1/*
2 *      uvc_isight.c  --  USB Video Class driver - iSight support
3 *
4 *	Copyright (C) 2006-2007
5 *		Ivan N. Zlatev <contact@i-nz.net>
6 *	Copyright (C) 2008-2009
7 *		Laurent Pinchart <laurent.pinchart@ideasonboard.com>
8 *
9 *      This program is free software; you can redistribute it and/or modify
10 *      it under the terms of the GNU General Public License as published by
11 *      the Free Software Foundation; either version 2 of the License, or
12 *      (at your option) any later version.
13 *
14 */
15
16#include <linux/usb.h>
17#include <linux/kernel.h>
18#include <linux/mm.h>
19
20#include "uvcvideo.h"
21
22/* Built-in iSight webcams implements most of UVC 1.0 except a
23 * different packet format. Instead of sending a header at the
24 * beginning of each isochronous transfer payload, the webcam sends a
25 * single header per image (on its own in a packet), followed by
26 * packets containing data only.
27 *
28 * Offset   Size (bytes)	Description
29 * ------------------------------------------------------------------
30 * 0x00 	1   	Header length
31 * 0x01 	1   	Flags (UVC-compliant)
32 * 0x02 	4   	Always equal to '11223344'
33 * 0x06 	8   	Always equal to 'deadbeefdeadface'
34 * 0x0e 	16  	Unknown
35 *
36 * The header can be prefixed by an optional, unknown-purpose byte.
37 */
38
39static int isight_decode(struct uvc_video_queue *queue, struct uvc_buffer *buf,
40		const __u8 *data, unsigned int len)
41{
42	static const __u8 hdr[] = {
43		0x11, 0x22, 0x33, 0x44,
44		0xde, 0xad, 0xbe, 0xef,
45		0xde, 0xad, 0xfa, 0xce
46	};
47
48	unsigned int maxlen, nbytes;
49	__u8 *mem;
50	int is_header = 0;
51
52	if (buf == NULL)
53		return 0;
54
55	if ((len >= 14 && memcmp(&data[2], hdr, 12) == 0) ||
56	    (len >= 15 && memcmp(&data[3], hdr, 12) == 0)) {
57		uvc_trace(UVC_TRACE_FRAME, "iSight header found\n");
58		is_header = 1;
59	}
60
61	/* Synchronize to the input stream by waiting for a header packet. */
62	if (buf->state != UVC_BUF_STATE_ACTIVE) {
63		if (!is_header) {
64			uvc_trace(UVC_TRACE_FRAME, "Dropping packet (out of "
65				  "sync).\n");
66			return 0;
67		}
68
69		buf->state = UVC_BUF_STATE_ACTIVE;
70	}
71
72	/* Mark the buffer as done if we're at the beginning of a new frame.
73	 *
74	 * Empty buffers (bytesused == 0) don't trigger end of frame detection
75	 * as it doesn't make sense to return an empty buffer.
76	 */
77	if (is_header && buf->bytesused != 0) {
78		buf->state = UVC_BUF_STATE_DONE;
79		return -EAGAIN;
80	}
81
82	/* Copy the video data to the buffer. Skip header packets, as they
83	 * contain no data.
84	 */
85	if (!is_header) {
86		maxlen = buf->length - buf->bytesused;
87		mem = buf->mem + buf->bytesused;
88		nbytes = min(len, maxlen);
89		memcpy(mem, data, nbytes);
90		buf->bytesused += nbytes;
91
92		if (len > maxlen || buf->bytesused == buf->length) {
93			uvc_trace(UVC_TRACE_FRAME, "Frame complete "
94				  "(overflow).\n");
95			buf->state = UVC_BUF_STATE_DONE;
96		}
97	}
98
99	return 0;
100}
101
102void uvc_video_decode_isight(struct urb *urb, struct uvc_streaming *stream,
103		struct uvc_buffer *buf)
104{
105	int ret, i;
106
107	for (i = 0; i < urb->number_of_packets; ++i) {
108		if (urb->iso_frame_desc[i].status < 0) {
109			uvc_trace(UVC_TRACE_FRAME, "USB isochronous frame "
110				  "lost (%d).\n",
111				  urb->iso_frame_desc[i].status);
112		}
113
114		/* Decode the payload packet.
115		 * uvc_video_decode is entered twice when a frame transition
116		 * has been detected because the end of frame can only be
117		 * reliably detected when the first packet of the new frame
118		 * is processed. The first pass detects the transition and
119		 * closes the previous frame's buffer, the second pass
120		 * processes the data of the first payload of the new frame.
121		 */
122		do {
123			ret = isight_decode(&stream->queue, buf,
124					urb->transfer_buffer +
125					urb->iso_frame_desc[i].offset,
126					urb->iso_frame_desc[i].actual_length);
127
128			if (buf == NULL)
129				break;
130
131			if (buf->state == UVC_BUF_STATE_DONE ||
132			    buf->state == UVC_BUF_STATE_ERROR)
133				buf = uvc_queue_next_buffer(&stream->queue,
134							buf);
135		} while (ret == -EAGAIN);
136	}
137}
138