linux-kernel - Re: [PATCH v2] video: fbdev: controlfb: fix build for COMPILE_TEST=y && PPC

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Date:   Wed, 29 Apr 2020 13:54:17 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        kbuild test robot <lkp@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] video: fbdev: controlfb: fix build for COMPILE_TEST=y
 && PPC_PMAC=y && PPC32=n

Hi Bartlomiej.

On Wed, Apr 29, 2020 at 12:48:24PM +0200, Bartlomiej Zolnierkiewicz wrote:
> 
> powerpc allyesconfig fails like this:
> 
> drivers/video/fbdev/controlfb.c: In function 'controlfb_mmap':
> drivers/video/fbdev/controlfb.c:756:23: error: implicit declaration of function 'pgprot_cached_wthru'; did you mean 'pgprot_cached'? [-Werror=implicit-function-declaration]
>   756 |   vma->vm_page_prot = pgprot_cached_wthru(vma->vm_page_prot);
>       |                       ^~~~~~~~~~~~~~~~~~~
>       |                       pgprot_cached
> drivers/video/fbdev/controlfb.c:756:23: error: incompatible types when assigning to type 'pgprot_t' {aka 'struct <anonymous>'} from type 'int'
> 
> Fix it by adding missing PPC32 dependency.

Is this really the right fix?
Short term I htink it is OK, but I think there should be a common way
to do the same for all archtectures so no conditional compilation is
needed. In other words the use of pgprot_cached_wthru looks like we
need a better abstraction.

Added Christoph to the mail as he has a good overview of the area.

	Sam


> 
> Fixes: a07a63b0e24d ("video: fbdev: controlfb: add COMPILE_TEST support")
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Reported-by: kbuild test robot <lkp@...el.com>
> Cc: Sam Ravnborg <sam@...nborg.org>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> ---
> v2: fix implicit btext_update_display() function declaration error
> 
>  drivers/video/fbdev/controlfb.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: b/drivers/video/fbdev/controlfb.c
> ===================================================================
> --- a/drivers/video/fbdev/controlfb.c
> +++ b/drivers/video/fbdev/controlfb.c
> @@ -55,7 +55,7 @@
>  #include "macmodes.h"
>  #include "controlfb.h"
>  
> -#ifndef CONFIG_PPC_PMAC
> +#if !defined(CONFIG_PPC_PMAC) || !defined(CONFIG_PPC32)
>  #define invalid_vram_cache(addr)
>  #undef in_8
>  #undef out_8