On Wed, 21 Feb 2024 23:17:52 +0100 Pavel Machek <pavel@xxxxxx> wrote: > Hi! > > > so after more feedback from the OpenRGB maintainers I came up with an even > > more generic proposal: > > https://gitlab.com/CalcProgrammer1/OpenRGB/-/issues/3916#note_1753072869 > > > >evaluate-set-command ioctl taking: > > >{ > > > enum command /* one of supported_commands */ > > > union data > > > { > > > char raw[3072], > > > { > > > <input struct for command 0> > > > }, > > Yeah, so ... this is not a interface. This is a backdoor to pass > arbitrary data. That's not going to fly. > > For keyboards, we don't need complete new interface; we reasonable > extensions over existing display APIs -- keyboards are clearly 2D. I suppose they could be seen as *a* display, but if you are referring to DRM KMS UAPI, then no, I don't see that fitting at all: - the "pixel grid" is not orthogonal, it's not a rectangle, and it might not be a grid at all - Timings and video modes? DRM KMS has always been somewhat awkward for display devices that do not have an inherent scanout cycle and timings totally depend on the amount of pixels updated at a time (FB_DAMAGE_CLIPS), e.g. USB displays (not USB-C DP alt mode). They do work, but they are very different from the usual hardware involved with KMS, require special consideration in userspace, and they still are actual displays while what we're talking about here are not. - KMS has no concept of programmed autonomous animations, and likely never will. They are not useful with actual displays. - Userspace will try to light up KMS outputs automatically and extend the traditional desktop there. This was already a problem for head-mounted displays (HMD) where it made no sense. That was worked around with an in-kernel list of HMDs and some KMS property quirking. Modern KMS UAPI very much aims to be a generic UAPI that abstracts display devices. It already breaks down a little for things like USB displays and virtual machines (e.g. qemu, vmware, especially with remote viewers), which I find unfortunate. With HMDs the genericity breaks down in other ways, but I'd claim HMDs are a better fit still than full-featured VM virtual displays (cursor plane hijacking). With non-displays like keyboards the genericity would be completely lost, as they won't work at all the same way as displays. You cannot even show proper images there, only coarse light patterns *IF* you actually know the pixel layout. But the pixel layout is(?) hardware-specific which is the opposite of generic. While you could dress keyboard lights etc. up with DRM KMS UAPI, the userspace would have to be written from scratch for them, and you somehow need to make existing KMS userspace to never touch those devices. What's the point of using DRM KMS UAPI in the first place, then? Thanks, pq
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