Messages in this thread | | | Date | Mon, 25 Aug 2003 15:43:04 -0400 | From | Arvind Sankar <> | Subject | vesafb mtrr setup question |
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The following lines are pulled out of drivers/video/vesafb.c (2.4.20): Line 646 onwards..
> if (mtrr) { > int temp_size = video_size; > /* Find the largest power-of-two */ > while (temp_size & (temp_size - 1)) > temp_size &= (temp_size - 1); > In the first place, the power of two computation computes the largest power of 2 that is _smaller_ than video_size, so it looks like an off-by-1 bug.
> /* Try and find a power of two to add */ > while (temp_size && mtrr_add(video_base, temp_size, MTRR_TYPE_WRCOMB, 1)==-EINVAL) { > temp_size >>= 1; > } > }
Secondly, what's the point of requesting a smaller write-combining segment that won't cover all the video memory being used? If it fails the first time round, shouldn't we either give up or attempt requesting several contiguous segments?
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