aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/media/video/uvc/uvc_isight.c
blob: 8510e7259e7639cdf30e343801fa38792dd619f0 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
/*
 *      uvc_isight.c  --  USB Video Class driver - iSight support
 *
 *	Copyright (C) 2006-2007
 *		Ivan N. Zlatev <contact@i-nz.net>
 *	Copyright (C) 2008-2009
 *		Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *
 *      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->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->length - buf->bytesused;
		mem = buf->mem + buf->bytesused;
		nbytes = min(len, maxlen);
		memcpy(mem, data, nbytes);
		buf->bytesused += nbytes;

		if (len > maxlen || buf->bytesused == 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_streaming *stream,
		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(&stream->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(&stream->queue,
							buf);
		} while (ret == -EAGAIN);
	}
}