Re: [PATCH v2 01/19] fbdev: Prepare generic architecture helpers

Arnd Bergmann
2023-04-17T09:32:54Z

On Mon, Apr 17, 2023, at 11:03, Thomas Zimmermann wrote:
> Am 11.04.23 um 10:08 schrieb Geert Uytterhoeven:
>> On Thu, Apr 6, 2023 at 4:30 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:

>>> +#ifndef fb_pgprotect
>>> +#define fb_pgprotect fb_pgprotect
>>> +static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
>>> + unsigned long off)
>>
>> Does this affect any noMMU platforms that relied on fb_pgprotect()
>> doing nothing before?
>> Perhaps the body below should be protected by "#ifdef CONFIG_MMU"?
>
> I cannot conclusively answer this question, but I did some grep'ing
> ('git grep ndef | grep CONFIG_MMU'):
>
> Only the architectures in this patchset provide <asm/fb.h> but nothing
> anywhere uses <asm-generic/fb.h> yet. And of those architectures, only
> arm and m68k have !CONFIG_MMU cases. Those are handled in the rsp
> patches. I think we're good.

Agreed. The generic version is just a more elaborate way to do
nothing here, as the

vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

line on nommu just turns into a self-assignment of the same member
that was set the line before.

Arnd