buffer[9], n);
                        memcpy(term->media.bmTransportModes, &buffer[10+n], p);
                }

                if (buffer[7] != 0)
                        usb_string(udev, buffer[7], term->name,
                                   sizeof(term->name));
                else if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
                        sprintf(term->name, "Camera %u", buffer[3]);
                else if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
                        sprintf(term->name, "Media %u", buffer[3]);
                else
                        sprintf(term->name, "Input %u", buffer[3]);

                list_add_tail(&term->list, &dev->entities);
                break;

        case UVC_VC_OUTPUT_TERMINAL:
                if (buflen < 9) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d OUTPUT_TERMINAL error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                /* Make sure the terminal type MSB is not null, otherwise it
                 * could be confused with a unit.
                 */
                type = get_unaligned_le16(&buffer[4]);
                if ((type & 0xff00) == 0) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d OUTPUT_TERMINAL %d has invalid type 0x%04x, skipping\n",
                                udev->devnum, alts->desc.bInterfaceNumber,
                                buffer[3], type);
                        return 0;
                }

                term = uvc_alloc_entity(type | UVC_TERM_OUTPUT, buffer[3],
                                        1, 0);
                if (term == NULL)
                        return -ENOMEM;

                memcpy(term->baSourceID, &buffer[7], 1);

                if (buffer[8] != 0)
                        usb_string(udev, buffer[8], term->name,
                                   sizeof(term->name));
                else
                        sprintf(term->name, "Output %u", buffer[3]);

                list_add_tail(&term->list, &dev->entities);
                break;

        case UVC_VC_SELECTOR_UNIT:
                p = buflen >= 5 ? buffer[4] : 0;

                if (buflen < 5 || buflen < 6 + p) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d SELECTOR_UNIT error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                unit = uvc_alloc_entity(buffer[2], buffer[3], p + 1, 0);
                if (unit == NULL)
                        return -ENOMEM;

                memcpy(unit->baSourceID, &buffer[5], p);

                if (buffer[5+p] != 0)
                        usb_string(udev, buffer[5+p], unit->name,
                                   sizeof(unit->name));
                else
                        sprintf(unit->name, "Selector %u", buffer[3]);

                list_add_tail(&unit->list, &dev->entities);
                break;

        case UVC_VC_PROCESSING_UNIT:
                n = buflen >= 8 ? buffer[7] : 0;
                p = dev->uvc_version >= 0x0110 ? 10 : 9;

                if (buflen < p + n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d PROCESSING_UNIT error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                unit = uvc_alloc_entity(buffer[2], buffer[3], 2, n);
                if (unit == NULL)
                        return -ENOMEM;

                memcpy(unit->baSourceID, &buffer[4], 1);
                unit->processing.wMaxMultiplier =
                        get_unaligned_le16(&buffer[5]);
                unit->processing.bControlSize = buffer[7];
                unit->processing.bmControls = (u8 *)unit + sizeof(*unit);
                memcpy(unit->processing.bmControls, &buffer[8], n);
                if (dev->uvc_version >= 0x0110)
                        unit->processing.bmVideoStandards = buffer[9+n];

                if (buffer[8+n] != 0)
                        usb_string(udev, buffer[8+n], unit->name,
                                   sizeof(unit->name));
                else
                        sprintf(unit->name, "Processing %u", buffer[3]);

                list_add_tail(&unit->list, &dev->entities);
                break;

        case UVC_VC_EXTENSION_UNIT:
                p = buflen >= 22 ? buffer[21] : 0;
                n = buflen >= 24 + p ? buffer[22+p] : 0;

                if (buflen < 24 + p + n) {
                        uvc_dbg(dev, DESCR,
                                "device %d videocontrol interface %d EXTENSION_UNIT error\n",
                                udev->devnum, alts->desc.bInterfaceNumber);
                        return -EINVAL;
                }

