/*
 * Driver for MT9T031 CMOS Image Sensor from Micron
 *
 * Copyright (C) 2008, Guennadi Liakhovetski, DENX Software Engineering <lg@denx.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/videodev2.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/log2.h>

#include <media/v4l2-subdev.h>
#include <media/v4l2-chip-ident.h>
#include <media/soc_camera.h>

/* mt9t031 i2c address 0x5d
 * The platform has to define i2c_board_info and link to it from
 * struct soc_camera_link */

/* mt9t031 selected register addresses */
#define MT9T031_CHIP_VERSION            0x00
#define MT9T031_ROW_START               0x01
#define MT9T031_COLUMN_START            0x02
#define MT9T031_WINDOW_HEIGHT           0x03
#define MT9T031_WINDOW_WIDTH            0x04
#define MT9T031_HORIZONTAL_BLANKING     0x05
#define MT9T031_VERTICAL_BLANKING       0x06
#define MT9T031_OUTPUT_CONTROL          0x07
#define MT9T031_SHUTTER_WIDTH_UPPER     0x08
#define MT9T031_SHUTTER_WIDTH           0x09
#define MT9T031_PIXEL_CLOCK_CONTROL     0x0a
#define MT9T031_FRAME_RESTART           0x0b
#define MT9T031_SHUTTER_DELAY           0x0c
#define MT9T031_RESET                   0x0d
#define MT9T031_READ_MODE_1             0x1e
#define MT9T031_READ_MODE_2             0x20
#define MT9T031_READ_MODE_3             0x21
#define MT9T031_ROW_ADDRESS_MODE        0x22
#define MT9T031_COLUMN_ADDRESS_MODE     0x23
#define MT9T031_GLOBAL_GAIN             0x35
#define MT9T031_CHIP_ENABLE             0xF8

#define MT9T031_MAX_HEIGHT              1536
#define MT9T031_MAX_WIDTH               2048
#define MT9T031_MIN_HEIGHT              2
#define MT9T031_MIN_WIDTH               18
#define MT9T031_HORIZONTAL_BLANK        142
#define MT9T031_VERTICAL_BLANK          25
#define MT9T031_COLUMN_SKIP             32
#define MT9T031_ROW_SKIP                20

#define MT9T031_BUS_PARAM       (SOCAM_PCLK_SAMPLE_RISING |     \
        SOCAM_PCLK_SAMPLE_FALLING | SOCAM_HSYNC_ACTIVE_HIGH |   \
        SOCAM_VSYNC_ACTIVE_HIGH | SOCAM_DATA_ACTIVE_HIGH |      \
        SOCAM_MASTER | SOCAM_DATAWIDTH_10)

static const struct soc_camera_data_format mt9t031_colour_formats[] = {
        {
                .name           = "Bayer (sRGB) 10 bit",
                .depth          = 10,
                .fourcc         = V4L2_PIX_FMT_SGRBG10,
                .colorspace     = V4L2_COLORSPACE_SRGB,
        }
};

struct mt9t031 {
        struct v4l2_subdev subdev;
        struct v4l2_rect rect;  /* Sensor window */
        int model;      /* V4L2_IDENT_MT9T031* codes from v4l2-chip-ident.h */
        u16 xskip;
        u16 yskip;
        unsigned int gain;
        unsigned int exposure;
        unsigned char autoexposure;
};

static struct mt9t031 *to_mt9t031(const struct i2c_client *client)
{
        return container_of(i2c_get_clientdata(client), struct mt9t031, subdev);
}

static int reg_read(struct i2c_client *client, const u8 reg)
{
        s32 data = i2c_smbus_read_word_data(client, reg);
        return data < 0 ? data : swab16(data);
}

static int reg_write(struct i2c_client *client, const u8 reg,
                     const u16 data)
{
        return i2c_smbus_write_word_data(client, reg, swab16(data));
}

static int reg_set(struct i2c_client *client, const u8 reg,
                   const u16 data)
{
        int ret;

        ret = reg_read(client, reg);
        if (ret < 0)
                return ret;
        return reg_write(client, reg, ret | data);
}

static int reg_clear(struct i2c_client *client, const u8 reg,
                     const u16 data)
{
        int ret;

