1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  *	uvc_video.c  --  USB Video Class Gadget driver
4  *
5  *	Copyright (C) 2009-2010
6  *	    Laurent Pinchart (laurent.pinchart@ideasonboard.com)
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/device.h>
11 #include <linux/errno.h>
12 #include <linux/usb/ch9.h>
13 #include <linux/usb/gadget.h>
14 #include <linux/usb/video.h>
15 
16 #include <media/v4l2-dev.h>
17 
18 #include "uvc.h"
19 #include "uvc_queue.h"
20 #include "uvc_video.h"
21 
22 /* --------------------------------------------------------------------------
23  * Video codecs
24  */
25 
26 static int
27 uvc_video_encode_header(struct uvc_video *video, struct uvc_buffer *buf,
28 		u8 *data, int len)
29 {
30 	data[0] = 2;
31 	data[1] = UVC_STREAM_EOH | video->fid;
32 
33 	if (buf->bytesused - video->queue.buf_used <= len - 2)
34 		data[1] |= UVC_STREAM_EOF;
35 
36 	return 2;
37 }
38 
39 static int
40 uvc_video_encode_data(struct uvc_video *video, struct uvc_buffer *buf,
41 		u8 *data, int len)
42 {
43 	struct uvc_video_queue *queue = &video->queue;
44 	unsigned int nbytes;
45 	void *mem;
46 
47 	/* Copy video data to the USB buffer. */
48 	mem = buf->mem + queue->buf_used;
49 	nbytes = min((unsigned int)len, buf->bytesused - queue->buf_used);
50 
51 	memcpy(data, mem, nbytes);
52 	queue->buf_used += nbytes;
53 
54 	return nbytes;
55 }
56 
57 static void
58 uvc_video_encode_bulk(struct usb_request *req, struct uvc_video *video,
59 		struct uvc_buffer *buf)
60 {
61 	void *mem = req->buf;
62 	int len = video->req_size;
63 	int ret;
64 
65 	/* Add a header at the beginning of the payload. */
66 	if (video->payload_size == 0) {
67 		ret = uvc_video_encode_header(video, buf, mem, len);
68 		video->payload_size += ret;
69 		mem += ret;
70 		len -= ret;
71 	}
72 
73 	/* Process video data. */
74 	len = min((int)(video->max_payload_size - video->payload_size), len);
75 	ret = uvc_video_encode_data(video, buf, mem, len);
76 
77 	video->payload_size += ret;
78 	len -= ret;
79 
80 	req->length = video->req_size - len;
81 	req->zero = video->payload_size == video->max_payload_size;
82 
83 	if (buf->bytesused == video->queue.buf_used) {
84 		video->queue.buf_used = 0;
85 		buf->state = UVC_BUF_STATE_DONE;
86 		uvcg_queue_next_buffer(&video->queue, buf);
87 		video->fid ^= UVC_STREAM_FID;
88 
89 		video->payload_size = 0;
90 	}
91 
92 	if (video->payload_size == video->max_payload_size ||
93 	    buf->bytesused == video->queue.buf_used)
94 		video->payload_size = 0;
95 }
96 
97 static void
98 uvc_video_encode_isoc(struct usb_request *req, struct uvc_video *video,
99 		struct uvc_buffer *buf)
100 {
101 	void *mem = req->buf;
102 	int len = video->req_size;
103 	int ret;
104 
105 	/* Add the header. */
106 	ret = uvc_video_encode_header(video, buf, mem, len);
107 	mem += ret;
108 	len -= ret;
109 
110 	/* Process video data. */
111 	ret = uvc_video_encode_data(video, buf, mem, len);
112 	len -= ret;
113 
114 	req->length = video->req_size - len;
115 
116 	if (buf->bytesused == video->queue.buf_used) {
117 		video->queue.buf_used = 0;
118 		buf->state = UVC_BUF_STATE_DONE;
119 		uvcg_queue_next_buffer(&video->queue, buf);
120 		video->fid ^= UVC_STREAM_FID;
121 	}
122 }
123 
124 /* --------------------------------------------------------------------------
125  * Request handling
126  */
127 
128 static int uvcg_video_ep_queue(struct uvc_video *video, struct usb_request *req)
129 {
130 	int ret;
131 
132 	ret = usb_ep_queue(video->ep, req, GFP_ATOMIC);
133 	if (ret < 0) {
134 		uvcg_err(&video->uvc->func, "Failed to queue request (%d).\n",
135 			 ret);
136 
137 		/* Isochronous endpoints can't be halted. */
138 		if (usb_endpoint_xfer_bulk(video->ep->desc))
139 			usb_ep_set_halt(video->ep);
140 	}
141 
142 	return ret;
143 }
144 
145 /*
146  * I somehow feel that synchronisation won't be easy to achieve here. We have
147  * three events that control USB requests submission:
148  *
149  * - USB request completion: the completion handler will resubmit the request
150  *   if a video buffer is available.
