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    SubjectRe: [MMC] Multiple cards on one host
    On Wed, 3 Sep 2008 10:43:43 +0200
    Sascha Hauer <> wrote:

    > Hi,
    > I have a board (PXA based) which has two SD slots. It uses a gpio to
    > switch between the slots. In times when the MMC subsystem implemented
    > the bus topology our customer used this fact to connect the two slots on
    > a single host (although it was never intended to work with SD cards, it
    > seemed to work). Any idea how to implement this on recent kernels? I
    > thought about registering two hosts in pxamci.c, but this seems quite
    > hacky and I suppose I'll run into locking trouble.

    To be honest, I don't think you can sanely support it. The OMAP guys
    have been playing with some kind of multiplexer in front of the
    controller, but it just seems like a world of hurt to me.

    Perhaps you can convert to using SPI for the second slot if the
    customer really needs a design with two slots?

    -- Pierre Ossman

    Linux kernel, MMC maintainer
    rdesktop, core developer

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