Re: [PATCH v2 0/6] media: uvcvideo: Implement the Privacy GPIO as a subdevice

Mauro Carvalho Chehab
2024-11-09T14:05:00Z

Em Fri, 08 Nov 2024 20:25:44 +0000
Ricardo Ribalda <ribalda@chromium.org> escreveu:

> 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....
>
> 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@chromium.org/
>
> 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

No matter if internally implemented as a subdevice or not,
UVC is not a MC-centric device[1].

It means that UVC can be compiled without media controller support,
and that its functionality shall be visible via /dev/video* nodes.

So, whatever internal implementation it is used, it shall not require
config MEDIA_CONTROLLER and the control shall be visible via
/dev/video*.

Moving privacy control out of /dev/video would mean that this will break
support for it on existing applications, which is a big nack. Now, it would
be acceptable to have this visible via V4L2 and subdev APIs.

[1] https://www.kernel.org/doc/html/latest/userspace-api/media/glossary.html#term-MC-centric

Regards,
Mauro

> 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@chromium.org>
> ---
> Changes in v2:
> - Rebase on top of https://patchwork.linuxtv.org/project/linux-media/patch/20241106-uvc-crashrmmod-v6-1-fbf9781c6e83@chromium.org/
> - 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@chromium.org
>
> ---
> 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
>
> Best regards,

Thanks,
Mauro