On Sat, Nov 09, 2024 at 04:37:10PM +0100, Hans de Goede wrote: > Hi Ricardo, > > FYI / some background: I have been asked to start helping / > co-maintaining UVC with Laurent. I'll send out a patch adding > myself as UVC maintainer soon. > > On 8-Nov-24 9:25 PM, Ricardo Ribalda wrote: > > Some notebooks have a button to disable the camera (not to be mistaken > > with the mechanical cover). This is a standard GPIO linked to the > > camera via the ACPI table. > > > > 4 years ago we added support for this button in UVC via the Privacy control. > > This has two issues: > > - If the camera has its own privacy control, it will be masked > > - We need to power-up the camera to read the privacy control gpio. > > > > We tried to fix the power-up issues implementing "granular power > > saving" but it has been more complicated than anticipated.... > > I have been discussing UVC power-management with Laurent, also > related to power-consumption issues caused by libcamera's pipeline > handler holding open the /dev/video# node as long as the camera > manager object exists. > > For now we have fixed this with some relatively small changes to > libcamera's uvcvideo pipeline handler, but that is really meant > as an interim solution and as this privacy control series shows > the power-management issues are real. > > Combined with Mauro's remarks about how this is an userspace ABI break (1) > I think we should maybe first take another look at the powermanagement > issues in general rather then moving forward with this series. > > My apologies for this, I realize how annoying it can be when you are > working on a patch series to fix a specific issue and a reviewer > moves the goal-posts like this. But I do really think that just fixing > the generic power-management issues would be better and I also think > that this should be feasible / not too hard. > > Here is what I have in mind for this: > > 1. Assume that the results of trying a specific fmt do not change over time. > > 2. Only allow userspace to request fmts which match one of the enum-fmts -> > enum-frame-sizes -> enum-frame-rates tripplet results > (constrain what userspace requests to these) > > 3. Run the equivalent of tryfmt on all possible combinations (so the usaul > 3 levels nested loop for this) on probe() and cache the results This is possibly problematic. If I recall correctly (it was a very long time ago), the gstreamer v4l2src element used to do this, and it resulted in very large delays (> 10s with some devices), and possibly in some devices crashing as well. > 4. Make try_fmt / set_fmt not poweron the device but instead constrain > the requested fmt to one from our cached fmts > > 5. On stream-on do the actual power-on + set-fmt + verify that we get > what we expect based on the cache, and otherwise return -EIO. > > I think that should sort the issue, assuming that 1. above holds true. > > One downside is that this stops UVC button presses from working when > not streaming. But userspace will typically only open the /dev/video# > node if it plans to stream anyways so there should not be much of > a difference wrt button press behavior. > > This should also make camera enumeration faster for apps, since > most apps / frameworks do the whole 3 levels nested loop for this > on startup, for which atm we go out to the hw, which now instead > will come from the fmts cache and thus will be much much faster, > so this should lead to a noticeable speedup for apps accessing UVC > cameras which would be another nice win. > > Downside is that the initial probe will take longer see we do > all the tryfmt-s there now. But I think that taking a bit longer > to probe while the machine is booting should not be an issue. It depends on how much "a bit" is. I don't think a >10s delay would be acceptable. > 1) Which is technically correct, but FWIW I agree with you that I think > most userspace consumers will not care > > > Last year, we proposed a patchset to implement the privacy gpio as a > > subdevice https://lore.kernel.org/linux-media/20230111-uvc_privacy_subdev-v1-0-f859ac9a01e3@xxxxxxxxxxxx/ > > > > I think it is a pretty clean solution and makes sense to use a > > subdevice for something that is a sub device of the camera :). > > > > This is an attempt to continue with that approach. > > > > Tested on gimble: > > gimble-rev3 ~ # v4l2-ctl --all -d /dev/v4l-subdev0 > > Driver Info: > > Driver version : 6.6.56 > > Capabilities : 0x00000000 > > Media Driver Info: > > Driver name : uvcvideo > > Model : HP 5M Camera: HP 5M Camera > > Serial : 0001 > > Bus info : usb-0000:00:14.0-6 > > Media version : 6.6.56 > > Hardware revision: 0x00009601 (38401) > > Driver version : 6.6.56 > > Interface Info: > > ID : 0x0300001d > > Type : V4L Sub-Device > > Entity Info: > > ID : 0x00000013 (19) > > Name : GPIO > > Function : Unknown sub-device (00020006) > > > > Camera Controls > > > > privacy 0x009a0910 (bool) : default=0 value=0 flags=read-only, volatile > > > > gimble-rev3 ~ # media-ctl -p > > Media controller API version 6.6.56 > > > > Media device information > > ------------------------ > > driver uvcvideo > > model HP 5M Camera: HP 5M Camera > > serial 0001 > > bus info usb-0000:00:14.0-6 > > hw revision 0x9601 > > driver version 6.6.56 > > > > Device topology > > - entity 1: HP 5M Camera: HP 5M Camera (1 pad, 1 link) > > type Node subtype V4L flags 1 > > device node name /dev/video0 > > pad0: Sink > > <- "Extension 8":1 [ENABLED,IMMUTABLE] > > > > - entity 4: HP 5M Camera: HP 5M Camera (0 pad, 0 link) > > type Node subtype V4L flags 0 > > device node name /dev/video1 > > > > - entity 8: Extension 8 (2 pads, 2 links, 0 routes) > > type V4L2 subdev subtype Unknown flags 0 > > pad0: Sink > > <- "Extension 4":1 [ENABLED,IMMUTABLE] > > pad1: Source > > -> "HP 5M Camera: HP 5M Camera":0 [ENABLED,IMMUTABLE] > > > > - entity 11: Extension 4 (2 pads, 2 links, 0 routes) > > type V4L2 subdev subtype Unknown flags 0 > > pad0: Sink > > <- "Processing 2":1 [ENABLED,IMMUTABLE] > > pad1: Source > > -> "Extension 8":0 [ENABLED,IMMUTABLE] > > > > - entity 14: Processing 2 (2 pads, 2 links, 0 routes) > > type V4L2 subdev subtype Unknown flags 0 > > pad0: Sink > > <- "Camera 1":0 [ENABLED,IMMUTABLE] > > pad1: Source > > -> "Extension 4":0 [ENABLED,IMMUTABLE] > > > > - entity 17: Camera 1 (1 pad, 1 link, 0 routes) > > type V4L2 subdev subtype Sensor flags 0 > > pad0: Source > > -> "Processing 2":0 [ENABLED,IMMUTABLE] > > > > - entity 19: GPIO (0 pad, 0 link, 0 routes) > > type V4L2 subdev subtype Decoder flags 0 > > device node name /dev/v4l-subdev0 > > > > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> > > --- > > Changes in v2: > > - Rebase on top of https://patchwork.linuxtv.org/project/linux-media/patch/20241106-uvc-crashrmmod-v6-1-fbf9781c6e83@xxxxxxxxxxxx/ > > - Create uvc_gpio_cleanup and uvc_gpio_deinit > > - Refactor quirk: do not disable irq > > - Change define number for MEDIA_ENT_F_GPIO > > - Link to v1: https://lore.kernel.org/r/20241031-uvc-subdev-v1-0-a68331cedd72@xxxxxxxxxxxx > > > > --- > > Ricardo Ribalda (5): > > media: uvcvideo: Factor out gpio functions to its own file > > Revert "media: uvcvideo: Allow entity-defined get_info and get_cur" > > media: uvcvideo: Create ancillary link for GPIO subdevice > > media: v4l2-core: Add new MEDIA_ENT_F_GPIO > > media: uvcvideo: Use MEDIA_ENT_F_GPIO for the GPIO entity > > > > Yunke Cao (1): > > media: uvcvideo: Re-implement privacy GPIO as a separate subdevice > > > > .../userspace-api/media/mediactl/media-types.rst | 4 + > > drivers/media/usb/uvc/Makefile | 3 +- > > drivers/media/usb/uvc/uvc_ctrl.c | 40 +---- > > drivers/media/usb/uvc/uvc_driver.c | 123 +------------- > > drivers/media/usb/uvc/uvc_entity.c | 20 ++- > > drivers/media/usb/uvc/uvc_gpio.c | 187 +++++++++++++++++++++ > > drivers/media/usb/uvc/uvc_video.c | 4 + > > drivers/media/usb/uvc/uvcvideo.h | 34 ++-- > > drivers/media/v4l2-core/v4l2-async.c | 3 +- > > include/uapi/linux/media.h | 1 + > > 10 files changed, 252 insertions(+), 167 deletions(-) > > --- > > base-commit: 4353256f5487e0c5c47e8ff764bf4f9e679fb525 > > change-id: 20241030-uvc-subdev-89f4467a00b5 -- Regards, Laurent Pinchart
