Hi Ricardo, On 18-Nov-24 5:47 PM, Ricardo Ribalda wrote: > Hi Hans > > On Mon, 18 Nov 2024 at 16:43, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: >> >> Hi All, >> >> On 15-Nov-24 9:20 AM, Ricardo Ribalda wrote: >>> On Fri, 15 Nov 2024 at 00:06, Laurent Pinchart >>> <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: <snip> >>>> How do you handle cameras that suffer from >>>> UVC_QUIRK_PRIVACY_DURING_STREAM ? >>> >>> For those b) does not work. >> >> I already suspected as much, but it is good to have this >> confirmed. >> >> I'm afraid that from a userspace API pov cameras with a GPIO >> which only works when powered-on need to be treated the same as >> cameras which only have UVC_CT_PRIVACY_CONTROL IOW in this case >> keep exporting V4L2_CID_PRIVACY instead of switching to evdev >> with SW_CAMERA_LENS_COVER. >> >> Unfortunately this will make the GPIO handling code in the UVC >> driver somewhat more involved since now we have both uAPI-s for >> GPIOs depending on UVC_QUIRK_PRIVACY_DURING_STREAM. >> >> But I think that this makes sense, this way we end up offering >> 2 uAPIs depending on the hw capabilities: >> >> 1. evdev with SW_CAMERA_LENS_COVER which always reports a reliable >> state + events on the state changing without needing to power-up >> the camera. >> >> 2. V4L2_CID_PRIVACY for the case where the camera needs to be >> powered-on (/dev/video opened) and where the ctrl possibly needs >> to be polled. >> >> Assuming we can all agree on this split based on hw capabilities >> I think that we must document this somewhere in the media subsystem >> documentation. We can then also write down there that >> SW_CAMERA_LENS_COVER only applies to internal cameras. > > I do not think that it is worth it to keep UVC_CT_PRIVACY_CONTROL for > the two devices that have connected the GPIO's pull up to the wrong > power rail. > Now that the GPIO can be used from userspace, I expect that those > errors will be found early in the design process and never reach > production stage. > > > If we use UVC_CT_PRIVACY_CONTROL for thes two devices: > - userspace will have to implement two different APIs > - the driver will have to duplicate the code. > - all that code will be very difficult to test: there are only 2 > devices affected and it requires manual intervention to properly test > it. > > I think that UVC_QUIRK_PRIVACY_DURING_STREAM is a good compromise and > the main user handles it properly. Ok, as you wish. Lets go with using SW_CAMERA_LENS_COVER for the 2 models with UVC_QUIRK_PRIVACY_DURING_STREAM too. <snip> >>>> Is there any ACPI- or WMI-provided information that could assist with >>>> associating a privacy GPIO with a camera ? I just realized I did not answer this question from Laurent in my previous reply. No unfortunately there is no ACPI- or WMI-provided information that could assist with associating ACPI/WMI camera privacy controls with a specific camera. Note that these are typically not exposed as a GPIO, but rather as some vendor firmware interface. Thinking more about this I'm starting to believe more and more that the privacy-control stuff should be handled by libcamera and then specifically by the pipeline-handler, with some helper code to share functionality where possible. E.g. on IPU6 equipped Windows laptops there may be some ACPI/WMI driver which provides a /dev/input/event# SW_CAMERA_LENS_COVER node. So I would expect the IPU6 pipeline-handler to search for such a /dev/input/event# node and then expose that to users of the camera through a to-be-defined API (I'm thinking a read-only control). The code to find the event node can be shared, because this would e.g. likely also apply to some IPU3 designs as well as upcoming IPU7 designs. <snip> >>>> We could include the evdev in the MC graph. That will of course only be >>>> possible if the kernel knows about that association in the first place. >>>> At least the 1st category of devices would benefit from this. >> >> Yes I was thinking about adding a link to the MC graph for this too. >> >> Ricardo I notice that in this v3 series you still create a v4l2-subdev >> for the GPIO handling and then add an ancillary link for the GPIO subdev >> to the mc-graph. But I'm not sure how that is helpful. Userspace would >> still need to do parent matching, but then match the evdev parent to >> the subdev after getting the subdev from the mc. In that case it might >> as well look at the physical (USB-interface) parent of the MC/video >> node and do parent matching on that avoiding the need to go through >> the MC at all. >> >> I think using the MC could still be useful by adding a new type of >> ancillary link to the MC API which provides a file-path as info to >> userspace rather then a mc-link and then just directly provide >> the /dev/input/event# path through this new API? >> >> I guess that extending the MC API like this might be a bit of >> a discussion. But it would already make sense to have this for >> the existing input device for the snapshot button. > > The driver creates a v4l2-subdevice for every entity, and the gpio > today