151  *
152  * - USB interface setting selection: in response to a SET_INTERFACE request,
153  *   the handler will start streaming if a video buffer is available and if
154  *   video is not currently streaming.
155  *
156  * - V4L2 buffer queueing: the driver will start streaming if video is not
157  *   currently streaming.
158  *
159  * Race conditions between those 3 events might lead to deadlocks or other
160  * nasty side effects.
161  *
162  * The "video currently streaming" condition can't be detected by the irqqueue
163  * being empty, as a request can still be in flight. A separate "queue paused"
164  * flag is thus needed.
165  *
166  * The paused flag will be set when we try to retrieve the irqqueue head if the
167  * queue is empty, and cleared when we queue a buffer.
168  *
169  * The USB request completion handler will get the buffer at the irqqueue head
170  * under protection of the queue spinlock. If the queue is empty, the streaming
171  * paused flag will be set. Right after releasing the spinlock a userspace
172  * application can queue a buffer. The flag will then cleared, and the ioctl
173  * handler will restart the video stream.
174  */
175 static void
176 uvc_video_complete(struct usb_ep *ep, struct usb_request *req)
177 {
178 	struct uvc_video *video = req->context;
179 	struct uvc_video_queue *queue = &video->queue;
180 	struct uvc_buffer *buf;
181 	unsigned long flags;
182 	int ret;
183 
184 	switch (req->status) {
185 	case 0:
186 		break;
187 
188 	case -ESHUTDOWN:	/* disconnect from host. */
189 		uvcg_dbg(&video->uvc->func, "VS request cancelled.\n");
190 		uvcg_queue_cancel(queue, 1);
191 		goto requeue;
192 
193 	default:
194 		uvcg_info(&video->uvc->func,
195 			  "VS request completed with status %d.\n",
196 			  req->status);
197 		uvcg_queue_cancel(queue, 0);
198 		goto requeue;
199 	}
200 
201 	spin_lock_irqsave(&video->queue.irqlock, flags);
202 	buf = uvcg_queue_head(&video->queue);
203 	if (buf == NULL) {
204 		spin_unlock_irqrestore(&video->queue.irqlock, flags);
205 		goto requeue;
206 	}
207 
208 	video->encode(req, video, buf);
209 
210 	ret = uvcg_video_ep_queue(video, req);
211 	spin_unlock_irqrestore(&video->queue.irqlock, flags);
212 
213 	if (ret < 0) {
214 		uvcg_queue_cancel(queue, 0);
215 		goto requeue;
216 	}
217 
218 	return;
219 
220 requeue:
221 	spin_lock_irqsave(&video->req_lock, flags);
222 	list_add_tail(&req->list, &video->req_free);
223 	spin_unlock_irqrestore(&video->req_lock, flags);
224 }
225 
226 static int
227 uvc_video_free_requests(struct uvc_video *video)
228 {
229 	unsigned int i;
230 
231 	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
232 		if (video->req[i]) {
233 			usb_ep_free_request(video->ep, video->req[i]);
234 			video->req[i] = NULL;
235 		}
236 
237 		if (video->req_buffer[i]) {
238 			kfree(video->req_buffer[i]);
239 			video->req_buffer[i] = NULL;
240 		}
241 	}
242 
243 	INIT_LIST_HEAD(&video->req_free);
244 	video->req_size = 0;
245 	return 0;
246 }
247 
248 static int
249 uvc_video_alloc_requests(struct uvc_video *video)
250 {
251 	unsigned int req_size;
252 	unsigned int i;
253 	int ret = -ENOMEM;
254 
255 	BUG_ON(video->req_size);
256 
257 	req_size = video->ep->maxpacket
258 		 * max_t(unsigned int, video->ep->maxburst, 1)
259 		 * (video->ep->mult);
260 
261 	for (i = 0; i < UVC_NUM_REQUESTS; ++i) {
262 		video->req_buffer[i] = kmalloc(req_size, GFP_KERNEL);
263 		if (video->req_buffer[i] == NULL)
264 			goto error;
265 
266 		video->req[i] = usb_ep_alloc_request(video->ep, GFP_KERNEL);
267 		if (video->req[i] == NULL)
268 			goto error;
269 
270 		video->req[i]->buf = video->req_buffer[i];
271 		video->req[i]->length = 0;
272 		video->req[i]->complete = uvc_video_complete;
273 		video->req[i]->context = video;
274 
275 		list_add_tail(&video->req[i]->list, &video->req_free);
276 	}
277 
278 	video->req_size = req_size;
279 
280 	return 0;
281 
282 error:
283 	uvc_video_free_requests(video);
284 	return ret;
285 }
286 
287 /* --------------------------------------------------------------------------
288  * Video streaming
289  */
290 
291 /*
292  * uvcg_video_pump - Pump video data into the USB requests
293  *
294  * This function fills the available USB requests (listed in req_free) with
295  * video data from the queued buffers.
