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

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Jun 16, 2025 at 04:05:54PM +0300, Mathias Nyman wrote:
> On 16.6.2025 12.43, Laurent Pinchart wrote:
> > 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.

Even if eUSB2 doesn't get used by other devices, I think centralizing
the whole max bpi calculation will be useful to handle the different
USB_SPEED_*.

-- 
Regards,

Laurent Pinchart