                unit = uvc_alloc_entity(buffer[2], buffer[3], p + 1, n);
                if (unit == NULL)
                        return -ENOMEM;

                memcpy(unit->guid, &buffer[4], 16);
                unit->extension.bNumControls = buffer[20];
                memcpy(unit->baSourceID, &buffer[22], p);
                unit->extension.bControlSize = buffer[22+p];
                unit->extension.bmControls = (u8 *)unit + sizeof(*unit);
                memcpy(unit->extension.bmControls, &buffer[23+p], n);

                if (buffer[23+p+n] != 0)
                        usb_string(udev, buffer[23+p+n], unit->name,
                                   sizeof(unit->name));
                else
                        sprintf(unit->name, "Extension %u", buffer[3]);

                list_add_tail(&unit->list, &dev->entities);
                break;

        default:
                uvc_dbg(dev, DESCR,
                        "Found an unknown CS_INTERFACE descriptor (%u)\n",
                        buffer[2]);
                break;
        }

        return 0;
}

static int uvc_parse_control(struct uvc_device *dev)
{
        struct usb_host_interface *alts = dev->intf->cur_altsetting;
        unsigned char *buffer = alts->extra;
        int buflen = alts->extralen;
        int ret;

        /* Parse the default alternate setting only, as the UVC specification
         * defines a single alternate setting, the default alternate setting
         * zero.
         */

        while (buflen > 2) {
                if (uvc_parse_vendor_control(dev, buffer, buflen) ||
                    buffer[1] != USB_DT_CS_INTERFACE)
                        goto next_descriptor;

                if ((ret = uvc_parse_standard_control(dev, buffer, buflen)) < 0)
                        return ret;

next_descriptor:
                buflen -= buffer[0];
                buffer += buffer[0];
        }

        /* Check if the optional status endpoint is present. Built-in iSight
         * webcams have an interrupt endpoint but spit proprietary data that
         * don't conform to the UVC status endpoint messages. Don't try to
         * handle the interrupt endpoint for those cameras.
         */
        if (alts->desc.bNumEndpoints == 1 &&
            !(dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)) {
                struct usb_host_endpoint *ep = &alts->endpoint[0];
                struct usb_endpoint_descriptor *desc = &ep->desc;

                if (usb_endpoint_is_int_in(desc) &&
                    le16_to_cpu(desc->wMaxPacketSize) >= 8 &&
                    desc->bInterval != 0) {
                        uvc_dbg(dev, DESCR,
                                "Found a Status endpoint (addr %02x)\n",
                                desc->bEndpointAddress);
                        dev->int_ep = ep;
                }
        }

        return 0;
}

/* -----------------------------------------------------------------------------
 * Privacy GPIO
 */

static void uvc_gpio_event(struct uvc_device *dev)
{
        struct uvc_entity *unit = dev->gpio_unit;
        struct uvc_video_chain *chain;
        u8 new_val;

        if (!unit)
                return;

        new_val = gpiod_get_value_cansleep(unit->gpio.gpio_privacy);

        /* GPIO entities are always on the first chain. */
        chain = list_first_entry(&dev->chains, struct uvc_video_chain, list);
        uvc_ctrl_status_event(chain, unit->controls, &new_val);
}

static int uvc_gpio_get_cur(struct uvc_device *dev, struct uvc_entity *entity,
                            u8 cs, void *data, u16 size)
{
        if (cs != UVC_CT_PRIVACY_CONTROL || size < 1)
                return -EINVAL;

        *(u8 *)data = gpiod_get_value_cansleep(entity->gpio.gpio_privacy);

        return 0;
}

static int uvc_gpio_get_info(struct uvc_device *dev, struct uvc_entity *entity,
                             u8 cs, u8 *caps)
{
        if (cs != UVC_CT_PRIVACY_CONTROL)
                return -EINVAL;

