Hi Arnd Am 30.06.23 um 13:53 schrieb Arnd Bergmann:
On Fri, Jun 30, 2023, at 09:46, Thomas Zimmermann wrote:Am 29.06.23 um 15:21 schrieb Arnd Bergmann:On Thu, Jun 29, 2023, at 15:01, Thomas Zimmermann wrote:Am 29.06.23 um 14:35 schrieb Arnd Bergmann:On Thu, Jun 29, 2023, at 13:45, Thomas Zimmermann wrote: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.The idea here is that ARCH_HAS_ signals the architecture's support for the feature. Drivers set 'depends on' in their Kconfig. Another Kconfig token, VIDEO_SCREEN_INFO or FIRMWARE_EDID, would then actually enable the feature. Drivers select VIDEO_SCREEN_INFO or FIRMWARE_EDID and the architectures contains code likeFair enough. In that case, I guess FIRMWARE_EDID will just depend on ARCH_HAS_EDID_INFO, or possibly "depends on FIRMWARE_EDID || EFI" after it starts calling into an EFI specific function, right?#ifdef VIDEO_SCREEN_INFO struct screen_info screen_info = { /* set values here */ } #endif This allows us to disable code that requires screen_info/edid_info, but also disable screen_info/edid_info unless such code has been enabled in the kernel config. Some architectures currently mimic this by guarding screen_info with ifdef CONFIG_VT or similar. I'd like to make this more flexible. The cost of a few more internal Kconfig tokens seems negligible.I definitely get it for the screen_info, which needs the complexity. For ARCHARCH_HAS_EDID_INFO I would hope that it's never selected by anything other than x86, so I would still go with just a dependency on x86 for simplicity, but I don't mind having the extra symbol if that keeps it more consistent with how the screen_info is handled.
Well, I'd like to add edid_info to platforms with EFI. What would be arm/arm64 and loongarch, I guess. See below for the future plans.
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.The current code is build on top of screen_info and edid_info. I'd preferably not replace that, if possible.One way I could imagine this looking in the end would be something like struct screen_info *fb_screen_info(struct device *dev) { struct screen_info *si = NULL; if (IS_ENABLED(CONFIG_EFI)) si = efi_get_screen_info(dev); if (IS_ENABLED(CONFIG_ARCH_HAS_SCREEN_INFO) && !si) si = screen_info; return si; } corresponding to fb_firmware_edid(). With this, any driver that wants to access screen_info would call this function instead of using the global pointer, plus either NULL pointer check or a CONFIG_ARCH_HAS_SCREEN_INFO dependency. This way we could completely eliminate the global screen_info on arm64, riscv, and loongarch but still use the efi and hyperv framebuffer/drm drivers.
If possible, I'd like to remove global screen_info and edid_info entirely from fbdev and the various consoles.
We currently use screen_info to set up the generic framebuffer device in drivers/firmware/sysfb.c. I'd like to use edid_info here as well, so that the generic graphics drivers can get EDID information.
For the few fbdev drivers and consoles that require the global screen_info/edid_info, I'd rather provide lookup functions in sysfb (e.g., sysfb_get_screen_info(), sysfb_get_edid_info()). The global screen_info/edid_info state would then become an internal artifact of the sysfb code.
Hopefully that explains some of the decisions made in this patchset. Best regards Thomas
Arnd
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
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