uvcvideo: uvc_scan_fallback() for webcams with broken chain (dc68ed0a) · Commits · e / devices / android_kernel_fairphone_FP3

drivers/media/usb/uvc/uvc_driver.c

+112 −6

Original line number	Diff line number	Diff line
		@@ -1595,6 +1595,114 @@ static const char uvc_print_chain(struct uvc_video_chain chain)
		return buffer;
		}

		static struct uvc_video_chain uvc_alloc_chain(struct uvc_device dev)
		{
		struct uvc_video_chain *chain;

		chain = kzalloc(sizeof(*chain), GFP_KERNEL);
		if (chain == NULL)
		return NULL;

		INIT_LIST_HEAD(&chain->entities);
		mutex_init(&chain->ctrl_mutex);
		chain->dev = dev;
		v4l2_prio_init(&chain->prio);

		return chain;
		}

		/*
		* Fallback heuristic for devices that don't connect units and terminals in a
		* valid chain.
		*
		* Some devices have invalid baSourceID references, causing uvc_scan_chain()
		* to fail, but if we just take the entities we can find and put them together
		* in the most sensible chain we can think of, turns out they do work anyway.
		* Note: This heuristic assumes there is a single chain.
		*
		* At the time of writing, devices known to have such a broken chain are
		* - Acer Integrated Camera (5986:055a)
		* - Realtek rtl157a7 (0bda:57a7)
		*/
		static int uvc_scan_fallback(struct uvc_device *dev)
		{
		struct uvc_video_chain *chain;
		struct uvc_entity *iterm = NULL;
		struct uvc_entity *oterm = NULL;
		struct uvc_entity *entity;
		struct uvc_entity *prev;

		/*
		* Start by locating the input and output terminals. We only support
		* devices with exactly one of each for now.
		*/
		list_for_each_entry(entity, &dev->entities, list) {
		if (UVC_ENTITY_IS_ITERM(entity)) {
		if (iterm)
		return -EINVAL;
		iterm = entity;
		}

		if (UVC_ENTITY_IS_OTERM(entity)) {
		if (oterm)
		return -EINVAL;
		oterm = entity;
		}
		}

		if (iterm == NULL \|\| oterm == NULL)
		return -EINVAL;

		/* Allocate the chain and fill it. */
		chain = uvc_alloc_chain(dev);
		if (chain == NULL)
		return -ENOMEM;

		if (uvc_scan_chain_entity(chain, oterm) < 0)
		goto error;

		prev = oterm;

		/*
		* Add all Processing and Extension Units with two pads. The order
		* doesn't matter much, use reverse list traversal to connect units in
		* UVC descriptor order as we build the chain from output to input. This
		* leads to units appearing in the order meant by the manufacturer for
		* the cameras known to require this heuristic.
		*/
		list_for_each_entry_reverse(entity, &dev->entities, list) {
		if (entity->type != UVC_VC_PROCESSING_UNIT &&
		entity->type != UVC_VC_EXTENSION_UNIT)
		continue;

		if (entity->num_pads != 2)
		continue;

		if (uvc_scan_chain_entity(chain, entity) < 0)
		goto error;

		prev->baSourceID[0] = entity->id;
		prev = entity;
		}

		if (uvc_scan_chain_entity(chain, iterm) < 0)
		goto error;

		prev->baSourceID[0] = iterm->id;

		list_add_tail(&chain->list, &dev->chains);

		uvc_trace(UVC_TRACE_PROBE,
		"Found a video chain by fallback heuristic (%s).\n",
		uvc_print_chain(chain));

		return 0;

		error:
		kfree(chain);
		return -EINVAL;
		}

		/*
		* Scan the device for video chains and register video devices.
		*
		@@ -1617,15 +1725,10 @@ static int uvc_scan_device(struct uvc_device *dev)
		if (term->chain.next \|\| term->chain.prev)
		continue;

		chain = kzalloc(sizeof(*chain), GFP_KERNEL);
		chain = uvc_alloc_chain(dev);
		if (chain == NULL)
		return -ENOMEM;

		INIT_LIST_HEAD(&chain->entities);
		mutex_init(&chain->ctrl_mutex);
		chain->dev = dev;
		v4l2_prio_init(&chain->prio);

		term->flags \|= UVC_ENTITY_FLAG_DEFAULT;

		if (uvc_scan_chain(chain, term) < 0) {
		@@ -1639,6 +1742,9 @@ static int uvc_scan_device(struct uvc_device *dev)
		list_add_tail(&chain->list, &dev->chains);
		}

		if (list_empty(&dev->chains))
		uvc_scan_fallback(dev);

		if (list_empty(&dev->chains)) {
		uvc_printk(KERN_INFO, "No valid video chain found.\n");
		return -1;