        *caps = UVC_CONTROL_CAP_GET | UVC_CONTROL_CAP_AUTOUPDATE;
        return 0;
}

static irqreturn_t uvc_gpio_irq(int irq, void *data)
{
        struct uvc_device *dev = data;

        uvc_gpio_event(dev);
        return IRQ_HANDLED;
}

static int uvc_gpio_parse(struct uvc_device *dev)
{
        struct uvc_entity *unit;
        struct gpio_desc *gpio_privacy;
        int irq;

        gpio_privacy = devm_gpiod_get_optional(&dev->udev->dev, "privacy",
                                               GPIOD_IN);
        if (IS_ERR_OR_NULL(gpio_privacy))
                return PTR_ERR_OR_ZERO(gpio_privacy);

        unit = uvc_alloc_entity(UVC_EXT_GPIO_UNIT, UVC_EXT_GPIO_UNIT_ID, 0, 1);
        if (!unit)
                return -ENOMEM;

        irq = gpiod_to_irq(gpio_privacy);
        if (irq < 0) {
                if (irq != EPROBE_DEFER)
                        dev_err(&dev->udev->dev,
                                "No IRQ for privacy GPIO (%d)\n", irq);
                return irq;
        }

        unit->gpio.gpio_privacy = gpio_privacy;
        unit->gpio.irq = irq;
        unit->gpio.bControlSize = 1;
        unit->gpio.bmControls = (u8 *)unit + sizeof(*unit);
        unit->gpio.bmControls[0] = 1;
        unit->get_cur = uvc_gpio_get_cur;
        unit->get_info = uvc_gpio_get_info;
        strscpy(unit->name, "GPIO", sizeof(unit->name));

        list_add_tail(&unit->list, &dev->entities);

        dev->gpio_unit = unit;

        return 0;
}

static int uvc_gpio_init_irq(struct uvc_device *dev)
{
        struct uvc_entity *unit = dev->gpio_unit;

        if (!unit || unit->gpio.irq < 0)
                return 0;

        return devm_request_threaded_irq(&dev->udev->dev, unit->gpio.irq, NULL,
                                         uvc_gpio_irq,
                                         IRQF_ONESHOT | IRQF_TRIGGER_FALLING |
                                         IRQF_TRIGGER_RISING,
                                         "uvc_privacy_gpio", dev);
}

/* ------------------------------------------------------------------------
 * UVC device scan
 */

/*
 * Scan the UVC descriptors to locate a chain starting at an Output Terminal
 * and containing the following units:
 *
 * - one or more Output Terminals (USB Streaming or Display)
 * - zero or one Processing Unit
 * - zero, one or more single-input Selector Units
 * - zero or one multiple-input Selector Units, provided all inputs are
 *   connected to input terminals
 * - zero, one or mode single-input Extension Units
 * - one or more Input Terminals (Camera, External or USB Streaming)
 *
 * The terminal and units must match on of the following structures:
 *
 * ITT_*(0) -> +---------+    +---------+    +---------+ -> TT_STREAMING(0)
 * ...         | SU{0,1} | -> | PU{0,1} | -> | XU{0,n} |    ...
 * ITT_*(n) -> +---------+    +---------+    +---------+ -> TT_STREAMING(n)
 *
 *                 +---------+    +---------+ -> OTT_*(0)
 * TT_STREAMING -> | PU{0,1} | -> | XU{0,n} |    ...
 *                 +---------+    +---------+ -> OTT_*(n)
 *
 * The Processing Unit and Extension Units can be in any order. Additional
 * Extension Units connected to the main chain as single-unit branches are
 * also supported. Single-input Selector Units are ignored.
 */
static int uvc_scan_chain_entity(struct uvc_video_chain *chain,
        struct uvc_entity *entity)
{
        switch (UVC_ENTITY_TYPE(entity)) {
        case UVC_VC_EXTENSION_UNIT:
                uvc_dbg_cont(PROBE, " <- XU %d", entity->id);

