Hi, On 19-Dec-24 5:18 PM, Ricardo Ribalda wrote: > On Thu, 19 Dec 2024 at 17:05, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >> >> Hi, >> >> On 19-Dec-24 4:53 PM, Ricardo Ribalda wrote: >>> On Thu, 19 Dec 2024 at 16:41, Laurent Pinchart >>> <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: >>>> >>>> On Thu, Dec 19, 2024 at 04:35:37PM +0100, Ricardo Ribalda wrote: >>>>> On Thu, 19 Dec 2024 at 15:41, Laurent Pinchart wrote: >>>>>> On Thu, Dec 19, 2024 at 09:17:31AM +0100, Ricardo Ribalda wrote: >>>>>>> On Thu, 19 Dec 2024 at 00:27, Laurent Pinchart wrote: >>>>>>>> On Fri, Dec 13, 2024 at 11:21:02AM +0000, Ricardo Ribalda wrote: >>>>>>>>> To implement VIDIOC_QUERYCTRL, we need to read from the hardware all the >>>>>>>>> values that were not cached previously. If that read fails, we used to >>>>>>>>> report back the error to the user. >>>>>>>>> >>>>>>>>> Unfortunately this does not play nice with userspace. When they are >>>>>>>>> enumerating the contols, the only expect an error when there are no >>>>>>>>> "next" control. >>>>>>>>> >>>>>>>>> This is probably a corner case, and could be handled in userspace, but >>>>>>>>> both v4l2-ctl and yavta fail to enumerate all the controls if we return >>>>>>>>> then -EIO during VIDIOC_QUERYCTRL. I suspect that there are tons of >>>>>>>>> userspace apps handling this wrongly as well. >>>>>>>>> >>>>>>>>> This patch get around this issue by ignoring the hardware errors and >>>>>>>>> always returning 0 if a control exists. >>>>>>>>> >>>>>>>>> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> >>>>>>>>> --- >>>>>>>>> Hi 2*Hans and Laurent! >>>>>>>>> >>>>>>>>> I came around a device that was listing just a couple of controls when >>>>>>>>> it should be listing much more. >>>>>>>>> >>>>>>>>> Some debugging latter I found that the device was returning -EIO when >>>>>>>>> all the focal controls were read. >>>>>>>> >>>>>>>> Was it transient and random errors, or does the device always fail for >>>>>>>> those controls ? >>>>>>> >>>>>>> For one of the devices the control is always failing (or I could not >>>>>>> find a combination that made it work). >>>>>>> >>>>>>> For the other it was more or less random. >>>>>> >>>>>> Are there other controls that failed for that device ? And what >>>>>> request(s) fail, is it only GET_CUR or also GET_MIN/GET_MAX/GET_RES ? >>>>> >>>>> It is a mix. >>>>> >>>>>> What's the approximate frequency of those random failures ? >>>>>> >>>>>>>>> This could be solved in userspace.. but I suspect that a lot of people >>>>>>>>> has copied the implementation of v4l-utils or yavta. >>>>>>>>> >>>>>>>>> What do you think of this workaround? >>>>>>>> >>>>>>>> Pretending that the control could be queried is problematic. We'll >>>>>>>> return invalid values to the user, I don't think that's a good idea. If >>>>>>>> the problematic device always returns error for focus controls, we could >>>>>>>> add a quirk, and extend the uvc_device_info structure to list the >>>>>>>> controls to ignore. >>>>>>>> >>>>>>>> Another option would be to skip over controls that return -EIO within >>>>>>>> the kernel, and mark those controls are broken. I think this could be >>>>>>>> done transparently for userspace, the first time we try to populate the >>>>>>>> cache for such controls, a -EIO error would mark the control as broken, >>>>>>>> and from a userspace point of view it wouldn't be visible through as >>>>>>>> ioctl. >>>>>>> >>>>>>> I see a couple of issues with this: >>>>>>> - There are controls that fail randomly. >>>>>>> - There are controls that fail based on the value of other controls >>>>>>> (yeah, I know). >>>>>> >>>>>> I was fearing there would be random (or random-looking) failures, as >>>>>> that can preclude marking the controls as broken and fully hiding them >>>>>> from userspace :-( >>>>>> >>>>>>> - There are controls that do not implement RES, MIN, or MAX, but >>>>>>> besides that, they are completely functional. >>>>>>> In any of those cases we do not want to skip those controls. >>>>>>> >>>>>>> I am not against quirking specific cameras once we detect that they >>>>>>> are broken... >>>>>> >>>>>> Hopefully there won't be too many of those, right ? Righhhht... ? >>>>> >>>>> So far I have identified 4 in a week, and I am not testing obscure >>>>> camera modules.... >>>> >>>> Can you provide more information about those modules ? USB descriptors >>>> maybe, and the list of controls that fail, and how they fail ? >>> >>> These are the ones I can share now: >>> >>> "13d3:5519": Focus value out of range >>> focus_absolute 0x009a090a (int) : min=355 max=790 step=1 default=6 >>> value=500 flags=inactive >> >> Hmm this one looks like min and default are swapped ? >> >> So I guess this one needs a quirk which checks if default < min >> and in that case swaps them (the check is to avoid swapping >> with fixed fw). If these are built into chromebooks how about >> doing a fwupdate for the camera instead ? > > We do fwupdate whenever possible. But some modules are not updateable. > They either: lack DFU, or the flash is read-only, or the update > process has a non acceptable fail rate. Ok, I was just wondering if we could avoid having to add a quirk for this model. > We aim to detect compliance errors early in the development process. > V4L2-compliance now (almost) works with the uvcvideo driver. And that > helps a lot :) > > I plan to add quirks for the cameras that I can test. But we still > need a solution for all the external cameras and modules that are not > in the lab. I agree we need some solution for this, especially the broken controls hiding others is a problem which needs some workaround. I'm not sure what that workaround should look like though. Just returning 0 as your v2 patch does seems less then ideal. Lets continue discussing this after the Christmas break. Regards, Hans >>> "3277:0003": Focus returns -EIO >>> Focus Absolute and Focus, Automatic Continuous: return -EIO for at >>> least one of get_ max/min/res >>> >>> "0408:302f": Error reading AutoExposure Flags >>> UVC_GET_INFO returns invalid flags >> >> Regards, >> >> Hans >> >> >> > >
