Re: [PATCH 7/32] mmc: add host capabilities for SD only and MMC only

Matt Fleming
2009-07-25T15:54:02Z

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.