                if (entity->bNrInPins != 1) {
                        uvc_dbg(chain->dev, DESCR,
                                "Extension unit %d has more than 1 input pin\n",
                                entity->id);
                        return -1;
                }

                break;

        case UVC_VC_PROCESSING_UNIT:
                uvc_dbg_cont(PROBE, " <- PU %d", entity->id);

                if (chain->processing != NULL) {
                        uvc_dbg(chain->dev, DESCR,
                                "Found multiple Processing Units in chain\n");
                        return -1;
                }

                chain->processing = entity;
                break;

        case UVC_VC_SELECTOR_UNIT:
                uvc_dbg_cont(PROBE, " <- SU %d", entity->id);

                /* Single-input selector units are ignored. */
                if (entity->bNrInPins == 1)
                        break;

                if (chain->selector != NULL) {
                        uvc_dbg(chain->dev, DESCR,
                                "Found multiple Selector Units in chain\n");
                        return -1;
                }

                chain->selector = entity;
                break;

        case UVC_ITT_VENDOR_SPECIFIC:
        case UVC_ITT_CAMERA:
        case UVC_ITT_MEDIA_TRANSPORT_INPUT:
                uvc_dbg_cont(PROBE, " <- IT %d\n", entity->id);

                break;

        case UVC_OTT_VENDOR_SPECIFIC:
        case UVC_OTT_DISPLAY:
        case UVC_OTT_MEDIA_TRANSPORT_OUTPUT:
                uvc_dbg_cont(PROBE, " OT %d", entity->id);

                break;

        case UVC_TT_STREAMING:
                if (UVC_ENTITY_IS_ITERM(entity))
                        uvc_dbg_cont(PROBE, " <- IT %d\n", entity->id);
                else
                        uvc_dbg_cont(PROBE, " OT %d", entity->id);

                break;

        default:
                uvc_dbg(chain->dev, DESCR,
                        "Unsupported entity type 0x%04x found in chain\n",
                        UVC_ENTITY_TYPE(entity));
                return -1;
        }

        list_add_tail(&entity->chain, &chain->entities);
        return 0;
}

static int uvc_scan_chain_forward(struct uvc_video_chain *chain,
        struct uvc_entity *entity, struct uvc_entity *prev)
{
        struct uvc_entity *forward;
        int found;

        /* Forward scan */
        forward = NULL;
        found = 0;

        while (1) {
                forward = uvc_entity_by_reference(chain->dev, entity->id,
                        forward);
                if (forward == NULL)
                        break;
                if (forward == prev)
                        continue;
                if (forward->chain.next || forward->chain.prev) {
                        uvc_dbg(chain->dev, DESCR,
                                "Found reference to entity %d already in chain\n",
                                forward->id);
                        return -EINVAL;
                }

                switch (UVC_ENTITY_TYPE(forward)) {
                case UVC_VC_EXTENSION_UNIT:
                        if (forward->bNrInPins != 1) {
                                uvc_dbg(chain->dev, DESCR,
                                        "Extension unit %d has more than 1 input pin\n",
                                        forward->id);
                                return -EINVAL;
                        }

                        /*
                         * Some devices reference an output terminal as the
                         * source of extension units. This is incorrect, as
                         * output terminals only have an input pin, and thus
                         * can't be connected to any entity in the forward
                         * direction. The resulting topology would cause issues
                         * when registering the media controller graph. To
                         * avoid this problem, connect the extension unit to
                         * the source of the output terminal instead.
                         */
                        if (UVC_ENTITY_IS_OTERM(entity)) {
                                struct uvc_entity *source;

                                source = uvc_entity_by_id(chain->dev,
                                                          entity->baSourceID[0]);
                                if (!source) {
                                        uvc_dbg(chain->dev, DESCR,
                                                "Can't connect extension unit %u in chain\n",
                                                forward->id);
                                        break;
                                }

                                forward->baSourceID[0] = source->id;
                        }

                        list_add_tail(&forward->chain, &chain->entities);
                        if (!found)
                                uvc_dbg_cont(PROBE, " (->");

