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(&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
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(&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}
141