Messages in this thread | | | Date | Tue, 18 Oct 2022 17:28:19 +0200 | From | Michael Grzeschik <> | Subject | Re: [PATCH v3 6/6] usb: gadget: uvc: add configfs option for sg support |
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Hi Dan!
On Tue, Oct 18, 2022 at 10:14:54AM -0500, Dan Vacura wrote: >On Tue, Oct 18, 2022 at 10:32:33AM -0400, Alan Stern wrote: >> On Tue, Oct 18, 2022 at 02:27:13PM +0100, Dan Scally wrote: >> > On 17/10/2022 21:54, Dan Vacura wrote: >> > > The scatter gather support doesn't appear to work well with some UDC hw. >> > > Add the ability to turn on the feature depending on the controller in >> > > use. >> > > >> > > Signed-off-by: Dan Vacura <w36195@motorola.com> >> > >> > >> > Nitpick: I would call it use_sg everywhere, but either way: >> > >> > >> > Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com> >> > >> > Tested-by: Daniel Scally <dan.scally@ideasonboard.com> >> > >> > > --- >> > > V1 -> V2: >> > > - no change, new patch in serie >> > > V2 -> V3: >> > > - default on, same as baseline >> > > >> > > Documentation/ABI/testing/configfs-usb-gadget-uvc | 1 + >> > > Documentation/usb/gadget-testing.rst | 2 ++ >> > > drivers/usb/gadget/function/f_uvc.c | 2 ++ >> > > drivers/usb/gadget/function/u_uvc.h | 1 + >> > > drivers/usb/gadget/function/uvc_configfs.c | 2 ++ >> > > drivers/usb/gadget/function/uvc_queue.c | 4 ++-- >> > > 6 files changed, 10 insertions(+), 2 deletions(-) >> > > >> > > diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc >> > > index 5dfaa3f7f6a4..839a75fc28ee 100644 >> > > --- a/Documentation/ABI/testing/configfs-usb-gadget-uvc >> > > +++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc >> > > @@ -9,6 +9,7 @@ Description: UVC function directory >> > > streaming_interval 1..16 >> > > function_name string [32] >> > > req_int_skip_div unsigned int >> > > + sg_supported 0..1 >> > > =================== ============================= >> > > What: /config/usb-gadget/gadget/functions/uvc.name/control >> > > diff --git a/Documentation/usb/gadget-testing.rst b/Documentation/usb/gadget-testing.rst >> > > index f9b5a09be1f4..8e3072d6a590 100644 >> > > --- a/Documentation/usb/gadget-testing.rst >> > > +++ b/Documentation/usb/gadget-testing.rst >> > > @@ -796,6 +796,8 @@ The uvc function provides these attributes in its function directory: >> > > function_name name of the interface >> > > req_int_skip_div divisor of total requests to aid in calculating >> > > interrupt frequency, 0 indicates all interrupt >> > > + sg_supported allow for scatter gather to be used if the UDC >> > > + hw supports it >> >> Why is a configuration option needed for this? Why not always use SG >> when the UDC supports it? Or at least, make the decision automatically >> (say, based on the amount of data to be transferred) with no need for >> any user input? > >Patches for a fix and to select to use SG depending on amount of data >are already submitted and under review. I agree, ideally we don't need >this patch, but there have been several regressions uncovered with >enabling this support and it takes time to root cause these issues. >
>In my specific environment, Android GKI 2.0, changes need to get >upstreamed first here before they're pulled into Android device >software.
In fact this is actually a good policy, but adding workarounds mainline to "hopefully" fix the real problems later are probably not what this policy is about. Hopefully!
Michael
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