        ret = reg_read(client, reg);
        if (ret < 0)
                return ret;
        return reg_write(client, reg, ret & ~data);
}

static int set_shutter(struct i2c_client *client, const u32 data)
{
        int ret;

        ret = reg_write(client, MT9T031_SHUTTER_WIDTH_UPPER, data >> 16);

        if (ret >= 0)
                ret = reg_write(client, MT9T031_SHUTTER_WIDTH, data & 0xffff);

        return ret;
}

static int get_shutter(struct i2c_client *client, u32 *data)
{
        int ret;

        ret = reg_read(client, MT9T031_SHUTTER_WIDTH_UPPER);
        *data = ret << 16;

        if (ret >= 0)
                ret = reg_read(client, MT9T031_SHUTTER_WIDTH);
        *data |= ret & 0xffff;

        return ret < 0 ? ret : 0;
}

static int mt9t031_idle(struct i2c_client *client)
{
        int ret;

        /* Disable chip output, synchronous option update */
        ret = reg_write(client, MT9T031_RESET, 1);
        if (ret >= 0)
                ret = reg_write(client, MT9T031_RESET, 0);
        if (ret >= 0)
                ret = reg_clear(client, MT9T031_OUTPUT_CONTROL, 2);

        return ret >= 0 ? 0 : -EIO;
}

static int mt9t031_disable(struct i2c_client *client)
{
        /* Disable the chip */
        reg_clear(client, MT9T031_OUTPUT_CONTROL, 2);

        return 0;
}

static int mt9t031_s_stream(struct v4l2_subdev *sd, int enable)
{
        struct i2c_client *client = sd->priv;
        int ret;

        if (enable)
                /* Switch to master "normal" mode */
                ret = reg_set(client, MT9T031_OUTPUT_CONTROL, 2);
        else
                /* Stop sensor readout */
                ret = reg_clear(client, MT9T031_OUTPUT_CONTROL, 2);

        if (ret < 0)
                return -EIO;

        return 0;
}

static int mt9t031_set_bus_param(struct soc_camera_device *icd,
                                 unsigned long flags)
{
        struct i2c_client *client = to_i2c_client(to_soc_camera_control(icd));

        /* The caller should have queried our parameters, check anyway */
        if (flags & ~MT9T031_BUS_PARAM)
                return -EINVAL;

        if (flags & SOCAM_PCLK_SAMPLE_FALLING)
                reg_clear(client, MT9T031_PIXEL_CLOCK_CONTROL, 0x8000);
        else
                reg_set(client, MT9T031_PIXEL_CLOCK_CONTROL, 0x8000);

        return 0;
}

static unsigned long mt9t031_query_bus_param(struct soc_camera_device *icd)
{
        struct soc_camera_link *icl = to_soc_camera_link(icd);

        return soc_camera_apply_sensor_flags(icl, MT9T031_BUS_PARAM);
}

/* target must be _even_ */
static u16 mt9t031_skip(s32 *source, s32 target, s32 max)
{
        unsigned int skip;

        if (*source < target + target / 2) {
                *source = target;
                return 1;
        }

        skip = min(max, *source + target / 2) / target;
        if (skip > 8)
                skip = 8;
        *source = target * skip;

        return skip;
}

/* rect is the sensor rectangle, the caller guarantees parameter validity */
static int mt9t031_set_params(struct soc_camera_device *icd,
                              struct v4l2_rect *rect, u16 xskip, u16 yskip)
{
        struct i2c_client *client = to_i2c_client(to_soc_camera_control(icd));
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        int ret;
        u16 xbin, ybin;
        const u16 hblank = MT9T031_HORIZONTAL_BLANK,
                vblank = MT9T031_VERTICAL_BLANK;

        xbin = min(xskip, (u16)3);
        ybin = min(yskip, (u16)3);

