Hi Rahul, On Wed, Aug 20, 2025 at 04:46:52AM +0000, Rahul Rameshbabu wrote: > On Tue, 19 Aug, 2025 11:06:40 +0200 "Maxime Ripard" <mrip...@kernel.org> > wrote: > > Hi Rahul, > > > > On Mon, Aug 18, 2025 at 05:04:15AM +0000, Rahul Rameshbabu wrote: > >> I am working on a drm_connector scoped backlight API in Rust. I have been > >> looking through Hans de Goede's previous efforts on this topic to help > >> guide my design. My hope is to enable backlight control over external > >> displays through DDC or USB Monitor Control Class while also supporting > >> internal panels. In parallel, I would like to improve the driver > >> probing/selection mechanism when there are different candidates for driving > >> a backlight device. This initial RFC is mainly intended to sanity check > >> that the plumbing I have chosen for extending the DRM connector > >> functionality in Rust seems reasonable. > > > > It's a great goal, and I had that same discussion with Hans recently > > too, but I can't find the link between backling/DDC CI, and Rust. Can > > you elaborate? > > Hi Maxime, > > Sure, let me elaborate on this. You are right that plumbing DDC > CI/backlight support at the DRM connector level does not need to be > implemented in Rust. > > If we look at Hans's proposal, the suggested phase 2 was to add a > drm_connector helper function for plumbing a pointer to the backlight > device implementation. I had some model differences with regards to how > the API would look like, mostly stemming from concerns about providing > better runtime overriding of the acpi_video_get_backlight_type based > backlight selection. However, I am aligned with the direction of scoping > at the drm_connector level. I basically was interested in implementing > this helper functionality in Rust instead of C, which is where Rust came > into play. > > I was also interested in declaring and attaching a drm_property in Rust > for controlling properties such as backlight rather than updating the > drm_connector declaration in C as an experiment. > > Let me know if you feel like this work would be better off as a C > implementation. I can also send out a detailed architecture proposal to > the mailing list if that would help. > > Link: > https://lore.freedesktop.org/wayland-devel/0d188965-d809-81b5-74ce-7d30c49fe...@redhat.com/
Thanks for the explanation. I'm not sure Rust is at the point where we can use it for the framework. If we want to make this work useful, we have to make it consistent and usable across all drivers, but we do have drivers for architectures that aren't supported by Rust yet (let alone tier 1). So it feels to me that it would be a bit premature for that work to be in Rust. If you do want to use it from a Rust driver though, feel free to write bindings for it, that would be a great addition. Maxime
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