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Commit 8b2aea78 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[media] em28xx: prefer bulk mode on webcams 



Using bulk mode allows more than one webcam, as the maximum fps
is low at 640x480 resolution. So, prefer it, if the device is
a webcam.

Tested with Silvercrest 1.3 Mpixel webcam (em2710) on both bulk and isoc
modes.

Tested analog with HVR-950 model 65201/A1C0 (em2883), where only ISOC
endpoints are available for both DVB and Analog.

Tested on Hauppauge WinTV USB 2 (em2840) on both bulk and isoc modes.

It should be noticed that enabling bulk mode by default with TV boards
is a bad idea; what happens is that, while with ISOC the USB logic will
prevent the concurrent usage of two devices that spends more than 100%
of the USB2 traffic, it doesn't care with bulk transfers.

On my tests, I started two streams, one with a WinTV at 640x480x30fps
and the other one with a Silvercrest webcam at 640x480, on a lower fps)
both on bulk mode. One of the streams always silently failed.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent a3efa1cc

drivers/media/usb/em28xx/em28xx-cards.c

+25 −11
Original line number Diff line number Diff line
@@ -61,9 +61,9 @@ static unsigned int card[] = {[0 ... (EM28XX_MAXBOARDS - 1)] = UNSET }; 
module_param_array(card,  int, NULL, 0444);

MODULE_PARM_DESC(card,     "card type");



static unsigned int prefer_bulk;

static int prefer_bulk = -1;

module_param(prefer_bulk, int, 0444);

MODULE_PARM_DESC(prefer_bulk, "prefer USB bulk transfers");

MODULE_PARM_DESC(prefer_bulk, "prefer USB bulk transfers (-1 = auto, 0 = isoc, 1 = bulk)");





/* Bitmask marking allocated devices from 0 to EM28XX_MAXBOARDS - 1 */
@@ -3170,7 +3170,7 @@ static int em28xx_usb_probe(struct usb_interface *interface, 
	struct em28xx *dev = NULL;

	int retval;

	bool has_audio = false, has_video = false, has_dvb = false;

	int i, nr;

	int i, nr, try_bulk;

	const int ifnum = interface->altsetting[0].desc.bInterfaceNumber;

	char *speed;
@@ -3344,14 +3344,6 @@ static int em28xx_usb_probe(struct usb_interface *interface, 
		goto err_free;

	}



	/* Select USB transfer types to use */

	if (has_video &&

	    (!dev->analog_ep_isoc || (prefer_bulk && dev->analog_ep_bulk)))

		dev->analog_xfer_bulk = 1;

	if (has_dvb &&

	    (!dev->dvb_ep_isoc || (prefer_bulk && dev->dvb_ep_bulk)))

		dev->dvb_xfer_bulk = 1;



	dev->devno = nr;

	dev->model = id->driver_info;

	dev->alt   = -1;
@@ -3402,7 +3394,29 @@ static int em28xx_usb_probe(struct usb_interface *interface, 
		goto unlock_and_free;

	}



	if (prefer_bulk < 0) {

		if (dev->board.is_webcam)

			try_bulk = 1;

		else

			try_bulk = 0;

	} else {

		try_bulk = prefer_bulk > 0;

	}



	/* Select USB transfer types to use */

	if (has_video) {

	    if (!dev->analog_ep_isoc || (try_bulk && dev->analog_ep_bulk))

		dev->analog_xfer_bulk = 1;

		em28xx_info("analog set to %s mode.\n",

			    dev->analog_xfer_bulk ? "bulk" : "isoc");

	}

	if (has_dvb) {

	    if (!dev->dvb_ep_isoc || (try_bulk && dev->dvb_ep_bulk))

		dev->dvb_xfer_bulk = 1;



		em28xx_info("dvb set to %s mode.\n",

			    dev->dvb_xfer_bulk ? "bulk" : "isoc");



		/* pre-allocate DVB usb transfer buffers */

		if (dev->dvb_xfer_bulk) {

			retval = em28xx_alloc_urbs(dev, EM28XX_DIGITAL_MODE,