        /*
         * Could just do roundup(rect->left, [xy]bin * 2); but this is cheaper.
         * There is always a valid suitably aligned value. The worst case is
         * xbin = 3, width = 2048. Then we will start at 36, the last read out
         * pixel will be 2083, which is < 2085 - first black pixel.
         *
         * MT9T031 datasheet imposes window left border alignment, depending on
         * the selected xskip. Failing to conform to this requirement produces
         * dark horizontal stripes in the image. However, even obeying to this
         * requirement doesn't eliminate the stripes in all configurations. They
         * appear "locally reproducibly," but can differ between tests under
         * different lighting conditions.
         */
        switch (xbin) {
        case 1:
                rect->left &= ~1;
                break;
        case 2:
                rect->left &= ~3;
                break;
        case 3:
                rect->left = rect->left > roundup(MT9T031_COLUMN_SKIP, 6) ?
                        (rect->left / 6) * 6 : roundup(MT9T031_COLUMN_SKIP, 6);
        }

        rect->top &= ~1;

        dev_dbg(&client->dev, "skip %u:%u, rect %ux%u@%u:%u\n",
                xskip, yskip, rect->width, rect->height, rect->left, rect->top);

        /* Disable register update, reconfigure atomically */
        ret = reg_set(client, MT9T031_OUTPUT_CONTROL, 1);
        if (ret < 0)
                return ret;

        /* Blanking and start values - default... */
        ret = reg_write(client, MT9T031_HORIZONTAL_BLANKING, hblank);
        if (ret >= 0)
                ret = reg_write(client, MT9T031_VERTICAL_BLANKING, vblank);

        if (yskip != mt9t031->yskip || xskip != mt9t031->xskip) {
                /* Binning, skipping */
                if (ret >= 0)
                        ret = reg_write(client, MT9T031_COLUMN_ADDRESS_MODE,
                                        ((xbin - 1) << 4) | (xskip - 1));
                if (ret >= 0)
                        ret = reg_write(client, MT9T031_ROW_ADDRESS_MODE,
                                        ((ybin - 1) << 4) | (yskip - 1));
        }
        dev_dbg(&client->dev, "new physical left %u, top %u\n",
                rect->left, rect->top);

        /* The caller provides a supported format, as guaranteed by
         * icd->try_fmt_cap(), soc_camera_s_crop() and soc_camera_cropcap() */
        if (ret >= 0)
                ret = reg_write(client, MT9T031_COLUMN_START, rect->left);
        if (ret >= 0)
                ret = reg_write(client, MT9T031_ROW_START, rect->top);
        if (ret >= 0)
                ret = reg_write(client, MT9T031_WINDOW_WIDTH, rect->width - 1);
        if (ret >= 0)
                ret = reg_write(client, MT9T031_WINDOW_HEIGHT,
                                rect->height + icd->y_skip_top - 1);
        if (ret >= 0 && mt9t031->autoexposure) {
                unsigned int total_h = rect->height + icd->y_skip_top + vblank;
                ret = set_shutter(client, total_h);
                if (ret >= 0) {
                        const u32 shutter_max = MT9T031_MAX_HEIGHT + vblank;
                        const struct v4l2_queryctrl *qctrl =
                                soc_camera_find_qctrl(icd->ops,
                                                      V4L2_CID_EXPOSURE);
                        mt9t031->exposure = (shutter_max / 2 + (total_h - 1) *
                                 (qctrl->maximum - qctrl->minimum)) /
                                shutter_max + qctrl->minimum;
                }
        }

        /* Re-enable register update, commit all changes */
        if (ret >= 0)
                ret = reg_clear(client, MT9T031_OUTPUT_CONTROL, 1);

        if (ret >= 0) {
                mt9t031->rect = *rect;
                mt9t031->xskip = xskip;
                mt9t031->yskip = yskip;
        }

        return ret < 0 ? ret : 0;
}

static int mt9t031_s_crop(struct v4l2_subdev *sd, struct v4l2_crop *a)
{
        struct v4l2_rect rect = a->c;
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        struct soc_camera_device *icd = client->dev.platform_data;

        rect.width = ALIGN(rect.width, 2);
        rect.height = ALIGN(rect.height, 2);

        soc_camera_limit_side(&rect.left, &rect.width,
                     MT9T031_COLUMN_SKIP, MT9T031_MIN_WIDTH, MT9T031_MAX_WIDTH);

        soc_camera_limit_side(&rect.top, &rect.height,
                     MT9T031_ROW_SKIP, MT9T031_MIN_HEIGHT, MT9T031_MAX_HEIGHT);

        return mt9t031_set_params(icd, &rect, mt9t031->xskip, mt9t031->yskip);
}

static int mt9t031_g_crop(struct v4l2_subdev *sd, struct v4l2_crop *a)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);