                        uvc_dbg_cont(PROBE, " XU %d", forward->id);
                        found = 1;
                        break;

                case UVC_OTT_VENDOR_SPECIFIC:
                case UVC_OTT_DISPLAY:
                case UVC_OTT_MEDIA_TRANSPORT_OUTPUT:
                case UVC_TT_STREAMING:
                        if (UVC_ENTITY_IS_ITERM(forward)) {
                                uvc_dbg(chain->dev, DESCR,
                                        "Unsupported input terminal %u\n",
                                        forward->id);
                                return -EINVAL;
                        }

                        if (UVC_ENTITY_IS_OTERM(entity)) {
                                uvc_dbg(chain->dev, DESCR,
                                        "Unsupported connection between output terminals %u and %u\n",
                                        entity->id, forward->id);
                                break;
                        }

                        list_add_tail(&forward->chain, &chain->entities);
                        if (!found)
                                uvc_dbg_cont(PROBE, " (->");

                        uvc_dbg_cont(PROBE, " OT %d", forward->id);
                        found = 1;
                        break;
                }
        }
        if (found)
                uvc_dbg_cont(PROBE, ")");

        return 0;
}

static int uvc_scan_chain_backward(struct uvc_video_chain *chain,
        struct uvc_entity **_entity)
{
        struct uvc_entity *entity = *_entity;
        struct uvc_entity *term;
        int id = -EINVAL, i;

        switch (UVC_ENTITY_TYPE(entity)) {
        case UVC_VC_EXTENSION_UNIT:
        case UVC_VC_PROCESSING_UNIT:
                id = entity->baSourceID[0];
                break;

        case UVC_VC_SELECTOR_UNIT:
                /* Single-input selector units are ignored. */
                if (entity->bNrInPins == 1) {
                        id = entity->baSourceID[0];
                        break;
                }

                uvc_dbg_cont(PROBE, " <- IT");

                chain->selector = entity;
                for (i = 0; i < entity->bNrInPins; ++i) {
                        id = entity->baSourceID[i];
                        term = uvc_entity_by_id(chain->dev, id);
                        if (term == NULL || !UVC_ENTITY_IS_ITERM(term)) {
                                uvc_dbg(chain->dev, DESCR,
                                        "Selector unit %d input %d isn't connected to an input terminal\n",
                                        entity->id, i);
                                return -1;
                        }

                        if (term->chain.next || term->chain.prev) {
                                uvc_dbg(chain->dev, DESCR,
                                        "Found reference to entity %d already in chain\n",
                                        term->id);
                                return -EINVAL;
                        }

                        uvc_dbg_cont(PROBE, " %d", term->id);

                        list_add_tail(&term->chain, &chain->entities);
                        uvc_scan_chain_forward(chain, term, entity);
                }

                uvc_dbg_cont(PROBE, "\n");

                id = 0;
                break;

        case UVC_ITT_VENDOR_SPECIFIC:
        case UVC_ITT_CAMERA:
        case UVC_ITT_MEDIA_TRANSPORT_INPUT:
        case UVC_OTT_VENDOR_SPECIFIC:
        case UVC_OTT_DISPLAY:
        case UVC_OTT_MEDIA_TRANSPORT_OUTPUT:
        case UVC_TT_STREAMING:
                id = UVC_ENTITY_IS_OTERM(entity) ? entity->baSourceID[0] : 0;
                break;
        }

        if (id <= 0) {
                *_entity = NULL;
                return id;
        }

        entity = uvc_entity_by_id(chain->dev, id);
        if (entity == NULL) {
                uvc_dbg(chain->dev, DESCR,
                        "Found reference to unknown entity %d\n", id);
                return -EINVAL;
        }