is modeled as an entity. Ok I see that explains why the subdevice is there, thank you. > The patchset just adds an ancillary link as Sakari suggested. > I am not against removing the gpio entity all together if it is not needed. Right unlike other entities which are really part of the UVC specification, the GPIO is not a "real" UVC entity. So I wonder if, after switching to SW_CAMERA_LENS_COVER, having this as a v4l2-subdevice buys us anything ? If not I think removing it might be a good idea. As for the ancillary link, that was useful to have when the API was a v4l2-ctrl on the subdevice. Just like I doubt if having the subdevice at all gives us any added value, I also doubt if having the ancillary link gives us any added value. > Now that we are brainstorming here... what about adding a control that > contains the name of the input device (eventX)? Is that a horrible > idea? I don't know, my initial reaction is that does not feel right to me. >>>>>> We can specify >>>>>> that SW_CAMERA_LENS_COVER only applies to device internal >>>>>> cameras, but then it is up to userspace to determine which >>>>>> cameras that are. >>>>> >>>>> I am working on wiring up this to userspace right now.. I will report >>>>> back if it cannot do it. >> >> Ricardo, great, thank you! Ricardo, any status update on this ? <snip> >>>> Assuming the kernel could report the association between an evdev and >>>> camera, we would need to report which evdev SW_CAMERA_LENS_COVER >>>> originates from all the way from the evdev to the consumer of the event. >>>> How well is that supported in standard Linux system architectures ? If >>>> I'm not mistaken libinput will report the originating device, but how >>>> far up the stack is it propagated ? And which component would we expect >>>> to consume those events, should the camera evdev be managed by e.g. >>>> libcamera ? >> >> Good questions. Looking back at our 2 primary use-cases: >> >> a) Having an app which is using (trying to use) the camera show >> a notification to the user that the camera is turned-off by >> a privacy switch . >> >> b) Showing on on-screen-display (OSD) with a camera / >> crossed-out-camera icon when the switch is toggled, similar to how >> muting speakers/mic show an OSD . Laptop vendor Windows add-on >> software does this and I know that some users have been asking >> for this. >> >> I think we have everything to do b) in current compositors >> like gnome-shell. Using an evdev with SW_CAMERA_LENS_COVER >> would even be a lot easier for b) then the current >> V4L2_CID_PRIVACY API. >> >> a) though is a lot harder. We could open up access to >> the relevant /dev/input/event# node using a udev uaccess >> tag so that users who can access /dev/video# nodes also >> get raw access to that /dev/input/event# node and then >> libcamera could indeed provide this information that way. >> I think that is probably the best option. >> >> At least for the cases where the camera on/off switch >> does not simply make the camera completely disappear. >> >> That case is harder. atm that case is not handled at all >> though. So even just getting b) to work for that case >> would be nice / an improvement. >> >> Eventually if we give libcamera access to event# >> nodes which advertise SW_CAMERA_LENS_COVER (and no other >> privacy sensitive information) then libcamera could even >> separately offer some API for apps to just get that value >> if there is no camera to associate it with. >> >> Actually thinking more about it libcamera probably might >> be the right place for some sort of "no cameras found >> have you tried hitting your camera privacy-switch" API. >> That is some API to query if such a message should be >> shown to the user. But that is very much future work. > > Are standard apps expected to use libcamera directly or they should > use pipewire? > Maybe a) Should be pipewire's task? Standard apps are supposed to use pipewire, but IMHO this is really too low-level for pipewire to handle itself. Also see my remarks above about how I think this needs to be part of the pipeline handler. Since e.g. associating a /dev/input/event# SW_CAMERA_LENS_COVER node with a specific UVC camera is going to be UVC specific solution. For other pipeline-handlers combined with vendor fw-interfaces offering SW_CAMERA_LENS_COVER support I do not think that there is going to be a way to actually associate the 2. So we will likely simply have the pipeline handler for e.g. IPU6 simply associate any SW_CAMERA_LENS_COVER with the normal (non IR) user facing camera. Since we need this different ways to map a /dev/input/event# SW_CAMERA_LENS_COVER node to a specific camera this really needs to be done in libcamera IMHO. And I think this also solves the question about needing a kernel API to associate the /dev/input/event# with a specific /dev/video#. At least for now I think we don't need an API and instead we can simply walk sysfs to find the common USB-interface parent to associate the 2. See how xawtv associates the alsa and /dev/video# parts of tv-grabber cards for an example. Regards, Hans
