1 files changed, 12 insertions, 0 deletions

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);