On Thu, Jun 29, 2023, at 15:01, Thomas Zimmermann wrote:

Am 29.06.23 um 14:35 schrieb Arnd Bergmann:

quoted

On Thu, Jun 29, 2023, at 13:45, Thomas Zimmermann wrote:

quoted

The global variable edid_info contains the firmware's EDID information
as an extension to the regular screen_info on x86. Therefore move it to
<asm/screen_info.h>.

Add the Kconfig token ARCH_HAS_EDID_INFO to guard against access on
architectures that don't provide edid_info. Select it on x86.

I'm not sure we need another symbol in addition to
CONFIG_FIRMWARE_EDID. Since all the code behind that
existing symbol is also x86 specific, would it be enough
to just add either 'depends on X86' or 'depends on X86 ||
COMPILE_TEST' there?

FIRMWARE_EDID is a user-selectable feature, while ARCH_HAS_EDID_INFO 
announces an architecture feature. They do different things.

I still have trouble seeing the difference.

Right now, ARCH_HAS_EDID_INFO only works on the old BIOS-based VESA 
systems. In the future, I want to add support for EDID data from EFI and 
OF as well. It would be stored in edid_info. I assume that the new 
symbol will become useful then.

I don't see why an OF based system would have the same limitation
as legacy BIOS with supporting only a single monitor, if we need
to have a generic representation of EDID data in DT, that would
probably be in a per device property anyway.

I suppose you could use FIRMWARE_EDID on EFI or OF systems without
the need for a global edid_info structure, but that would not
share any code with the current fb_firmware_edid() function.

     Arnd