Re: Future handling of complex RGB devices on Linux v2

Gregor Riepl
2024-02-22T11:38:12Z

> This certainly is the most KISS approach. This proposal
> in essence is just an arbitrary command multiplexer /
> demultiplexer and ioctls already are exactly that.
>
> With the added advantage of being able to directly use
> pass the vendor-cmd-specific struct to the ioctl instead
> of having to first embed it in some other struct.

There's also the question of how much complexity needs to remain in the
kernel, if vendor-specific ioctls are made available.

Does every vendor driver implement a complex mapping to hardware
registers? What about drivers that basically implement no mapping at all
and simply forward all data to the hardware without any checking? The
latter case would match Pavel's concerns, although I don't see how this
is any different from the situation today, where userspace talks
directly to the hardware via libusb etc.

To be honest, I think the kernel shouldn't include too much high-level
complexity. If there is a desire to implement a generic display device
on top of the RGB device, this should be a configurable service running
in user space. The kernel should provide an interface to expose this
emulated display as a "real" display to applications - unless this can
also be done entirely in user space in a generic way.