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    SubjectRe: [PATCH v3 RESEND] dma-mapping: add new API for max_segment_number
    On Fri, 17 Jun 2011 06:40:35 -0600
    Matthew Wilcox <> wrote:

    > On Thu, Jun 16, 2011 at 08:30:53PM +0800, Shawn Guo wrote:
    > > Here is the user story that tells the need of the new api. The
    > > mxs-mmc is the mmc host controller for Freescale MXS architecture.
    > > There are a pair of mmc host specific parameters max_seg_size and
    > > max_segs that mxs-mmc host driver needs to tell mmc core, so that
    > > mmc core can know how big each data segment could be and how many
    > > segments could be handled one time in a scatter list by host driver.
    > >
    > > The mxs-mmc driver is one user of dmaengine mxs-dma, and it will call
    > > mxs-dma to transfer data in scatter list. That is to say mxs-mmc has
    > > no idea of what max_seg_size and max_segs should be, because they are
    > > all mxs-dma capability parameters, and mxs-mmc needs to query them
    > > from mxs-dma.
    > This approach would make sense if mxs-mmc were generic, but it's tied to
    > mxs-dma, so it can just as well call mxs-dma to find out how many segments
    > it supports.

    SCSI HBA drivers stores the max number of sg entries in
    host->sg_tablesize (and scsi-ml tells the block layer about the
    limit)? So if we have the generic API to handle the value, scsi HBA
    drivers (and scsi-ml) could use it too?

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