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 ? > "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