        a->c    = mt9t031->rect;
        a->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        return 0;
}

static int mt9t031_cropcap(struct v4l2_subdev *sd, struct v4l2_cropcap *a)
{
        a->bounds.left                  = MT9T031_COLUMN_SKIP;
        a->bounds.top                   = MT9T031_ROW_SKIP;
        a->bounds.width                 = MT9T031_MAX_WIDTH;
        a->bounds.height                = MT9T031_MAX_HEIGHT;
        a->defrect                      = a->bounds;
        a->type                         = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        a->pixelaspect.numerator        = 1;
        a->pixelaspect.denominator      = 1;

        return 0;
}

static int mt9t031_g_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        struct v4l2_pix_format *pix = &f->fmt.pix;

        pix->width              = mt9t031->rect.width / mt9t031->xskip;
        pix->height             = mt9t031->rect.height / mt9t031->yskip;
        pix->pixelformat        = V4L2_PIX_FMT_SGRBG10;
        pix->field              = V4L2_FIELD_NONE;
        pix->colorspace         = V4L2_COLORSPACE_SRGB;

        return 0;
}

static int mt9t031_s_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        struct soc_camera_device *icd = client->dev.platform_data;
        struct v4l2_pix_format *pix = &f->fmt.pix;
        u16 xskip, yskip;
        struct v4l2_rect rect = mt9t031->rect;

        /*
         * try_fmt has put width and height within limits.
         * S_FMT: use binning and skipping for scaling
         */
        xskip = mt9t031_skip(&rect.width, pix->width, MT9T031_MAX_WIDTH);
        yskip = mt9t031_skip(&rect.height, pix->height, MT9T031_MAX_HEIGHT);

        /* mt9t031_set_params() doesn't change width and height */
        return mt9t031_set_params(icd, &rect, xskip, yskip);
}

/*
 * If a user window larger than sensor window is requested, we'll increase the
 * sensor window.
 */
static int mt9t031_try_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
{
        struct v4l2_pix_format *pix = &f->fmt.pix;

        v4l_bound_align_image(
                &pix->width, MT9T031_MIN_WIDTH, MT9T031_MAX_WIDTH, 1,
                &pix->height, MT9T031_MIN_HEIGHT, MT9T031_MAX_HEIGHT, 1, 0);

        return 0;
}

static int mt9t031_g_chip_ident(struct v4l2_subdev *sd,
                                struct v4l2_dbg_chip_ident *id)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);

        if (id->match.type != V4L2_CHIP_MATCH_I2C_ADDR)
                return -EINVAL;

        if (id->match.addr != client->addr)
                return -ENODEV;

        id->ident       = mt9t031->model;
        id->revision    = 0;

        return 0;
}

#ifdef CONFIG_VIDEO_ADV_DEBUG
static int mt9t031_g_register(struct v4l2_subdev *sd,
                              struct v4l2_dbg_register *reg)
{
        struct i2c_client *client = sd->priv;

        if (reg->match.type != V4L2_CHIP_MATCH_I2C_ADDR || reg->reg > 0xff)
                return -EINVAL;

        if (reg->match.addr != client->addr)
                return -ENODEV;

        reg->val = reg_read(client, reg->reg);

        if (reg->val > 0xffff)
                return -EIO;

        return 0;
}

static int mt9t031_s_register(struct v4l2_subdev *sd,
                              struct v4l2_dbg_register *reg)
{
        struct i2c_client *client = sd->priv;

        if (reg->match.type != V4L2_CHIP_MATCH_I2C_ADDR || reg->reg > 0xff)
                return -EINVAL;

        if (reg->match.addr != client->addr)
                return -ENODEV;

        if (reg_write(client, reg->reg, reg->val) < 0)
                return -EIO;

