mmc: add support for card-detection polling

Some hosts (and boards that use mmc_spi) do not use interrupts on the CD
line, so they can't trigger mmc_detect_change. We want to poll the card
and see if there was a change. 1 second poll interval seems resonable.

This patch also implements .get_cd() host operation, that could be used
by the hosts that are able to report card-detect status without need to
talk MMC.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 7ab962fa1d73..6188e19d2331 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -51,8 +51,18 @@ struct mmc_ios {
 
 struct mmc_host_ops {
         void    (*request)(struct mmc_host *host, struct mmc_request *req);
+        /*
+         * Avoid calling these three functions too often or in a "fast path",
+         * since underlaying controller might implement them in an expensive
+         * and/or slow way.
+         *
+         * Also note that these functions might sleep, so don't call them
+         * in the atomic contexts!
+         */
         void    (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
         int     (*get_ro)(struct mmc_host *host);
+        int     (*get_cd)(struct mmc_host *host);
+
         void    (*enable_sdio_irq)(struct mmc_host *host, int enable);
 };
 
@@ -94,6 +104,7 @@ struct mmc_host {
 #define MMC_CAP_SD_HIGHSPEED    (1 << 3)        /* Can do SD high-speed timing */
 #define MMC_CAP_SDIO_IRQ        (1 << 4)        /* Can signal pending SDIO IRQs */
 #define MMC_CAP_SPI             (1 << 5)        /* Talks only SPI protocols */
+#define MMC_CAP_NEEDS_POLL      (1 << 6)        /* Needs polling for card-detection */
 
         /* host specific block data */
         unsigned int            max_seg_size;   /* see blk_queue_max_segment_size */