On Dec 6, 2008, at 4:34 AM, Hans Petter Selasky wrote: > Hi, > > After various feedback from several people I have made a new patch > proposal > that will fix the busdma problem. > > See: > > http://perforce.freebsd.org/chv.cgi?CH=154181 > > Review wanted! The USB stack has a fixed page size of 4K. On our 64-bit platforms PAGE_SIZE is at least 8K. Your change is sloppy in that respect and doesn't make the distinction. That makes the patch a kluge. The definition of BUS_DMA_NO_REALIGN is based on circumstantial evidence only and as such, works as a side-effect. I don't think that's a good design. I don't think there's any reason not to preserve the page offset in all cases. So far all hardware worked whether or not their DMA pages were bounced and the non-bounced pages would have a possible non-zero page offset, whereas the bounced pages would always have a zero page offset. In short: it works either way. In particular, it works with the page offset preserved. Why not preserve it always? What's the downside? -- Marcel Moolenaar xcllnt_at_mac.comReceived on Sat Dec 06 2008 - 16:45:06 UTC
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