On Mon, 25 Nov 2024 at 13:01, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > 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 ? I still have not wired it to ChromeOS. But I do not expect to have any issues. it is relative simple to go from vdev to evdev and the other way around # ls -la /sys/class/video4linux/video0/device/input/input*/ drwxr-xr-x. 3 root root 0 Nov 25 06:56 event11 # ls -la /sys/class/input/event11/device/device/video4linux/ drwxr-xr-x. 3 root root 0 Nov 25 06:56 video0 drwxr-xr-x. 3 root root 0 Nov 25 06:56 video1 > > <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 > > > -- Ricardo Ribalda