        return 0;
}
#endif

static const struct v4l2_queryctrl mt9t031_controls[] = {
        {
                .id             = V4L2_CID_VFLIP,
                .type           = V4L2_CTRL_TYPE_BOOLEAN,
                .name           = "Flip Vertically",
                .minimum        = 0,
                .maximum        = 1,
                .step           = 1,
                .default_value  = 0,
        }, {
                .id             = V4L2_CID_HFLIP,
                .type           = V4L2_CTRL_TYPE_BOOLEAN,
                .name           = "Flip Horizontally",
                .minimum        = 0,
                .maximum        = 1,
                .step           = 1,
                .default_value  = 0,
        }, {
                .id             = V4L2_CID_GAIN,
                .type           = V4L2_CTRL_TYPE_INTEGER,
                .name           = "Gain",
                .minimum        = 0,
                .maximum        = 127,
                .step           = 1,
                .default_value  = 64,
                .flags          = V4L2_CTRL_FLAG_SLIDER,
        }, {
                .id             = V4L2_CID_EXPOSURE,
                .type           = V4L2_CTRL_TYPE_INTEGER,
                .name           = "Exposure",
                .minimum        = 1,
                .maximum        = 255,
                .step           = 1,
                .default_value  = 255,
                .flags          = V4L2_CTRL_FLAG_SLIDER,
        }, {
                .id             = V4L2_CID_EXPOSURE_AUTO,
                .type           = V4L2_CTRL_TYPE_BOOLEAN,
                .name           = "Automatic Exposure",
                .minimum        = 0,
                .maximum        = 1,
                .step           = 1,
                .default_value  = 1,
        }
};

static struct soc_camera_ops mt9t031_ops = {
        .set_bus_param          = mt9t031_set_bus_param,
        .query_bus_param        = mt9t031_query_bus_param,
        .controls               = mt9t031_controls,
        .num_controls           = ARRAY_SIZE(mt9t031_controls),
};

static int mt9t031_g_ctrl(struct v4l2_subdev *sd, struct v4l2_control *ctrl)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        int data;

        switch (ctrl->id) {
        case V4L2_CID_VFLIP:
                data = reg_read(client, MT9T031_READ_MODE_2);
                if (data < 0)
                        return -EIO;
                ctrl->value = !!(data & 0x8000);
                break;
        case V4L2_CID_HFLIP:
                data = reg_read(client, MT9T031_READ_MODE_2);
                if (data < 0)
                        return -EIO;
                ctrl->value = !!(data & 0x4000);
                break;
        case V4L2_CID_EXPOSURE_AUTO:
                ctrl->value = mt9t031->autoexposure;
                break;
        case V4L2_CID_GAIN:
                ctrl->value = mt9t031->gain;
                break;
        case V4L2_CID_EXPOSURE:
                ctrl->value = mt9t031->exposure;
                break;
        }
        return 0;
}

static int mt9t031_s_ctrl(struct v4l2_subdev *sd, struct v4l2_control *ctrl)
{
        struct i2c_client *client = sd->priv;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        struct soc_camera_device *icd = client->dev.platform_data;
        const struct v4l2_queryctrl *qctrl;
        int data;

        qctrl = soc_camera_find_qctrl(&mt9t031_ops, ctrl->id);

        if (!qctrl)
                return -EINVAL;

        switch (ctrl->id) {
        case V4L2_CID_VFLIP:
                if (ctrl->value)
                        data = reg_set(client, MT9T031_READ_MODE_2, 0x8000);
                else
                        data = reg_clear(client, MT9T031_READ_MODE_2, 0x8000);
                if (data < 0)
                        return -EIO;
                break;
        case V4L2_CID_HFLIP:
                if (ctrl->value)
                        data = reg_set(client, MT9T031_READ_MODE_2, 0x4000);
                else
                        data = reg_clear(client, MT9T031_READ_MODE_2, 0x4000);
                if (data < 0)
                        return -EIO;
                break;
        case V4L2_CID_GAIN:
                if (ctrl->value > qctrl->maximum || ctrl->value < qctrl->minimum)
                        return -EINVAL;
                /* See Datasheet Table 7, Gain settings. */
                if (ctrl->value <= qctrl->default_value) {
                        /* Pack it into 0..1 step 0.125, register values 0..8 */
                        unsigned long range = qctrl->default_value - qctrl->minimum;
                        data = ((ctrl->value - qctrl->minimum) * 8 + range / 2) / range;

