Re: [PATCH 3/3] media: uvcvideo: eUSB2 double isochronous bandwidth support

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 16.6.2025 12.43, Laurent Pinchart wrote:
> Hi Mathias,
> 
> Thank you for the patch.
> 
> On Mon, Jun 16, 2025 at 12:37:30PM +0300, Mathias Nyman wrote:
>> From: Tao Q Tao <tao.q.tao@intel.com>
>>
>> Add eUSB2 support to check total number of bytes, isochronous endpoint
>> will transfer every service interval(SI).
>>
>> Co-developed-by: Amardeep Rai <amardeep.rai@intel.com>
>> Signed-off-by: Amardeep Rai <amardeep.rai@intel.com>
>> Signed-off-by: Tao Q Tao <tao.q.tao@intel.com>
>> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
>> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
>> ---
>>   drivers/media/usb/uvc/uvc_video.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
>> index e3567aeb0007..a888f84208c6 100644
>> --- a/drivers/media/usb/uvc/uvc_video.c
>> +++ b/drivers/media/usb/uvc/uvc_video.c
>> @@ -1906,6 +1906,11 @@ u16 uvc_endpoint_max_bpi(struct usb_device *dev, struct usb_host_endpoint *ep)
>>   	case USB_SPEED_SUPER:
>>   	case USB_SPEED_SUPER_PLUS:
>>   		return le16_to_cpu(ep->ss_ep_comp.wBytesPerInterval);
>> +	case USB_SPEED_HIGH:
>> +		psize = usb_endpoint_maxp(&ep->desc);
>> +		if (psize == 0 && le16_to_cpu(dev->descriptor.bcdUSB) == 0x220)
>> +			return le32_to_cpu(ep->eusb2_isoc_ep_comp.dwBytesPerInterval);
>> +		fallthrough;
> 
> Instead of adding yet another case here, and eventually in a bunch of
> other drivers, could we centralize retrieval of the maximum bpi value in
> a helper function provided by the USB core ?

Sounds reasonable to me.
I'm not sure if any other drivers will need it as this feature seems to be made
specifically for integrated webcams, but things evolve.

Thanks
Mathias