/*
 * A driver for the Griffin Technology, Inc. "PowerMate" USB controller dial.
 *
 * v1.1, (c)2002 William R Sowerbutts <will@sowerbutts.com>
 *
 * This device is an anodized aluminium knob which connects over USB. It can measure
 * clockwise and anticlockwise rotation. The dial also acts as a pushbutton with
 * a spring for automatic release. The base contains a pair of LEDs which illuminate
 * the translucent base. It rotates without limit and reports its relative rotation
 * back to the host when polled by the USB controller.
 *
 * Testing with the knob I have has shown that it measures approximately 96 "clicks"
 * for one full rotation. Testing with my High Speed Rotation Actuator (ok, it was 
 * a variable speed cordless electric drill) has shown that the device can measure
 * speeds of up to 7 clicks either clockwise or anticlockwise between pollings from
 * the host. If it counts more than 7 clicks before it is polled, it will wrap back
 * to zero and start counting again. This was at quite high speed, however, almost
 * certainly faster than the human hand could turn it. Griffin say that it loses a
 * pulse or two on a direction change; the granularity is so fine that I never
 * noticed this in practice.
 *
 * The device's microcontroller can be programmed to set the LED to either a constant
 * intensity, or to a rhythmic pulsing. Several patterns and speeds are available.
 *
 * Griffin were very happy to provide documentation and free hardware for development.
 *
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/usb.h>

#define POWERMATE_VENDOR       0x077d    /* Griffin Technology, Inc. */
#define POWERMATE_PRODUCT_NEW  0x0410    /* Griffin PowerMate */
#define POWERMATE_PRODUCT_OLD  0x04AA    /* Griffin soundKnob */

/* these are the command codes we send to the device */
#define SET_STATIC_BRIGHTNESS  0x01
#define SET_PULSE_ASLEEP       0x02
#define SET_PULSE_AWAKE        0x03
#define SET_PULSE_MODE         0x04

/* these refer to bits in the powermate_device's requires_update field. */
#define UPDATE_STATIC_BRIGHTNESS (1<<0)
#define UPDATE_PULSE_ASLEEP      (1<<1)
#define UPDATE_PULSE_AWAKE       (1<<2)
#define UPDATE_PULSE_MODE        (1<<3)

/* at least two versions of the hardware exist, with differing payload 
   sizes. the first three bytes always contain the "interesting" data in
   the relevant format. */
#define POWERMATE_PAYLOAD_SIZE_MAX 6
#define POWERMATE_PAYLOAD_SIZE_MIN 3
struct powermate_device {
        signed char data[POWERMATE_PAYLOAD_SIZE_MAX];
        struct urb irq, config;
        struct usb_ctrlrequest configdr;
        struct usb_device *udev;
        struct input_dev input;
        struct semaphore lock;
        int static_brightness;
        int pulse_speed;
        int pulse_table;
        int pulse_asleep;
        int pulse_awake;
        int requires_update; // physical settings which are out of sync
        char phys[64];
};

static char pm_name_powermate[] = "Griffin PowerMate";
static char pm_name_soundknob[] = "Griffin SoundKnob";

static void powermate_config_complete(struct urb *urb); /* forward declararation of callback */

/* Callback for data arriving from the PowerMate over the USB interrupt pipe */
static void powermate_irq(struct urb *urb)
{
        struct powermate_device *pm = urb->context;

        if(urb->status)
                return;

        /* handle updates to device state */
        input_report_key(&pm->input, BTN_0, pm->data[0] & 0x01);
        input_report_rel(&pm->input, REL_DIAL, pm->data[1]);
}

