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[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: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Mauro Carvalho Chehab 2012-12-23 13:25:38 -02:00
parent a3efa1cc0e
commit 8b2aea7878
1 changed files with 25 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
drivers/media/usb/em28xx/em28xx-cards.c
View File

@ -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,