Linux 5.13 To Support HDMI CEC With The Raspberry Pi 4
Written by Michael Larabel in Hardware on 4 March 2021 at 09:03 AM EST. 5 Comments
HARDWARE --
While the 5.12 merge window hasn't even been closed for a full week yet, there is already the first DRM-Misc-Next pull request heading into DRM-Next with the first batch of feature material aiming for the Linux 5.13 kernel cycle.

This initial batch of DRM-Misc-Next includes the removal of TTM memory management and Medfield support from the GMA500 "Poulsbo" driver that goes along with the rest of the Linux kernel dropping the Intel MID support for 5.12 and lingering remnants being removed with 5.13. There is also i.MX8MM support added to the MSXFB driver among many other random changes to these smaller drivers.

Arguably most significant with this DRM-Misc-Next pull request is HDMI CEC support for the Raspberry Pi 4 / BCM2711 SoC with the VC4 DRM driver. CEC is the Consumer Electronics Control support for controlling HDMI-connected devices. HDMI CEC is also marketed under different technology names by the different vendors but ultimately is allowing for convenient control of connected devices.

Going back all the way to mid-2017 were early patches for HDMI CEC support with the VC4 driver to benefit the Raspberry Pi 4. Those patches ultimately were never mainlined and now in modern form there are these new patches on their way for mainline to support this HDMI feature on the Raspberry Pi 4 with the VC4 direct rendering manager driver.

This support is long overdue but in any case should be here with the 5.13 mainline kernel thanks to this drm-misc-next material for those wanting to use a Raspberry Pi 4 as a HTPC system or other multimedia use-cases where this feature can come in handy. The patches going to mainline for CEC with the BCM2711 were led by Maxime Ripard. (Previously the patches were just carried by the Raspberry Pi kernel builds and not the mainline Linux kernel tree.)

Those wanting to experiment with HDMI CEC support from Linux systems can use the cec-ctl command that is provided by the V4L utilities.
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