[SCSI] embryonic RAID class

The idea behind a RAID class is to provide a uniform interface to all
RAID subsystems (both hardware and software) in the kernel.

To do that, I've made this class a transport class that's entirely
subsystem independent (although the matching routines have to match per
subsystem, as you'll see looking at the code).  I put it in the scsi
subdirectory purely because I needed somewhere to play with it, but it's
not a scsi specific module.

I used a fusion raid card as the test bed for this; with that kind of
card, this is the type of class output you get:

jejb@titanic> ls -l /sys/class/raid_devices/20\:0\:0\:0/
total 0
lrwxrwxrwx  1 root root     0 Aug 16 17:21 component-0 -> ../../../devices/pci0000:80/0000:80:04.0/host20/target20:1:0/20:1:0:0/
lrwxrwxrwx  1 root root     0 Aug 16 17:21 component-1 -> ../../../devices/pci0000:80/0000:80:04.0/host20/target20:1:1/20:1:1:0/
lrwxrwxrwx  1 root root     0 Aug 16 17:21 device -> ../../../devices/pci0000:80/0000:80:04.0/host20/target20:0:0/20:0:0:0/
-r--r--r--  1 root root 16384 Aug 16 17:21 level
-r--r--r--  1 root root 16384 Aug 16 17:21 resync
-r--r--r--  1 root root 16384 Aug 16 17:21 state

So it's really simple: for a SCSI device representing a hardware raid,
it shows the raid level, the array state, the resync % complete (if the
state is resyncing) and the underlying components of the RAID (these are
exposed in fusion on the virtual channel 1).

As you can see, this type of information can be exported by almost
anything, including software raid.

The more difficult trick, of course, is going to be getting it to
perform configuration type actions with writable attributes.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/include/linux/raid_class.h b/include/linux/raid_class.h
new file mode 100644
index 000000000000..a71123c28272
--- /dev/null
+++ b/include/linux/raid_class.h
@@ -0,0 +1,59 @@
+/*
+ */
+#include <linux/transport_class.h>
+
+struct raid_template {
+        struct transport_container raid_attrs;
+};
+
+struct raid_function_template {
+        void *cookie;
+        int (*is_raid)(struct device *);
+        void (*get_resync)(struct device *);
+        void (*get_state)(struct device *);
+};
+
+enum raid_state {
+        RAID_ACTIVE = 1,
+        RAID_DEGRADED,
+        RAID_RESYNCING,
+        RAID_OFFLINE,
+};
+
+struct raid_data {
+        struct list_head component_list;
+        int component_count;
+        int level;
+        enum raid_state state;
+        int resync;
+};
+
+#define DEFINE_RAID_ATTRIBUTE(type, attr)                                     \
+static inline void                                                            \
+raid_set_##attr(struct raid_template *r, struct device *dev, type value) {    \
+        struct class_device *cdev =                                           \
+                attribute_container_find_class_device(&r->raid_attrs.ac, dev);\
+        struct raid_data *rd;                                                 \
+        BUG_ON(!cdev);                                                        \
+        rd = class_get_devdata(cdev);                                         \
+        rd->attr = value;                                                     \
+}                                                                             \
+static inline type                                                            \
+raid_get_##attr(struct raid_template *r, struct device *dev) {                \
+        struct class_device *cdev =                                           \
+                attribute_container_find_class_device(&r->raid_attrs.ac, dev);\
+        struct raid_data *rd;                                                 \
+        BUG_ON(!cdev);                                                        \
+        rd = class_get_devdata(cdev);                                         \
+        return rd->attr;                                                      \
+}
+
+DEFINE_RAID_ATTRIBUTE(int, level)
+DEFINE_RAID_ATTRIBUTE(int, resync)
+DEFINE_RAID_ATTRIBUTE(enum raid_state, state)
+        
+struct raid_template *raid_class_attach(struct raid_function_template *);
+void raid_class_release(struct raid_template *);
+
+void raid_component_add(struct raid_template *, struct device *,
+                        struct device *);