        *_entity = entity;
        return 0;
}

static int uvc_scan_chain(struct uvc_video_chain *chain,
                          struct uvc_entity *term)
{
        struct uvc_entity *entity, *prev;

        uvc_dbg(chain->dev, PROBE, "Scanning UVC chain:");

        entity = term;
        prev = NULL;

        while (entity != NULL) {
                /* Entity must not be part of an existing chain */
                if (entity->chain.next || entity->chain.prev) {
                        uvc_dbg(chain->dev, DESCR,
                                "Found reference to entity %d already in chain\n",
                                entity->id);
                        return -EINVAL;
                }

                /* Process entity */
                if (uvc_scan_chain_entity(chain, entity) < 0)
                        return -EINVAL;

                /* Forward scan */
                if (uvc_scan_chain_forward(chain, entity, prev) < 0)
                        return -EINVAL;

                /* Backward scan */
                prev = entity;
                if (uvc_scan_chain_backward(chain, &entity) < 0)
                        return -EINVAL;
        }

        return 0;
}

static unsigned int uvc_print_terms(struct list_head *terms, u16 dir,
                char *buffer)
{
        struct uvc_entity *term;
        unsigned int nterms = 0;
        char *p = buffer;

        list_for_each_entry(term, terms, chain) {
                if (!UVC_ENTITY_IS_TERM(term) ||
                    UVC_TERM_DIRECTION(term) != dir)
                        continue;

                if (nterms)
                        p += sprintf(p, ",");
                if (++nterms >= 4) {
                        p += sprintf(p, "...");
                        break;
                }
                p += sprintf(p, "%u", term->id);
        }

        return p - buffer;
}

static const char *uvc_print_chain(struct uvc_video_chain *chain)
{
        static char buffer[43];
        char *p = buffer;

        p += uvc_print_terms(&chain->entities, UVC_TERM_INPUT, p);
        p += sprintf(p, " -> ");
        uvc_print_terms(&chain->entities, UVC_TERM_OUTPUT, p);

        return buffer;
}

static struct uvc_video_chain *uvc_alloc_chain(struct uvc_device *dev)
{
        struct uvc_video_chain *chain;

        chain = kzalloc(sizeof(*chain), GFP_KERNEL);
        if (chain == NULL)
                return NULL;

        INIT_LIST_HEAD(&chain->entities);
        mutex_init(&chain->ctrl_mutex);
        chain->dev = dev;
        v4l2_prio_init(&chain->prio);

        return chain;
}

/*
 * Fallback heuristic for devices that don't connect units and terminals in a
 * valid chain.
 *
 * Some devices have invalid baSourceID references, causing uvc_scan_chain()
 * to fail, but if we just take the entities we can find and put them together
 * in the most sensible chain we can think of, turns out they do work anyway.
 * Note: This heuristic assumes there is a single chain.
 *
 * At the time of writing, devices known to have such a broken chain are
 *  - Acer Integrated Camera (5986:055a)
 *  - Realtek rtl157a7 (0bda:57a7)
 */
static int uvc_scan_fallback(struct uvc_device *dev)
{
        struct uvc_video_chain *chain;
        struct uvc_entity *iterm = NULL;
        struct uvc_entity *oterm = NULL;
        struct uvc_entity *entity;
        struct uvc_entity *prev;

        /*
         * Start by locating the input and output terminals. We only support
         * devices with exactly one of each for now.
         */
        list_for_each_entry(entity, &dev->entities, list) {
                if (UVC_ENTITY_IS_ITERM(entity)) {
                        if (iterm)
                                return -EINVAL;
                        iterm = entity;
                }

                if (UVC_ENTITY_IS_OTERM(entity)) {
                        if (oterm)
                                return -EINVAL;
                        oterm = entity;
                }
        }

        if (iterm == NULL || oterm == NULL)
                return -EINVAL;

        /* Allocate the chain and fill it. */
        chain = uvc_alloc_chain(dev);
        if (chain == NULL)
                return -ENOMEM;

        if (uvc_scan_chain_entity(chain, oterm) < 0)
                goto error;