Messages in this thread | | | Date | Fri, 3 Nov 2006 10:58:57 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] fbcon: Re-fix little-endian bogosity in slow_imageblit() |
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On Fri, 03 Nov 2006 15:55:34 +0100 Franck Bui-Huu <vagabon.xyz@gmail.com> wrote:
> From: Franck Bui-Huu <fbuihuu@gmail.com> > > 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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