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- Notes on Management Module
- ~~~~~~~~~~~~~~~~~~~~~~~~~~
-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.
-"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 (, 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, (, 02.25.2004 LKML
-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.