Messages in this thread | | | From | Marc Zyngier <> | Subject | [RFC PATCH v2 0/4] Core device subsystem | Date | Fri, 8 Jul 2011 09:54:06 +0100 |
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There is a small number of devices that the core kernel needs very early in the boot process, namely an interrupt controller and a timer, long before the driver model is up and running.
Most architectures implement this requirement by hardcoding the initialisation of a "well known" piece of hardware which is standard enough to work on any platform.
This is very different on the ARM architecture, where platforms have a variety of interrupt controllers and timers. While the same hardcoding is possible (and is actually used), it makes it almost impossible to support several platforms in the same kernel.
Though the device tree is helping greatly to solve this problem, some platform won't ever be converted to DT, hence the need to have a mechanism supporting a variety of information source. Early platform devices having been deemed unsuitable (complexity, abuse of various subsystems), this subsystem has been designed to provide the very minimal level of functionality.
The "core device subsystem" offers a class based device/driver matching model, doesn't rely on any other subsystem, is very (too?) simple, and support getting information both from DT as well as from static data provided by the platform. It also gives the opportunity to define the probing order by offering a sorting hook at run-time.
As for the Linux driver model, the core device subsystem deals mainly with device and driver objects. It also has the notion of "class" to designate a group of devices implementing the same functionality, and a group of drivers to be matched against the above devices (CORE_DEV_CLASS_TIMER for example).
Tested on RealView PB-11MP (with both dt and non dt setups), and Samsug SMDKv310 (non-dt only).
From v1 (never posted): - Interrupt controller sort function - Bug fixes - Added documentation
Marc Zyngier (4): dt: expose device resource allocator Core device subsystem implementation Core devices: add OF interrupt controller sorting method Core devices: documentation
Documentation/core_devices.txt | 247 +++++++++++++++++++++++++++++++++++++ arch/arm/kernel/vmlinux.lds.S | 1 + drivers/base/Makefile | 3 +- drivers/base/core_device.c | 217 ++++++++++++++++++++++++++++++++ drivers/of/platform.c | 60 ++++++--- include/asm-generic/vmlinux.lds.h | 6 + include/linux/core_device.h | 71 +++++++++++ include/linux/of_platform.h | 2 + 8 files changed, 587 insertions(+), 20 deletions(-) create mode 100644 Documentation/core_devices.txt create mode 100644 drivers/base/core_device.c create mode 100644 include/linux/core_device.h
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