Re: [PATCH] fbcon: Re-fix little-endian bogosity in slow_imageblit()
From: Andrew Morton <hidden>
Date: 2006-11-03 18:59:14
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On Fri, 03 Nov 2006 15:55:34 +0100 Franck Bui-Huu [off-list ref] wrote:
From: Franck Bui-Huu <redacted> 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.
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--- 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.
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--- 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. ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642