genhd: expose AN to user space

Allow user space to determine if a disk supports Asynchronous Notification of
media changes.  This is done by adding a new sysfs file "capability_flags",
which is documented in (insert file name).  This sysfs file will export all
disk capabilities flags to user space.  We also define a new flag to define
the media change notification capability.

Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 25 insertions, 1 deletions

diff --git a/Documentation/block/capability.txt b/Documentation/block/capability.txt
new file mode 100644
index 000000000000..2f1729424ef4
--- /dev/null
+++ b/Documentation/block/capability.txt
@@ -0,0 +1,15 @@
+Generic Block Device Capability
+===============================================================================
+This file documents the sysfs file block/<disk>/capability
+
+capability is a hex word indicating which capabilities a specific disk
+supports.  For more information on bits not listed here, see
+include/linux/genhd.h
+
+Capability                              Value
+-------------------------------------------------------------------------------
+GENHD_FL_MEDIA_CHANGE_NOTIFY            4
+        When this bit is set, the disk supports Asynchronous Notification
+        of media change events.  These events will be broadcast to user
+        space via kernel uevent.
+
diff --git a/block/genhd.c b/block/genhd.c
index 93a2cf654597..7efa8bb25da9 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -423,7 +423,10 @@ static ssize_t disk_size_read(struct gendisk * disk, char *page)
 {
         return sprintf(page, "%llu\n", (unsigned long long)get_capacity(disk));
 }
-
+static ssize_t disk_capability_read(struct gendisk *disk, char *page)
+{
+        return sprintf(page, "%x\n", disk->flags);
+}
 static ssize_t disk_stats_read(struct gendisk * disk, char *page)
 {
         preempt_disable();
@@ -466,6 +469,10 @@ static struct disk_attribute disk_attr_size = {
         .attr = {.name = "size", .mode = S_IRUGO },
         .show   = disk_size_read
 };
+static struct disk_attribute disk_attr_capability = {
+        .attr = {.name = "capability", .mode = S_IRUGO },
+        .show   = disk_capability_read
+};
 static struct disk_attribute disk_attr_stat = {
         .attr = {.name = "stat", .mode = S_IRUGO },
         .show   = disk_stats_read
@@ -506,6 +513,7 @@ static struct attribute * default_attrs[] = {
         &disk_attr_removable.attr,
         &disk_attr_size.attr,
         &disk_attr_stat.attr,
+        &disk_attr_capability.attr,
 #ifdef CONFIG_FAIL_MAKE_REQUEST
         &disk_attr_fail.attr,
 #endif
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 4c03ee353e78..3fcfed2168a7 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -94,6 +94,7 @@ struct hd_struct {
 
 #define GENHD_FL_REMOVABLE                      1
 #define GENHD_FL_DRIVERFS                       2
+#define GENHD_FL_MEDIA_CHANGE_NOTIFY            4
 #define GENHD_FL_CD                             8
 #define GENHD_FL_UP                             16
 #define GENHD_FL_SUPPRESS_PARTITION_INFO        32