On Fri, 03 Nov 2006 15:55:34 +0100
Franck Bui-Huu <[email protected]> wrote:
> From: Franck Bui-Huu <[email protected]>
>
> This bug has been introduced by commit:
>
> a536093a2f07007aa572e922752b7491b9ea8ff2
>
> This commit fixed the big-endian case but broke the little-endian one.
> This patch revert the previous change and swap the definition of
> FB_BIT_NR() macro between big and little endian. It should work for
> both endianess now.
>
I get worried when I see the word "should" in a changelog.
> ---
>
> This is the most obvious fix for me although it's a bit weird
> that bit ordering depend on platform endianess. I don't know
> fb code so I prefer submitting this trivial fix rather than
> breaking every thing else ;)
>
> drivers/video/cfbimgblt.c | 4 ++--
> include/linux/fb.h | 2 ++
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/cfbimgblt.c b/drivers/video/cfbimgblt.c
> index 51d3538..8f47bf4 100644
> --- a/drivers/video/cfbimgblt.c
> +++ b/drivers/video/cfbimgblt.c
> @@ -168,7 +168,7 @@ static inline void slow_imageblit(const
>
> while (j--) {
> l--;
> - color = (*s & (1 << l)) ? fgcolor : bgcolor;
> + color = (*s & (1 << FB_BIT_NR(l))) ? fgcolor : bgcolor;
> val |= FB_SHIFT_HIGH(color, shift);
So that takes us back to the pre-March 31 code, which was allegedly broken
on big-endian.
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -854,10 +854,12 @@ #define fb_memset memset
> #endif
>
> #if defined (__BIG_ENDIAN)
> +#define FB_BIT_NR(b) (b)
> #define FB_LEFT_POS(bpp) (32 - bpp)
> #define FB_SHIFT_HIGH(val, bits) ((val) >> (bits))
> #define FB_SHIFT_LOW(val, bits) ((val) << (bits))
> #else
> +#define FB_BIT_NR(b) (7 - (b))
> #define FB_LEFT_POS(bpp) (0)
> #define FB_SHIFT_HIGH(val, bits) ((val) << (bits))
> #define FB_SHIFT_LOW(val, bits) ((val) >> (bits))
And that swaps the little-endian and bit-endian implementations of
FB_BIT_NR(). So if it was previously broken on big-endian and was working
on little-endian then it's presumably now broken on little-endian and
working on big-endian. Or something.
-
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