Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 70 insertions, 0 deletions

diff --git a/Documentation/scsi/megaraid.txt b/Documentation/scsi/megaraid.txt
new file mode 100644
index 000000000000..ff864c0f494c
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+++ b/Documentation/scsi/megaraid.txt
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+			Notes on Management Module
+			~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Overview:
+--------
+
+Different classes of controllers from LSI Logic, accept and respond to the
+user applications in a similar way. They understand the same firmware control
+commands. Furthermore, the applications also can treat different classes of
+the controllers uniformly. Hence it is logical to have a single module that
+interefaces with the applications on one side and all the low level drivers
+on the other.
+
+The advantages, though obvious, are listed for completeness:
+
+	i.	Avoid duplicate code from the low level drivers.
+	ii.	Unburden the low level drivers from having to export the
+		character node device and related handling.
+	iii.	Implement any policy mechanisms in one place.
+	iv.	Applications have to interface with only module instead of
+		multiple low level drivers.
+
+Currently this module (called Common Management Module) is used only to issue
+ioctl commands. But this module is envisioned to handle all user space level
+interactions. So any 'proc', 'sysfs' implementations will be localized in this
+common module.
+
+Credits:
+-------
+
+"Shared code in a third module, a "library module", is an acceptable
+solution. modprobe automatically loads dependent modules, so users
+running "modprobe driver1" or "modprobe driver2" would automatically
+load the shared library module."
+
+		- Jeff Garzik (jgarzik@pobox.com), 02.25.2004 LKML
+
+"As Jeff hinted, if your userspace<->driver API is consistent between
+your new MPT-based RAID controllers and your existing megaraid driver,
+then perhaps you need a single small helper module (lsiioctl or some
+better name), loaded by both mptraid and megaraid automatically, which
+handles registering the /dev/megaraid node dynamically. In this case,
+both mptraid and megaraid would register with lsiioctl for each
+adapter discovered, and lsiioctl would essentially be a switch,
+redirecting userspace tool ioctls to the appropriate driver."
+
+		- Matt Domsch, (Matt_Domsch@dell.com), 02.25.2004 LKML
+
+Design:
+------
+
+The Common Management Module is implemented in megaraid_mm.[ch] files. This
+module acts as a registry for low level hba drivers. The low level drivers
+(currently only megaraid) register each controller with the common module.
+
+The applications interface with the common module via the character device
+node exported by the module.
+
+The lower level drivers now understand only a new improved ioctl packet called
+uioc_t. The management module converts the older ioctl packets from the older
+applications into uioc_t. After driver handles the uioc_t, the common module
+will convert that back into the old format before returning to applications.
+
+As new applications evolve and replace the old ones, the old packet format 
+will be retired.
+
+Common module dedicates one uioc_t packet to each controller registered. This
+can easily be more than one. But since megaraid is the only low level driver
+today, and it can handle only one ioctl, there is no reason to have more. But
+as new controller classes get added, this will be tuned appropriately.