[v2,3/8] firmware/sysfb: Set firmware-framebuffer parent device

[Sui Jingfeng]

Hi,


On 2024/2/2 19:58, Thomas Zimmermann wrote:
> Set the firmware framebuffer's parent device, which usually is the
> graphics hardware's physical device. Integrates the framebuffer in
> the Linux device hierarchy and lets Linux handle dependencies among
> devices. For example, the graphics hardware won't be suspended while
> the firmware device is still active.

This is a very nice benefit, I can't agree more!

Because the backing memory of the firmware framebuffer occupied
belongs to the graphics hardware itself. For PCIe device, the
backing memory is typically the dedicated VRAM of the PCIe GPU.
But there are some exceptions, for example, the gma500. But I
think this can be fixed in the future, as majority(>99.9%) PCIe
GPU has the a dedicated VRAM.


For ARM and ARM64 platform device, the backing memory of the
firmware framebuffer may located at the system RAM. It's common
that the display controller is a platform device in the embedded
world. So I think the sysfb_parent_dev() function can be extended
to be able to works for platform device in the future.