                        dev_dbg(&client->dev, "Setting gain %d\n", data);
                        data = reg_write(client, MT9T031_GLOBAL_GAIN, data);
                        if (data < 0)
                                return -EIO;
                } else {
                        /* Pack it into 1.125..128 variable step, register values 9..0x7860 */
                        /* We assume qctrl->maximum - qctrl->default_value - 1 > 0 */
                        unsigned long range = qctrl->maximum - qctrl->default_value - 1;
                        /* calculated gain: map 65..127 to 9..1024 step 0.125 */
                        unsigned long gain = ((ctrl->value - qctrl->default_value - 1) *
                                               1015 + range / 2) / range + 9;

                        if (gain <= 32)         /* calculated gain 9..32 -> 9..32 */
                                data = gain;
                        else if (gain <= 64)    /* calculated gain 33..64 -> 0x51..0x60 */
                                data = ((gain - 32) * 16 + 16) / 32 + 80;
                        else
                                /* calculated gain 65..1024 -> (1..120) << 8 + 0x60 */
                                data = (((gain - 64 + 7) * 32) & 0xff00) | 0x60;

                        dev_dbg(&client->dev, "Set gain from 0x%x to 0x%x\n",
                                reg_read(client, MT9T031_GLOBAL_GAIN), data);
                        data = reg_write(client, MT9T031_GLOBAL_GAIN, data);
                        if (data < 0)
                                return -EIO;
                }

                /* Success */
                mt9t031->gain = ctrl->value;
                break;
        case V4L2_CID_EXPOSURE:
                /* mt9t031 has maximum == default */
                if (ctrl->value > qctrl->maximum || ctrl->value < qctrl->minimum)
                        return -EINVAL;
                else {
                        const unsigned long range = qctrl->maximum - qctrl->minimum;
                        const u32 shutter = ((ctrl->value - qctrl->minimum) * 1048 +
                                             range / 2) / range + 1;
                        u32 old;

                        get_shutter(client, &old);
                        dev_dbg(&client->dev, "Set shutter from %u to %u\n",
                                old, shutter);
                        if (set_shutter(client, shutter) < 0)
                                return -EIO;
                        mt9t031->exposure = ctrl->value;
                        mt9t031->autoexposure = 0;
                }
                break;
        case V4L2_CID_EXPOSURE_AUTO:
                if (ctrl->value) {
                        const u16 vblank = MT9T031_VERTICAL_BLANK;
                        const u32 shutter_max = MT9T031_MAX_HEIGHT + vblank;
                        unsigned int total_h = mt9t031->rect.height +
                                icd->y_skip_top + vblank;

                        if (set_shutter(client, total_h) < 0)
                                return -EIO;
                        qctrl = soc_camera_find_qctrl(icd->ops, V4L2_CID_EXPOSURE);
                        mt9t031->exposure = (shutter_max / 2 + (total_h - 1) *
                                 (qctrl->maximum - qctrl->minimum)) /
                                shutter_max + qctrl->minimum;
                        mt9t031->autoexposure = 1;
                } else
                        mt9t031->autoexposure = 0;
                break;
        }
        return 0;
}

/* Interface active, can use i2c. If it fails, it can indeed mean, that
 * this wasn't our capture interface, so, we wait for the right one */
static int mt9t031_video_probe(struct i2c_client *client)
{
        struct soc_camera_device *icd = client->dev.platform_data;
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        s32 data;
        int ret;

        /* Enable the chip */
        data = reg_write(client, MT9T031_CHIP_ENABLE, 1);
        dev_dbg(&client->dev, "write: %d\n", data);

        /* Read out the chip version register */
        data = reg_read(client, MT9T031_CHIP_VERSION);

        switch (data) {
        case 0x1621:
                mt9t031->model = V4L2_IDENT_MT9T031;
                icd->formats = mt9t031_colour_formats;
                icd->num_formats = ARRAY_SIZE(mt9t031_colour_formats);
                break;
        default:
                dev_err(&client->dev,
                        "No MT9T031 chip detected, register read %x\n", data);
                return -ENODEV;
        }

        dev_info(&client->dev, "Detected a MT9T031 chip ID %x\n", data);

        ret = mt9t031_idle(client);
        if (ret < 0)
                dev_err(&client->dev, "Failed to initialise the camera\n");

