Hi Am 02.05.23 um 22:06 schrieb Arnd Bergmann:
On Tue, May 2, 2023, at 15:02, Thomas Zimmermann wrote:Implement framebuffer I/O helpers, such as fb_read*() and fb_write*(), in the architecture's <asm/fb.h> header file or the generic one. The common case has been the use of regular I/O functions, such as __raw_readb() or memset_io(). A few architectures used plain system- memory reads and writes. Sparc used helpers for its SBus. The architectures that used special cases provide the same code in their __raw_*() I/O helpers. So the patch replaces this code with the __raw_*() functions and moves it to <asm-generic/fb.h> for all architectures. v3: * implement all architectures with generic helpers * support reordering and native byte order (Geert, Arnd)This looks good for the read/write helpers, but I'm a little worried about the memset and memcpy functions, since they do change behavior on some architectures: - on sparc64, fb_mem{set,cpy} uses ASI_PHYS_BYPASS_EC_E (like __raw_readb) while mem{set_,cpy_from,cpy_to} uses ASI_PHYS_BYPASS_EC_E_L (like readb) I don't know the effect of that, but it seems intentional - on loongarch and csky, the _io variants avoid unaligned access, while the normal memcpy/memset is probably broken, so your patch is a bugfix - on ia64, the _io variants use bytewise access and avoid any longer loads and stores, so your patch probably makes things slower. It's probably safe to deal with all the above by either adding architecture specific overrides to the current version, or by doing the semantic changes before the move to asm/fb.h, but one way or the other I'd prefer this to be separate from the consolidation patch that should not have any changes in behavior.
I think I'll add architecture overrides that contain the current code, even if they contain some force-casting wrt __iomem. If anyone wants to fix the issues, they can then address them easily.
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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