Based on kernel version 4.3. Page generated on 2015-11-02 12:51 EST.
1 Notes on Management Module 2 ~~~~~~~~~~~~~~~~~~~~~~~~~~ 3 4 Overview: 5 -------- 6 7 Different classes of controllers from LSI Logic accept and respond to the 8 user applications in a similar way. They understand the same firmware control 9 commands. Furthermore, the applications also can treat different classes of 10 the controllers uniformly. Hence it is logical to have a single module that 11 interfaces with the applications on one side and all the low level drivers 12 on the other. 13 14 The advantages, though obvious, are listed for completeness: 15 16 i. Avoid duplicate code from the low level drivers. 17 ii. Unburden the low level drivers from having to export the 18 character node device and related handling. 19 iii. Implement any policy mechanisms in one place. 20 iv. Applications have to interface with only module instead of 21 multiple low level drivers. 22 23 Currently this module (called Common Management Module) is used only to issue 24 ioctl commands. But this module is envisioned to handle all user space level 25 interactions. So any 'proc', 'sysfs' implementations will be localized in this 26 common module. 27 28 Credits: 29 ------- 30 31 "Shared code in a third module, a "library module", is an acceptable 32 solution. modprobe automatically loads dependent modules, so users 33 running "modprobe driver1" or "modprobe driver2" would automatically 34 load the shared library module." 35 36 - Jeff Garzik (email@example.com), 02.25.2004 LKML 37 38 "As Jeff hinted, if your userspace<->driver API is consistent between 39 your new MPT-based RAID controllers and your existing megaraid driver, 40 then perhaps you need a single small helper module (lsiioctl or some 41 better name), loaded by both mptraid and megaraid automatically, which 42 handles registering the /dev/megaraid node dynamically. In this case, 43 both mptraid and megaraid would register with lsiioctl for each 44 adapter discovered, and lsiioctl would essentially be a switch, 45 redirecting userspace tool ioctls to the appropriate driver." 46 47 - Matt Domsch, (Matt_Domsch@dell.com), 02.25.2004 LKML 48 49 Design: 50 ------ 51 52 The Common Management Module is implemented in megaraid_mm.[ch] files. This 53 module acts as a registry for low level hba drivers. The low level drivers 54 (currently only megaraid) register each controller with the common module. 55 56 The applications interface with the common module via the character device 57 node exported by the module. 58 59 The lower level drivers now understand only a new improved ioctl packet called 60 uioc_t. The management module converts the older ioctl packets from the older 61 applications into uioc_t. After driver handles the uioc_t, the common module 62 will convert that back into the old format before returning to applications. 63 64 As new applications evolve and replace the old ones, the old packet format 65 will be retired. 66 67 Common module dedicates one uioc_t packet to each controller registered. This 68 can easily be more than one. But since megaraid is the only low level driver 69 today, and it can handle only one ioctl, there is no reason to have more. But 70 as new controller classes get added, this will be tuned appropriately.