        /* mt9t031_idle() has reset the chip to default. */
        mt9t031->exposure = 255;
        mt9t031->gain = 64;

        return ret;
}

static struct v4l2_subdev_core_ops mt9t031_subdev_core_ops = {
        .g_ctrl         = mt9t031_g_ctrl,
        .s_ctrl         = mt9t031_s_ctrl,
        .g_chip_ident   = mt9t031_g_chip_ident,
#ifdef CONFIG_VIDEO_ADV_DEBUG
        .g_register     = mt9t031_g_register,
        .s_register     = mt9t031_s_register,
#endif
};

static struct v4l2_subdev_video_ops mt9t031_subdev_video_ops = {
        .s_stream       = mt9t031_s_stream,
        .s_fmt          = mt9t031_s_fmt,
        .g_fmt          = mt9t031_g_fmt,
        .try_fmt        = mt9t031_try_fmt,
        .s_crop         = mt9t031_s_crop,
        .g_crop         = mt9t031_g_crop,
        .cropcap        = mt9t031_cropcap,
};

static struct v4l2_subdev_ops mt9t031_subdev_ops = {
        .core   = &mt9t031_subdev_core_ops,
        .video  = &mt9t031_subdev_video_ops,
};

static int mt9t031_probe(struct i2c_client *client,
                         const struct i2c_device_id *did)
{
        struct mt9t031 *mt9t031;
        struct soc_camera_device *icd = client->dev.platform_data;
        struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
        struct soc_camera_link *icl;
        int ret;

        if (!icd) {
                dev_err(&client->dev, "MT9T031: missing soc-camera data!\n");
                return -EINVAL;
        }

        icl = to_soc_camera_link(icd);
        if (!icl) {
                dev_err(&client->dev, "MT9T031 driver needs platform data\n");
                return -EINVAL;
        }

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WORD_DATA)) {
                dev_warn(&adapter->dev,
                         "I2C-Adapter doesn't support I2C_FUNC_SMBUS_WORD\n");
                return -EIO;
        }

        mt9t031 = kzalloc(sizeof(struct mt9t031), GFP_KERNEL);
        if (!mt9t031)
                return -ENOMEM;

        v4l2_i2c_subdev_init(&mt9t031->subdev, client, &mt9t031_subdev_ops);

        /* Second stage probe - when a capture adapter is there */
        icd->ops                = &mt9t031_ops;
        icd->y_skip_top         = 0;

        mt9t031->rect.left      = MT9T031_COLUMN_SKIP;
        mt9t031->rect.top       = MT9T031_ROW_SKIP;
        mt9t031->rect.width     = MT9T031_MAX_WIDTH;
        mt9t031->rect.height    = MT9T031_MAX_HEIGHT;

        /* Simulated autoexposure. If enabled, we calculate shutter width
         * ourselves in the driver based on vertical blanking and frame width */
        mt9t031->autoexposure = 1;

        mt9t031->xskip = 1;
        mt9t031->yskip = 1;

        mt9t031_idle(client);

        ret = mt9t031_video_probe(client);

        mt9t031_disable(client);

        if (ret) {
                icd->ops = NULL;
                i2c_set_clientdata(client, NULL);
                kfree(mt9t031);
        }

        return ret;
}

static int mt9t031_remove(struct i2c_client *client)
{
        struct mt9t031 *mt9t031 = to_mt9t031(client);
        struct soc_camera_device *icd = client->dev.platform_data;

        icd->ops = NULL;
        i2c_set_clientdata(client, NULL);
        client->driver = NULL;
        kfree(mt9t031);

        return 0;
}

static const struct i2c_device_id mt9t031_id[] = {
        { "mt9t031", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, mt9t031_id);

static struct i2c_driver mt9t031_i2c_driver = {
        .driver = {
                .name = "mt9t031",
        },
        .probe          = mt9t031_probe,
        .remove         = mt9t031_remove,
        .id_table       = mt9t031_id,
};

static int __init mt9t031_mod_init(void)
{
        return i2c_add_driver(&mt9t031_i2c_driver);
}

static void __exit mt9t031_mod_exit(void)
{
        i2c_del_driver(&mt9t031_i2c_driver);
}

module_init(mt9t031_mod_init);
module_exit(mt9t031_mod_exit);

MODULE_DESCRIPTION("Micron MT9T031 Camera driver");
MODULE_AUTHOR("Guennadi Liakhovetski <lg@denx.de>");
MODULE_LICENSE("GPL v2");