296  */
297 int uvcg_video_pump(struct uvc_video *video)
298 {
299 	struct uvc_video_queue *queue = &video->queue;
300 	struct usb_request *req;
301 	struct uvc_buffer *buf;
302 	unsigned long flags;
303 	int ret;
304 
305 	/* FIXME TODO Race between uvcg_video_pump and requests completion
306 	 * handler ???
307 	 */
308 
309 	while (1) {
310 		/* Retrieve the first available USB request, protected by the
311 		 * request lock.
312 		 */
313 		spin_lock_irqsave(&video->req_lock, flags);
314 		if (list_empty(&video->req_free)) {
315 			spin_unlock_irqrestore(&video->req_lock, flags);
316 			return 0;
317 		}
318 		req = list_first_entry(&video->req_free, struct usb_request,
319 					list);
320 		list_del(&req->list);
321 		spin_unlock_irqrestore(&video->req_lock, flags);
322 
323 		/* Retrieve the first available video buffer and fill the
324 		 * request, protected by the video queue irqlock.
325 		 */
326 		spin_lock_irqsave(&queue->irqlock, flags);
327 		buf = uvcg_queue_head(queue);
328 		if (buf == NULL) {
329 			spin_unlock_irqrestore(&queue->irqlock, flags);
330 			break;
331 		}
332 
333 		video->encode(req, video, buf);
334 
335 		/* Queue the USB request */
336 		ret = uvcg_video_ep_queue(video, req);
337 		spin_unlock_irqrestore(&queue->irqlock, flags);
338 
339 		if (ret < 0) {
340 			uvcg_queue_cancel(queue, 0);
341 			break;
342 		}
343 	}
344 
345 	spin_lock_irqsave(&video->req_lock, flags);
346 	list_add_tail(&req->list, &video->req_free);
347 	spin_unlock_irqrestore(&video->req_lock, flags);
348 	return 0;
349 }
350 
351 /*
352  * Enable or disable the video stream.
353  */
354 int uvcg_video_enable(struct uvc_video *video, int enable)
355 {
356 	unsigned int i;
357 	int ret;
358 
359 	if (video->ep == NULL) {
360 		uvcg_info(&video->uvc->func,
361 			  "Video enable failed, device is uninitialized.\n");
362 		return -ENODEV;
363 	}
364 
365 	if (!enable) {
366 		for (i = 0; i < UVC_NUM_REQUESTS; ++i)
367 			if (video->req[i])
368 				usb_ep_dequeue(video->ep, video->req[i]);
369 
370 		uvc_video_free_requests(video);
371 		uvcg_queue_enable(&video->queue, 0);
372 		return 0;
373 	}
374 
375 	if ((ret = uvcg_queue_enable(&video->queue, 1)) < 0)
376 		return ret;
377 
378 	if ((ret = uvc_video_alloc_requests(video)) < 0)
379 		return ret;
380 
381 	if (video->max_payload_size) {
382 		video->encode = uvc_video_encode_bulk;
383 		video->payload_size = 0;
384 	} else
385 		video->encode = uvc_video_encode_isoc;
386 
387 	return uvcg_video_pump(video);
388 }
389 
390 /*
391  * Initialize the UVC video stream.
392  */
393 int uvcg_video_init(struct uvc_video *video, struct uvc_device *uvc)
394 {
395 	INIT_LIST_HEAD(&video->req_free);
396 	spin_lock_init(&video->req_lock);
397 
398 	video->uvc = uvc;
399 	video->fcc = V4L2_PIX_FMT_YUYV;
400 	video->bpp = 16;
401 	video->width = 320;
402 	video->height = 240;
403 	video->imagesize = 320 * 240 * 2;
404 
405 	/* Initialize the video buffers queue. */
406 	uvcg_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT,
407 			&video->mutex);
408 	return 0;
409 }
410 
411