Documentation/admin-guide/media/cec.rst

Source file repositories/reference/linux-study-clean/Documentation/admin-guide/media/cec.rst

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Documentation/admin-guide/media/cec.rst
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Support Tooling And Documentation
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Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GPL-2.0

========
HDMI CEC
========

Supported hardware in mainline
==============================

HDMI Transmitters:

- Exynos4
- Exynos5
- STIH4xx HDMI CEC
- V4L2 adv7511 (same HW, but a different driver from the drm adv7511)
- stm32
- Allwinner A10 (sun4i)
- Raspberry Pi
- dw-hdmi (Synopsis IP)
- amlogic (meson ao-cec and ao-cec-g12a)
- drm adv7511/adv7533
- omap4
- tegra
- rk3288, rk3399
- tda998x
- DisplayPort CEC-Tunneling-over-AUX on i915, nouveau and amdgpu
- ChromeOS EC CEC
- CEC for SECO boards (UDOO x86).
- Chrontel CH7322


HDMI Receivers:

- adv7604/11/12
- adv7842
- tc358743

USB Dongles (see below for additional information on how to use these
dongles):

- Pulse-Eight: the pulse8-cec driver implements the following module option:
  ``persistent_config``: by default this is off, but when set to 1 the driver
  will store the current settings to the device's internal eeprom and restore
  it the next time the device is connected to the USB port.

- RainShadow Tech. Note: this driver does not support the persistent_config
  module option of the Pulse-Eight driver. The hardware supports it, but I
  have no plans to add this feature. But I accept patches :-)

- Extron DA HD 4K PLUS HDMI Distribution Amplifier. See
  :ref:`extron_da_hd_4k_plus` for more information.

Miscellaneous:

- vivid: emulates a CEC receiver and CEC transmitter.
  Can be used to test CEC applications without actual CEC hardware.

- cec-gpio. If the CEC pin is hooked up to a GPIO pin then
  you can control the CEC line through this driver. This supports error
  injection as well.

- cec-gpio and Allwinner A10 (or any other driver that uses the CEC pin
  framework to drive the CEC pin directly): the CEC pin framework uses
  high-resolution timers. These timers are affected by NTP daemons that
  speed up or slow down the clock to sync with the official time. The
  chronyd server will by default increase or decrease the clock by
  1/12th. This will cause the CEC timings to go out of spec. To fix this,
  add a 'maxslewrate 40000' line to chronyd.conf. This limits the clock
  frequency change to 1/25th, which keeps the CEC timings within spec.

Annotation

Implementation Notes