mmc: change .get_ro() callback semantics

Now get_ro() callback must return 0/1 values for its logical states, and
negative errno values in case of error. If particular host instance doesn't
support RO/WP switch, it should return -ENOSYS.

This patch changes some hosts in two ways:

1. Now functions should be smart to not return negative values in
   "RO asserted" case (particularly gpio_ calls could return negative
   values for the outermost GPIOs).

   Also, board code usually passes get_ro() callbacks that directly return
   gpioreg & bit result, so at91_mci, imxmmc, pxamci and mmc_spi's get_ro()
   handlers need take special care when returning platform's values to the
   mmc core.

2. In case of host instance didn't implement get_ro() callback, it should
   really return -ENOSYS and let the mmc core decide what to do about it
   (mmc core thinks the same way as the hosts, so it isn't functional
   change).

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

1 files changed, 7 insertions, 11 deletions

diff --git a/drivers/mmc/host/at91_mci.c b/drivers/mmc/host/at91_mci.c
index 8979ad330a4d..b9d4ed6b29b1 100644
--- a/drivers/mmc/host/at91_mci.c
+++ b/drivers/mmc/host/at91_mci.c
@@ -793,19 +793,15 @@ static irqreturn_t at91_mmc_det_irq(int irq, void *_host)
 
 static int at91_mci_get_ro(struct mmc_host *mmc)
 {
-        int read_only = 0;
         struct at91mci_host *host = mmc_priv(mmc);
 
-        if (host->board->wp_pin) {
-                read_only = gpio_get_value(host->board->wp_pin);
-                printk(KERN_WARNING "%s: card is %s\n", mmc_hostname(mmc),
-                                (read_only ? "read-only" : "read-write") );
-        }
-        else {
-                printk(KERN_WARNING "%s: host does not support reading read-only "
-                                "switch.  Assuming write-enable.\n", mmc_hostname(mmc));
-        }
-        return read_only;
+        if (host->board->wp_pin)
+                return !!gpio_get_value(host->board->wp_pin);
+        /*
+         * Board doesn't support read only detection; let the mmc core
+         * decide what to do.
+         */
+        return -ENOSYS;
 }
 
 static const struct mmc_host_ops at91_mci_ops = {