/* Decide if we need to issue a control message and do so. Must be called with pm->lock down */
static void powermate_sync_state(struct powermate_device *pm)
{
        if(pm->requires_update == 0) 
                return; /* no updates are required */
        if(pm->config.status == -EINPROGRESS) 
                return; /* an update is already in progress; it'll issue this update when it completes */

        if(pm->requires_update & UPDATE_PULSE_ASLEEP){
                pm->configdr.wValue = cpu_to_le16( SET_PULSE_ASLEEP );
                pm->configdr.wIndex = cpu_to_le16( pm->pulse_asleep ? 1 : 0 );
                pm->requires_update &= ~UPDATE_PULSE_ASLEEP;
        }else if(pm->requires_update & UPDATE_PULSE_AWAKE){
                pm->configdr.wValue = cpu_to_le16( SET_PULSE_AWAKE );
                pm->configdr.wIndex = cpu_to_le16( pm->pulse_awake ? 1 : 0 );
                pm->requires_update &= ~UPDATE_PULSE_AWAKE;
        }else if(pm->requires_update & UPDATE_PULSE_MODE){
                int op, arg;
                /* the powermate takes an operation and an argument for its pulse algorithm.
                   the operation can be:
                   0: divide the speed
                   1: pulse at normal speed
                   2: multiply the speed
                   the argument only has an effect for operations 0 and 2, and ranges between
                   1 (least effect) to 255 (maximum effect).
       
                   thus, several states are equivalent and are coalesced into one state.

                   we map this onto a range from 0 to 510, with:
                   0 -- 254    -- use divide (0 = slowest)
                   255         -- use normal speed
                   256 -- 510  -- use multiple (510 = fastest).

                   Only values of 'arg' quite close to 255 are particularly useful/spectacular.
                */    
                if(pm->pulse_speed < 255){
                        op = 0;                   // divide
                        arg = 255 - pm->pulse_speed;
                }else if(pm->pulse_speed > 255){
                        op = 2;                   // multiply
                        arg = pm->pulse_speed - 255;
                }else{
                        op = 1;                   // normal speed
                        arg = 0;                  // can be any value
                }
                pm->configdr.wValue = cpu_to_le16( (pm->pulse_table << 8) | SET_PULSE_MODE );
                pm->configdr.wIndex = cpu_to_le16( (arg << 8) | op );
                pm->requires_update &= ~UPDATE_PULSE_MODE;
        }else if(pm->requires_update & UPDATE_STATIC_BRIGHTNESS){
                pm->configdr.wValue = cpu_to_le16( SET_STATIC_BRIGHTNESS );
                pm->configdr.wIndex = cpu_to_le16( pm->static_brightness );
                pm->requires_update &= ~UPDATE_STATIC_BRIGHTNESS;
        }else{
                printk(KERN_ERR "powermate: unknown update required");
                pm->requires_update = 0; /* fudge the bug */
                return;
        }

        pm->config.dev = pm->udev; /* is this necessary? */
        pm->configdr.bRequestType = 0x41; /* vendor request */
        pm->configdr.bRequest = 0x01;
        pm->configdr.wLength = 0;

        FILL_CONTROL_URB(&pm->config, pm->udev, usb_sndctrlpipe(pm->udev, 0), 
                         (void*)&pm->configdr, 0, 0, powermate_config_complete, pm);    

        if(usb_submit_urb(&pm->config))
                printk(KERN_ERR "powermate: usb_submit_urb(config) failed");
}

/* Called when our asynchronous control message completes. We may need to issue another immediately */
static void powermate_config_complete(struct urb *urb)
{
        struct powermate_device *pm = urb->context;

        if(urb->status)
                printk(KERN_ERR "powermate: config urb returned %d\n", urb->status);
        
        down(&pm->lock);
        powermate_sync_state(pm);
        up(&pm->lock);
}

/* Set the LED up as described and begin the sync with the hardware if required */
static void powermate_pulse_led(struct powermate_device *pm, int static_brightness, int pulse_speed, 
                                int pulse_table, int pulse_asleep, int pulse_awake)
{
        if(pulse_speed < 0)
                pulse_speed = 0;
        if(pulse_table < 0)
                pulse_table = 0;
        if(pulse_speed > 510)
                pulse_speed = 510;
        if(pulse_table > 2)
                pulse_table = 2;

        pulse_asleep = !!pulse_asleep;
        pulse_awake = !!pulse_awake;

        down(&pm->lock);

