media: uvcvideo: Implement the Privacy GPIO as a evdev

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 three 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.
- Other drivers have not followed this approach and have used evdev.

We tried to fix the power-up issues implementing "granular power
saving" but it has been more complicated than anticipated...

This patchset implements the Privacy GPIO as a evdev.

The first patch of this set is already in Laurent's tree... but I
include it to get some CI coverage.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
Changes in v4:
- Remove gpio entity, it is not needed.
- Use unit->gpio.irq in free_irq to make smatch happy.
- Link to v3: https://lore.kernel.org/r/20241112-uvc-subdev-v3-0-0ea573...

Changes in v3:
- CodeStyle (Thanks Sakari)
- Re-implement as input device
- Make the code depend on UVC_INPUT_EVDEV
- Link to v2: https://lore.kernel.org/r/20241108-uvc-subdev-v2-0-85d8a0...

Changes in v2:
- Rebase on top of https://patchwork.linuxtv.org/project/linux-media/patch/2...
- 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-a68331...

---
Ricardo Ribalda (7):
      media: uvcvideo: Fix crash during unbind if gpio unit is in use
      media: uvcvideo: Factor out gpio functions to its own file
      media: uvcvideo: Re-implement privacy GPIO as an input device
      Revert "media: uvcvideo: Allow entity-defined get_info and get_cur"
      media: uvcvideo: Introduce UVC_QUIRK_PRIVACY_DURING_STREAM
      media: uvcvideo: Make gpio_unit entity-less
      media: uvcvideo: Remove UVC_EXT_GPIO entity

 drivers/media/usb/uvc/Kconfig      |   2 +-
 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 |   7 +-
 drivers/media/usb/uvc/uvc_gpio.c   | 134 +++++++++++++++++++++++++++++++++++++
 drivers/media/usb/uvc/uvc_status.c |  13 +++-
 drivers/media/usb/uvc/uvc_video.c  |   4 ++
 drivers/media/usb/uvc/uvcvideo.h   |  43 +++++++-----
 9 files changed, 195 insertions(+), 174 deletions(-)
---
base-commit: 72ad4ff638047bbbdf3232178fea4bec1f429319
change-id: 20241030-uvc-subdev-89f4467a00b5

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