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    SubjectRe: [PATCH 7/32] mmc: add host capabilities for SD only and MMC only
    On Fri, Jul 10, 2009 at 03:40:54PM +0300, Adrian Hunter wrote:
    >
    > Some hosts can accept only certain types of cards.
    > For example, an eMMC is MMC only and a uSD slot may
    > be SD only. However the MMC card scanning logic
    > checks for all card types one by one.
    >
    > Add host capabilities to specify which card types
    > cannot be used, and amend the card scanning logic
    > to skip scanning for those types.
    >

    I'm only nitpicking here, but I think that logic is a little inverted.
    By saying which cards cannot be used (as opposed to which cards can be
    used), we get conditionals like this,

    >
    > - mmc_send_if_cond(host, host->ocr_avail);
    > + if (!(host->caps & MMC_CAP_NOT_SDIO) || !(host->caps & MMC_CAP_NOT_SD))
    > + mmc_send_if_cond(host, host->ocr_avail);
    > +

    Whilst reviewing this patch it took my brain a few too many seconds to
    parse that as "if the host is capable of SDIO or SD".


    > diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
    > index 0a60b02..e996967 100644
    > --- a/include/linux/mmc/host.h
    > +++ b/include/linux/mmc/host.h
    > @@ -150,6 +150,13 @@ struct mmc_host {
    > #define MMC_CAP_DISABLE (1 << 7) /* Can the host be disabled */
    > #define MMC_CAP_NONREMOVABLE (1 << 8) /* Nonremovable e.g. eMMC */
    > #define MMC_CAP_WAIT_WHILE_BUSY (1 << 9) /* Waits while card is busy */
    > +#define MMC_CAP_NOT_SDIO (1 << 10) /* Card cannot be SDIO */
    > +#define MMC_CAP_NOT_SD (1 << 11) /* Card cannot be SD */
    > +#define MMC_CAP_NOT_MMC (1 << 12) /* Card cannot be MMC */
    > +
    > +#define MMC_CAP_SDIO_ONLY (MMC_CAP_NOT_SD | MMC_CAP_NOT_MMC)
    > +#define MMC_CAP_SD_ONLY (MMC_CAP_NOT_SDIO | MMC_CAP_NOT_MMC)
    > +#define MMC_CAP_MMC_ONLY (MMC_CAP_NOT_SDIO | MMC_CAP_NOT_SD)
    >

    And by saying what capabilities a host supports, when we add new
    capabilities we don't have to modify existing code to say that it
    doesn't support the new capability.


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