        /* mark state updates which are required */
        /* we update the static brightness if we've changed pulse mode,
           because the hardware seems to stick at an arbitrary value rather
           than jumping back to the static brightness we requested */
        if(static_brightness != pm->static_brightness){
                pm->static_brightness = static_brightness;
                pm->requires_update |= UPDATE_STATIC_BRIGHTNESS;                
        }
        if(pulse_asleep != pm->pulse_asleep){
                pm->pulse_asleep = pulse_asleep;
                pm->requires_update |= (UPDATE_PULSE_ASLEEP | UPDATE_STATIC_BRIGHTNESS);
        }
        if(pulse_awake != pm->pulse_awake){
                pm->pulse_awake = pulse_awake;
                pm->requires_update |= (UPDATE_PULSE_AWAKE | UPDATE_STATIC_BRIGHTNESS);
        }
        if(pulse_speed != pm->pulse_speed || pulse_table != pm->pulse_table){
                pm->pulse_speed = pulse_speed;
                pm->pulse_table = pulse_table;
                pm->requires_update |= UPDATE_PULSE_MODE;
        }

        powermate_sync_state(pm);
   
        up(&pm->lock);
}

/* Callback from the Input layer when an event arrives from userspace to configure the LED */
static int powermate_input_event(struct input_dev *dev, unsigned int type, unsigned int code, int _value)
{
        unsigned int command = (unsigned int)_value;
        struct powermate_device *pm = dev->private;

        if(type == EV_MSC && code == MSC_PULSELED){
                /*  
                    bits  0- 7: 8 bits: LED brightness
                    bits  8-16: 9 bits: pulsing speed modifier (0 ... 510); 0-254 = slower, 255 = standard, 256-510 = faster.
                    bits 17-18: 2 bits: pulse table (0, 1, 2 valid)
                    bit     19: 1 bit : pulse whilst asleep?
                    bit     20: 1 bit : pulse constantly?
                */  
                int static_brightness = command & 0xFF;   // bits 0-7
                int pulse_speed = (command >> 8) & 0x1FF; // bits 8-16
                int pulse_table = (command >> 17) & 0x3;  // bits 17-18
                int pulse_asleep = (command >> 19) & 0x1; // bit 19
                int pulse_awake  = (command >> 20) & 0x1; // bit 20
  
                powermate_pulse_led(pm, static_brightness, pulse_speed, pulse_table, pulse_asleep, pulse_awake);
        }

        return 0;
}

/* Called whenever a USB device matching one in our supported devices table is connected */
static void *powermate_probe(struct usb_device *udev, unsigned int ifnum, const struct usb_device_id *id)
{
        struct usb_interface_descriptor *interface;
        struct usb_endpoint_descriptor *endpoint;
        struct powermate_device *pm;
        int pipe, maxp;

        interface = udev->config[0].interface[ifnum].altsetting + 0;
        endpoint = interface->endpoint + 0;
        if (!(endpoint->bEndpointAddress & 0x80)) return NULL;
        if ((endpoint->bmAttributes & 3) != 3) return NULL;

        usb_set_protocol(udev, interface->bInterfaceNumber, 0);
        usb_set_idle(udev, interface->bInterfaceNumber, 0, 0);

        if (!(pm = kmalloc(sizeof(struct powermate_device), GFP_KERNEL)))
                return NULL;

        memset(pm, 0, sizeof(struct powermate_device));
        pm->udev = udev;

        init_MUTEX(&pm->lock);

        /* get a handle to the interrupt data pipe */
        pipe = usb_rcvintpipe(udev, endpoint->bEndpointAddress);
        maxp = usb_maxpacket(udev, pipe, usb_pipeout(pipe));

        if(maxp < POWERMATE_PAYLOAD_SIZE_MIN || maxp > POWERMATE_PAYLOAD_SIZE_MAX){
                printk("powermate: Expected payload of %d--%d bytes, found %d bytes!\n", 
                       POWERMATE_PAYLOAD_SIZE_MIN, POWERMATE_PAYLOAD_SIZE_MAX, maxp);
                maxp = POWERMATE_PAYLOAD_SIZE_MAX;
        }


