drivers/media/usb/uvc/uvc_isight.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      uvc_isight.c  --  USB Video Class driver - iSight support
   4  *
   5  *      Copyright (C) 2006-2007
   6  *              Ivan N. Zlatev <contact@i-nz.net>
   7  *      Copyright (C) 2008-2009
   8  *              Laurent Pinchart <laurent.pinchart@ideasonboard.com>
   9  */
  10
  11 #include <linux/usb.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14
  15 #include "uvcvideo.h"
  16
  17 /*
  18  * Built-in iSight webcams implements most of UVC 1.0 except a
  19  * different packet format. Instead of sending a header at the
  20  * beginning of each isochronous transfer payload, the webcam sends a
  21  * single header per image (on its own in a packet), followed by
  22  * packets containing data only.
  23  *
  24  * Offset   Size (bytes)        Description
  25  * ------------------------------------------------------------------
  26  * 0x00 1       Header length
  27  * 0x01 1       Flags (UVC-compliant)
  28  * 0x02 4       Always equal to '11223344'
  29  * 0x06 8       Always equal to 'deadbeefdeadface'
  30  * 0x0e 16      Unknown
  31  *
  32  * The header can be prefixed by an optional, unknown-purpose byte.
  33  */
  34
  35 static int isight_decode(struct uvc_video_queue *queue, struct uvc_buffer *buf,
  36                 const u8 *data, unsigned int len)
  37 {
  38         static const u8 hdr[] = {
  39                 0x11, 0x22, 0x33, 0x44,
  40                 0xde, 0xad, 0xbe, 0xef,
  41                 0xde, 0xad, 0xfa, 0xce
  42         };
  43
  44         struct uvc_streaming *stream = uvc_queue_to_stream(queue);
  45         unsigned int maxlen, nbytes;
  46         u8 *mem;
  47         int is_header = 0;
  48
  49         if (buf == NULL)
  50                 return 0;
  51
  52         if ((len >= 14 && memcmp(&data[2], hdr, 12) == 0) ||
  53             (len >= 15 && memcmp(&data[3], hdr, 12) == 0)) {
  54                 uvc_dbg(stream->dev, FRAME, "iSight header found\n");
  55                 is_header = 1;
  56         }
  57
  58         /* Synchronize to the input stream by waiting for a header packet. */
  59         if (buf->state != UVC_BUF_STATE_ACTIVE) {
  60                 if (!is_header) {
  61                         uvc_dbg(stream->dev, FRAME,
  62                                 "Dropping packet (out of sync)\n");
  63                         return 0;
  64                 }
  65
  66                 buf->state = UVC_BUF_STATE_ACTIVE;
  67         }
  68
  69         /*
  70          * Mark the buffer as done if we're at the beginning of a new frame.
  71          *
  72          * Empty buffers (bytesused == 0) don't trigger end of frame detection
  73          * as it doesn't make sense to return an empty buffer.
  74          */
  75         if (is_header && buf->bytesused != 0) {
  76                 buf->state = UVC_BUF_STATE_DONE;
  77                 return -EAGAIN;
  78         }
  79
  80         /*
  81          * Copy the video data to the buffer. Skip header packets, as they
  82          * contain no data.
  83          */
  84         if (!is_header) {
  85                 maxlen = buf->length - buf->bytesused;
  86                 mem = buf->mem + buf->bytesused;
  87                 nbytes = min(len, maxlen);
  88                 memcpy(mem, data, nbytes);
  89                 buf->bytesused += nbytes;
  90
  91                 if (len > maxlen || buf->bytesused == buf->length) {
  92                         uvc_dbg(stream->dev, FRAME,
  93                                 "Frame complete (overflow)\n");
  94                         buf->state = UVC_BUF_STATE_DONE;
  95                 }
  96         }
  97
  98         return 0;
  99 }
 100
 101 void uvc_video_decode_isight(struct uvc_urb *uvc_urb, struct uvc_buffer *buf,
 102                         struct uvc_buffer *meta_buf)
 103 {
 104         struct urb *urb = uvc_urb->urb;
 105         struct uvc_streaming *stream = uvc_urb->stream;
 106         int ret, i;
 107
 108         for (i = 0; i < urb->number_of_packets; ++i) {
 109                 if (urb->iso_frame_desc[i].status < 0) {
 110                         uvc_dbg(stream->dev, FRAME,
 111                                 "USB isochronous frame lost (%d)\n",
 112                                 urb->iso_frame_desc[i].status);
 113                 }
 114
 115                 /*
 116                  * Decode the payload packet.
 117                  *
 118                  * uvc_video_decode is entered twice when a frame transition
 119                  * has been detected because the end of frame can only be
 120                  * reliably detected when the first packet of the new frame
 121                  * is processed. The first pass detects the transition and
 122                  * closes the previous frame's buffer, the second pass
 123                  * processes the data of the first payload of the new frame.
 124                  */
 125                 do {
 126                         ret = isight_decode(&stream->queue, buf,
 127                                         urb->transfer_buffer +
 128                                         urb->iso_frame_desc[i].offset,
 129                                         urb->iso_frame_desc[i].actual_length);
 130
 131                         if (buf == NULL)
 132                                 break;
 133
 134                         if (buf->state == UVC_BUF_STATE_DONE ||
 135                             buf->state == UVC_BUF_STATE_ERROR)
 136                                 buf = uvc_queue_next_buffer(&stream->queue,
 137                                                         buf);
 138                 } while (ret == -EAGAIN);
 139         }
 140 }