Framebuffer mmap on PowerPC

[Thomas Zimmermann]

Hi,

there's a per-architecture function called fb_pgprotect() that sets 
VMA's vm_page_prot for mmaped framebuffers. Most architectures use a 
simple implementation based on pgprot_writecomine() [1] or 
pgprot_noncached(). [2]

On PPC this function uses phys_mem_access_prot() and therefore requires 
the mmap call's file struct. [3] Removing the file argument would help 
with simplifying the caller of fb_pgprotect(). [4]

Why is the file even required on PPC?

Is it possible to replace phys_mem_access_prot() with something simpler 
that does not use the file struct?

Best regards
Thomas


[1] 
https://elixir.bootlin.com/linux/v6.5/source/include/asm-generic/fb.h#L19
[2] 
https://elixir.bootlin.com/linux/v6.5/source/arch/mips/include/asm/fb.h#L11
[3] 
https://elixir.bootlin.com/linux/v6.5/source/arch/powerpc/include/asm/fb.h#L12
[4] 
https://elixir.bootlin.com/linux/v6.5/source/drivers/video/fbdev/core/fbmem.c#L1299


-- 
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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