get_ro() callback must return values >= 0 for its logical state, 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 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 <[EMAIL PROTECTED]>
---
 drivers/mmc/core/sd.c       |    4 ++--
 drivers/mmc/host/at91_mci.c |    2 +-
 drivers/mmc/host/imxmmc.c   |    9 ++++++---
 drivers/mmc/host/mmc_spi.c  |    9 ++++++---
 drivers/mmc/host/pxamci.c   |    9 ++++++---
 include/linux/mmc/host.h    |    3 +++
 6 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 7ef3b15..b122eb9 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 a28fc2f..a2ccdf2 100644
--- a/drivers/mmc/host/at91_mci.c
+++ b/drivers/mmc/host/at91_mci.c
@@ -794,7 +794,7 @@ static int at91_mci_get_ro(struct mmc_host *mmc)
        struct at91mci_host *host = mmc_priv(mmc);
 
        if (host->board->wp_pin) {
-               read_only = gpio_get_value(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") );
        }
diff --git a/drivers/mmc/host/imxmmc.c b/drivers/mmc/host/imxmmc.c
index 95f33e8..5167679 100644
--- a/drivers/mmc/host/imxmmc.c
+++ b/drivers/mmc/host/imxmmc.c
@@ -889,9 +889,12 @@ 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 f0f86b1..a804c7f 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 65210fc..b6056bd 100644
--- a/drivers/mmc/host/pxamci.c
+++ b/drivers/mmc/host/pxamci.c
@@ -361,9 +361,12 @@ 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/include/linux/mmc/host.h b/include/linux/mmc/host.h
index f2e9885..ef3b773 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -55,6 +55,9 @@ struct mmc_host_ops {
         * 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.
+        *
+        * .get_ro and .get_cd should return >= 0 for their logical values,
+        * or negative errno value in case of error.
         */
        void    (*set_ios)(struct mmc_host *host, struct mmc_ios *ios);
        int     (*get_ro)(struct mmc_host *host);
-- 
1.5.5.1
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