uvc_isight.c

  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}