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>

7 files changed, 40 insertions, 23 deletions

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 7ef3b15c5e3d..b122eb9ea453 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -494,13 +494,13 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
          * Check if read-only switch is active.
          */
         if (!oldcard) {
-                if (!host->ops->get_ro) {
+                if (!host->ops->get_ro || host->ops->get_ro(host) < 0) {
                         printk(KERN_WARNING "%s: host does not "
                                 "support reading read-only "
                                 "switch. assuming write-enable.\n",
                                 mmc_hostname(host));
                 } else {
-                        if (host->ops->get_ro(host))
+                        if (host->ops->get_ro(host) > 0)
                                 mmc_card_set_readonly(card);
                 }
         }
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 = {
diff --git a/drivers/mmc/host/imxmmc.c b/drivers/mmc/host/imxmmc.c
index eed211b2ac70..5e880c0f1349 100644
--- a/drivers/mmc/host/imxmmc.c
+++ b/drivers/mmc/host/imxmmc.c
@@ -892,9 +892,12 @@ static int imxmci_get_ro(struct mmc_host *mmc)
         struct imxmci_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;
 }
 
 
diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
index 547eb857b1b3..4e82f64a96bc 100644
--- a/drivers/mmc/host/mmc_spi.c
+++ b/drivers/mmc/host/mmc_spi.c
@@ -1126,9 +1126,12 @@ static int mmc_spi_get_ro(struct mmc_host *mmc)
         struct mmc_spi_host *host = mmc_priv(mmc);
 
         if (host->pdata && host->pdata->get_ro)
-                return host->pdata->get_ro(mmc->parent);
-        /* board doesn't support read only detection; assume writeable */
-        return 0;
+                return !!host->pdata->get_ro(mmc->parent);
+        /*
+         * Board doesn't support read only detection; let the mmc core
+         * decide what to do.
+         */
+        return -ENOSYS;
 }
 
 static int mmc_spi_get_cd(struct mmc_host *mmc)
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)
diff --git a/drivers/mmc/host/wbsd.c b/drivers/mmc/host/wbsd.c
index c303e7f57ab4..67e5a9b80f53 100644
--- a/drivers/mmc/host/wbsd.c
+++ b/drivers/mmc/host/wbsd.c
@@ -939,7 +939,7 @@ static int wbsd_get_ro(struct mmc_host *mmc)
 
         spin_unlock_bh(&host->lock);
 
-        return csr & WBSD_WRPT;
+        return !!(csr & WBSD_WRPT);
 }
 
 static const struct mmc_host_ops wbsd_ops = {
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 6188e19d2331..753b7231b887 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -58,6 +58,18 @@ struct mmc_host_ops {
          *
          * Also note that these functions might sleep, so don't call them
          * in the atomic contexts!
+         *
+         * Return values for the get_ro callback should be:
+         *   0 for a read/write card
+         *   1 for a read-only card
+         *   -ENOSYS when not supported (equal to NULL callback)
+         *   or a negative errno value when something bad happened
+         *
+         * Return values for the get_ro callback should be:
+         *   0 for a absent card
+         *   1 for a present card
+         *   -ENOSYS when not supported (equal to NULL callback)
+         *   or a negative errno value when something bad happened
          */
         void    (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
         int     (*get_ro)(struct mmc_host *host);