Interesting coincidence that the value of MMC_TYPE_SD and MMC_TYPE_SDIO
and MMC_TYPE_SD_COMBO have the relationship that SD_COMBO is the bitwise
OR of the other two. However, this seems to be more of a coincidence
than intentional. The #defines were clearly meant to be numeric values
rather than bit-masks.
#define MMC_TYPE_MMC 0 /* MMC card */
#define MMC_TYPE_SD 1 /* SD card */
#define MMC_TYPE_SDIO 2 /* SDIO card */
#define MMC_TYPE_SD_COMBO 3 /* SD combo (IO+mem) card */
Using the bit-mask approach therefore doesn't feel like the natural way
to me. Perhaps the #defines could be changed to
#define MMC_TYPE_MMC (1 << 0) /* MMC card */
#define MMC_TYPE_SD (1 << 1) /* SD card */
#define MMC_TYPE_SDIO (1 << 2) /* SDIO card */
#define MMC_TYPE_SD_COMBO (MMC_TYPE_SD | MMC_TYPE_SDIO) /* SD
combo (IO+mem) card */
Thanks,
Prashanth
On Wednesday 04 May 2011 04:53 PM, Michał Mirosław wrote:
On Tue, May 03, 2011 at 05:00:03PM +0530, Prashanth Bhat wrote:
To be more specific, I would think that the code change required in
include/linux/mmc/card.h is:
#define mmc_card_mmc(c) ((c)->type == MMC_TYPE_MMC)
- #define mmc_card_sd(c) ((c)->type == MMC_TYPE_SD)
- #define mmc_card_sdio(c) ((c)->type == MMC_TYPE_SDIO)
+ #define mmc_card_sd(c) ((c)->type == MMC_TYPE_SD ||
(c)->type == MMC_TYPE_SD_COMBO)
+ #define mmc_card_sdio(c) ((c)->type == MMC_TYPE_SDIO ||
(c)->type == MMC_TYPE_SD_COMBO)
You can actually use (c->type& MMC_TYPE_SD) and (c->type& MMC_TYPE_SDIO).
Unless there will be more types of SD cards (unlikely) this way
will generate less code on average.
Best Regards,
Michał Mirosław
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