[RFC v3 1/3] fbmem: add default get_fb_unmapped_area function

[Benjamin Gaignard]

2016-12-01 2:13 GMT+01:00 Laurent Pinchart <laurent.pinchart at ideasonboard.com>:
> Hi Benjamin,
>
> On Wednesday 30 Nov 2016 20:46:23 Benjamin Gaignard wrote:
>> 2016-11-30 20:39 GMT+01:00 Laurent Pinchart:
>> > On Wednesday 30 Nov 2016 20:34:17 Benjamin Gaignard wrote:
>> >> If HAVE_ARCH_FB_UNMAPPED_AREA is set and get_fb_unmapped_area
>> >> function not defined in platform architecture let use a default function.
>> >>
>> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard at linaro.org>
>> >> ---
>> >>
>> >>  drivers/video/fbdev/core/fbmem.c | 15 +++++++++++++++
>> >>  1 file changed, 15 insertions(+)
>> >>
>> >> diff --git a/drivers/video/fbdev/core/fbmem.c
>> >> b/drivers/video/fbdev/core/fbmem.c index 76c1ad9..54488ee 100644
>> >> --- a/drivers/video/fbdev/core/fbmem.c
>> >> +++ b/drivers/video/fbdev/core/fbmem.c
>> >> @@ -1492,6 +1492,21 @@ static long fb_compat_ioctl(struct file *file,
>> >> unsigned int cmd,
>> >>    return 0;
>> >>  }
>> >>
>> >> +#if defined(HAVE_ARCH_FB_UNMAPPED_AREA) &&
>> >> !defined(get_fb_unmapped_area)
>> >
>> > I think I've asked this twice already, how is that possible ?
>>
>> As you said before only sparc and blackfin architectures have define
>> HAVE_ARCH_FB_UNMAPPED_AREA and get_fb_unmapped_area().
>> For stm32f4 (ARMv7m) I plan to only add HAVE_ARCH_FB_UNMAPPED_AREA and
>> use this default function
>
> Ah, so it's for support of a future patch. You should explain that in the
> commit message.

OK

> The other question I asked was whether it would be possible to come up with a
> generic implementation of this function that would work on all architectures.
> At first sight the blackfin implementation is similar, but the sparc one is
> quite different. Why does it have to be arch-specific ?

I don't know but I guess it is link to how memory is mmapped by the
architecture

>> By testing those two flags I avoid to define twince
>> get_fb_unmapped_area() if the architecture already
>> provide it.
>>
>> >> +unsigned long get_fb_unmapped_area(struct file *filp,
>> >> +                                unsigned long addr, unsigned long len,
>> >> +                                unsigned long pgoff, unsigned long
>> >> flags)
>> >> +{
>> >> +     struct fb_info * const info = filp->private_data;
>> >> +     unsigned long fb_size = PAGE_ALIGN(info->fix.smem_len);
>> >> +
>> >> +     if (pgoff > fb_size || len > fb_size - pgoff)
>> >> +             return -EINVAL;
>> >> +
>> >> +     return (unsigned long)info->screen_base + pgoff;
>> >> +}
>> >> +#endif
>> >> +
>> >>  static const struct file_operations fb_fops = {
>> >>       .owner =        THIS_MODULE,
>> >>       .read =         fb_read,
>
> --
> Regards,
>
> Laurent Pinchart
>



-- 
Benjamin Gaignard

Graphic Study Group

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