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/*
* uvc_isight.c -- USB Video Class driver - iSight support
*
* Copyright (C) 2006-2007
* Ivan N. Zlatev <contact@i-nz.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
*/
#include <linux/usb.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include "uvcvideo.h"
/* Built-in iSight webcams implements most of UVC 1.0 except a
* different packet format. Instead of sending a header at the
* beginning of each isochronous transfer payload, the webcam sends a
* single header per image (on its own in a packet), followed by
* packets containing data only.
*
* Offset Size (bytes) Description
* ------------------------------------------------------------------
* 0x00 1 Header length
* 0x01 1 Flags (UVC-compliant)
* 0x02 4 Always equal to '11223344'
* 0x06 8 Always equal to 'deadbeefdeadface'
* 0x0e 16 Unknown
*
* The header can be prefixed by an optional, unknown-purpose byte.
*/
static int isight_decode(struct uvc_video_queue *queue, struct uvc_buffer *buf,
const __u8 *data, unsigned int len)
{
static const __u8 hdr[] = {
0x11, 0x22, 0x33, 0x44,
0xde, 0xad, 0xbe, 0xef,
0xde, 0xad, 0xfa, 0xce
};
unsigned int maxlen, nbytes;
__u8 *mem;
int is_header = 0;
if (buf == NULL)
return 0;
if ((len >= 14 && memcmp(&data[2], hdr, 12) == 0) ||
(len >= 15 && memcmp(&data[3], hdr, 12) == 0)) {
uvc_trace(UVC_TRACE_FRAME, "iSight header found\n");
is_header = 1;
}
/* Synchronize to the input stream by waiting for a header packet. */
if (buf->state != UVC_BUF_STATE_ACTIVE) {
if (!is_header) {
uvc_trace(UVC_TRACE_FRAME, "Dropping packet (out of "
"sync).\n");
return 0;
}
buf->state = UVC_BUF_STATE_ACTIVE;
}
/* Mark the buffer as done if we're at the beginning of a new frame.
*
* Empty buffers (bytesused == 0) don't trigger end of frame detection
* as it doesn't make sense to return an empty buffer.
*/
if (is_header && buf->buf.bytesused != 0) {
buf->state = UVC_BUF_STATE_DONE;
return -EAGAIN;
}
/* Copy the video data to the buffer. Skip header packets, as they
* contain no data.
*/
if (!is_header) {
maxlen = buf->buf.length - buf->buf.bytesused;
mem = queue->mem + buf->buf.m.offset + buf->buf.bytesused;
nbytes = min(len, maxlen);
memcpy(mem, data, nbytes);
buf->buf.bytesused += nbytes;
if (len > maxlen || buf->buf.bytesused == buf->buf.length) {
uvc_trace(UVC_TRACE_FRAME, "Frame complete "
"(overflow).\n");
buf->state = UVC_BUF_STATE_DONE;
}
}
return 0;
}
void uvc_video_decode_isight(struct urb *urb, struct uvc_video_device *video,
struct uvc_buffer *buf)
{
int ret, i;
for (i = 0; i < urb->number_of_packets; ++i) {
if (urb->iso_frame_desc[i].status < 0) {
uvc_trace(UVC_TRACE_FRAME, "USB isochronous frame "
"lost (%d).\n",
urb->iso_frame_desc[i].status);
}
/* Decode the payload packet.
* uvc_video_decode is entered twice when a frame transition
* has been detected because the end of frame can only be
* reliably detected when the first packet of the new frame
* is processed. The first pass detects the transition and
* closes the previous frame's buffer, the second pass
* processes the data of the first payload of the new frame.
*/
do {
ret = isight_decode(&video->queue, buf,
urb->transfer_buffer +
urb->iso_frame_desc[i].offset,
urb->iso_frame_desc[i].actual_length);
if (buf == NULL)
break;
if (buf->state == UVC_BUF_STATE_DONE ||
buf->state == UVC_BUF_STATE_ERROR)
buf = uvc_queue_next_buffer(&video->queue, buf);
} while (ret == -EAGAIN);
}
}
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