Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+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
+interfaces 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.