On Sun, 2020-01-26 at 23:01 -0500, Sanford Rockowitz wrote: > I'm unaware of plans to support DDC in the Linux kernel. I just discovered the ddcci-driver-linux project. It is available in Debian in the ddcci-dkms binary package. I've tried it locally but it doesn't appear to be very useful for me yet. https://gitlab.com/ddcci-driver-linux/ddcci-driver-linux > a Qt based C++ GUI, ddcui I note that this isn't available in Debian yet, I am assuming that is why you have brought this discussion to the list. > On the other hand, there are things that ddcutil does to accommodate > variations in monitor DDC/CI implementations that probably don't > belong in the kernel. I think the Linux kernel already deals with quirks for various types of hardware, so I don't think it would be too much trouble to maintain the code for the DDC quirk types in the Linux kernel and the application of those quirks in udev. I think that this is typically how hardware quirks are applied on Linux based distributions. > Finally, unifying brightness control means alternatively using ACPI for > laptop displays and DDC for others. It seems to me that even if the > kernel supported DDC, this ACPI/DDC unification is more appropriately > done at a higher level than the kernel, probably in xrandr. For the > time being, an application can unify these facilities using libddcutil > for DDC. The Linux kernel already exposes LED information and control, display brightness and control and so on in standard ways, which are then consumed by userland tools, either directly or via daemons. So I think it isn't too much of a stretch for those to be available for DDC too. xrandr isn't used by Wayland based shells so that isn't the appropriate layer to introduce this feature. Keeping the DDC code out of the Linux kernel means that every single desktop has to add support for libddcutil instead of just adding it to Linux. Since Wayland shells run as the user rather than root, Wayland apps are not allowed to be run as root and accessing i2c devices on Linux typically requires root, control of monitor brightness via DDC won't be available for Wayland shells/apps, only via terminal or X11 applications run via sudo. > (The KDE-Neon folks currently use a private copy of libddcutil > for this purpose.) Any particular reason they can't use the official version? PS: are you aware of the ddccontrol project (also in Debian)? It has a monitor database, shared library, command-line tools and GUI. https://github.com/ddccontrol/ddccontrol https://github.com/ddccontrol/ddccontrol-db It would be great if yourself and the folks from ddcci-driver-linux and ddccontrol could work together in order to come up with a modern design and implementation for supporting control of monitors under Linux. -- bye, pabs https://wiki.debian.org/PaulWise
Attachment:
signature.asc
Description: This is a digitally signed message part