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.

James

@@ -1,5 +1,11 @@
 menu "SCSI device support"
 
+config RAID_ATTRS
+	tristate "RAID Transport Class"
+	default n
+	---help---
+	  Provides RAID
+
 config SCSI
 	tristate "SCSI device support"
 	---help---

@@ -22,6 +22,8 @@ subdir-$(CONFIG_PCMCIA)		+= pcmcia
 
 obj-$(CONFIG_SCSI)		+= scsi_mod.o
 
+obj-$(CONFIG_RAID_ATTRS)	+= raid_class.o
+
 # --- NOTE ORDERING HERE ---
 # For kernel non-modular link, transport attributes need to
 # be initialised before drivers