        FILL_INT_URB(&pm->irq, udev, pipe, pm->data, maxp, powermate_irq, pm, endpoint->bInterval);

        /* register our interrupt URB with the USB system */
        if(usb_submit_urb(&pm->irq)) {
                kfree(pm);
                return NULL; /* failure */
        }

        switch (udev->descriptor.idProduct) {
        case POWERMATE_PRODUCT_NEW: pm->input.name = pm_name_powermate; break;
        case POWERMATE_PRODUCT_OLD: pm->input.name = pm_name_soundknob; break;
        default: 
          pm->input.name = pm_name_soundknob;
          printk(KERN_WARNING "powermate: unknown product id %04x\n", udev->descriptor.idProduct);
        }

        pm->input.private = pm;
        pm->input.evbit[0] = BIT(EV_KEY) | BIT(EV_REL) | BIT(EV_MSC);
        pm->input.keybit[LONG(BTN_0)] = BIT(BTN_0);
        pm->input.relbit[LONG(REL_DIAL)] = BIT(REL_DIAL);
        pm->input.mscbit[LONG(MSC_PULSELED)] = BIT(MSC_PULSELED);
        pm->input.idbus = BUS_USB;
        pm->input.idvendor = udev->descriptor.idVendor;
        pm->input.idproduct = udev->descriptor.idProduct;
        pm->input.idversion = udev->descriptor.bcdDevice;
        pm->input.event = powermate_input_event;

        input_register_device(&pm->input);

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 5, 0) /* Vojtech -- is this the correct version? */
        {
                char path[64];
                usb_make_path(udev, path, 64);
                snprintf(pm->phys, 64, "%s/input0", path);
                printk(KERN_INFO "input: %s on %s\n", pm->input.name, pm->input.path);
        }
#else
        printk(KERN_INFO "input: %s on input%d\n", pm->input.name, pm->input.number);
#endif
        
        /* force an update of everything */
        pm->requires_update = UPDATE_PULSE_ASLEEP | UPDATE_PULSE_AWAKE | UPDATE_PULSE_MODE | UPDATE_STATIC_BRIGHTNESS;
        powermate_pulse_led(pm, 0x80, 255, 0, 1, 0); // set default pulse parameters
  
        return pm;
}

/* Called when a USB device we've accepted ownership of is removed */
static void powermate_disconnect(struct usb_device *dev, void *ptr)
{
        struct powermate_device *pm = ptr;
        down(&pm->lock);
        pm->requires_update = 0;
        usb_unlink_urb(&pm->irq);  
        input_unregister_device(&pm->input);
  
        kfree(pm);
}

static struct usb_device_id powermate_devices [] = {
        { USB_DEVICE(POWERMATE_VENDOR, POWERMATE_PRODUCT_NEW) },
        { USB_DEVICE(POWERMATE_VENDOR, POWERMATE_PRODUCT_OLD) },
        { } /* Terminating entry */
};

MODULE_DEVICE_TABLE (usb, powermate_devices);

static struct usb_driver powermate_driver = {
        name:           "powermate",
        probe:          powermate_probe,
        disconnect:     powermate_disconnect,
        id_table:       powermate_devices,
};

int powermate_init(void)
{
        if (usb_register(&powermate_driver) < 0)
                return -1;
        return 0;
}

void powermate_cleanup(void)
{
        usb_deregister(&powermate_driver);
}

module_init(powermate_init);
module_exit(powermate_cleanup);

MODULE_AUTHOR( "William R Sowerbutts" );
MODULE_DESCRIPTION( "Griffin Technology, Inc PowerMate driver" );
MODULE_LICENSE("GPL");