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, 6 insertions, 3 deletions

diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c
index d89475d36988..d39f59738866 100644
--- a/drivers/mmc/host/pxamci.c
+++ b/drivers/mmc/host/pxamci.c
@@ -374,9 +374,12 @@ static int pxamci_get_ro(struct mmc_host *mmc)
 	struct pxamci_host *host = mmc_priv(mmc);
 
 	if (host->pdata && host->pdata->get_ro)
-		return host->pdata->get_ro(mmc_dev(mmc));
-	/* Host doesn't support read only detection so assume writeable */
-	return 0;
+		return !!host->pdata->get_ro(mmc_dev(mmc));
+	/*
+	 * Board doesn't support read only detection; let the mmc core
+	 * decide what to do.
+	 */
+	return -ENOSYS;
 }
 
 static void pxamci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)