[PATCH 0/7] media: uvcvideo: Implement the Privacy GPIO as a subdevice

[Ricardo Ribalda <ribalda@chromium.org>]

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
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         : Analog Video Decoder

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>
---
Ricardo Ribalda (6):
      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
      media: uvcvideo: Introduce UVC_QUIRK_PRIVACY_DURING_STREAM

Yunke Cao (1):
      media: uvcvideo: reimplement 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                 | 112 +------------
 drivers/media/usb/uvc/uvc_entity.c                 |  20 ++-
 drivers/media/usb/uvc/uvc_gpio.c                   | 178 +++++++++++++++++++++
 drivers/media/usb/uvc/uvc_video.c                  |   4 +
 drivers/media/usb/uvc/uvcvideo.h                   |  31 ++--
 drivers/media/v4l2-core/v4l2-async.c               |   3 +-
 include/uapi/linux/media.h                         |   1 +
 10 files changed, 242 insertions(+), 154 deletions(-)
---
base-commit: c7ccf3683ac9746b263b0502255f5ce47f64fe0a
change-id: 20241030-uvc-subdev-89f4467a00b5

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>