Re: [PATCH][1/2] usb: dma bounce buffer support V3 | |
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On Tue, 22 Jan 2008 15:12:53 +0900 "Magnus Damm" <magnus.damm@xxxxxxxxx> wrote: > On Jan 22, 2008 2:01 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 22 Jan 2008 12:20:10 +0900 Magnus Damm <magnus.damm@xxxxxxxxx> wrote: > > > > > usb: dma bounce buffer support V3 > > > > > > This patch adds dma bounce buffer support to the usb core. These buffers > > > can be enabled with the HCD_LOCAL_MEM flag, and they make sure that all data > > > passed to the host controller is allocated using dma_alloc_coherent(). > > > > It is unobvious (to me) why this code uses put_unaligned() and > > get_unaligned() in the places where it does. So I'll assume that it will > > be unobvious to other reviewers and readers. > > The HCD_LOCAL_MEM dma bounce buffer code is using unaligned functions > to temporarily save a pointer at the end of the dma data buffer. > hcd_alloc_coherent() saves the pointer which is needed by > hcd_free_coherent(). The unaligned functions are used because the size > of the buffer may be uneven. > > It's of course possible to round up the size instead and use aligned > access if you prefer that. The memory area used for dma may be limited > though so I felt it was natural to optimize for small memory footprint > over access speed. that wasn't a patch ;) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ linux-usb-devel@xxxxxxxxxxxxxxxxxxxxx To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
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