Re: Does USB isochronous mode work on EHCI port?

["Frank Schäfer" <fschaefer.oss-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>]

Am 04.01.2013 14:20, schrieb Roger Quadros:
> Hi Gary,
>
> On 01/04/2013 02:20 PM, Gary Thomas wrote:
>>
>> On Thursday, January 3, 2013 9:21:19 AM UTC-7, Felipe Balbi wrote:
>>
>>     Hi,
>>
>>     On Wednesday, January 2, 2013 10:44:50 PM UTC+2, Gary Thomas wrote:
>>
>>         I have a video adapter attached to my EHCI port which runs full
>>         speed (480Mb/s) isochronous mode.  Sadly, I never get any data
>>         from the device (it uses the EM28xx driver).
>>         This same device + driver works fine on my laptop and from what
>>         I can tell looking at the module debug, it's failing when
>>         waiting for the ISOC frame data to arrive.
>>
>>         Should this work?  I recall lots of discussion in the past about
>>         ISOC transfers not working on certain OMAP devices...
>>
>>
>>     which kernel are you using ? Have you tested mainline kernel ?
>>
>>
>> I'm using the TI/Ubuntu kernel ( ti-ubuntu-3.4.0-1489.17)
>>
>> Using the mainline would be hard as there is a lot in this kernel that
>> isn't in the mainline.

I have added support for USB bulk transfers to the em28xx driver
recently. It will be include in kernels 3.9+.
Maybe it can be used to work around hardware problems with ISOC transfers.

So if your device has bulk endpoints for video (see lsusb -v), it's
probably worth testing the latest code from the media tree
(http://git.linuxtv.org/media_tree.git).
You will have to load the module with parameter usb_xfer_mode=1,
otherwise the driver selects ISOC transfers for TV devices by default.

Regards,
Frank
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