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
35static 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(p: &data[2], q: hdr, size: 12) == 0) ||
53 (len >= 15 && memcmp(p: &data[3], q: hdr, size: 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
101void 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(queue: &stream->queue, buf,
127 data: urb->transfer_buffer +
128 urb->iso_frame_desc[i].offset,
129 len: 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(queue: &stream->queue,
137 buf);
138 } while (ret == -EAGAIN);
139 }
140}
141

source code of linux/drivers/media/usb/uvc/uvc_isight.c