On Mon, Jan 31, 2011 at 3:01 PM, Grant Likely <grant.lik...@secretlab.ca> wrote: > This patch implements an alternate method for using device tree data > for populating machine device registration. Traditionally, board > support has directly generated and registered devices based on nodes > in the device tree. The board support code starts at the root of the > tree and begins allocating devices for each device node it finds. > Similarly, bus drivers (i2c, spi, etc.) use their child nodes to > register child devices. This model can be seen in almost all the powerpc > board ports (arch/powerpc/platforms/*). > > However, for many of the ARM SoCs, there already exists complete board > support for many SoCs that have their own code for registering the > basic set of platform devices with non-trivial dependencies on clock > structure and machine specific platform code. While starting at the > base of the tree and working up is certainly possible, it requires > modifying a lot of machine support code to get it working. > > Instead, this patch provides an alternate approach. Instead of > starting at the root of the tree and working up, this patch allows the > SoC support code to register its standard set of platform devices in > the normal way. However, it also registers a platform_bus notifier > function which compares platform_device registrations with data in the > device tree. Whenever it finds a matching node, it increments the > node reference count and assigns it to the device's of_node pointer so > that it is available for the device driver to use and bind against. > For example, an spi master driver would have access to the spi node > which contains information about all the spi slaves on the bus.
One more note. It might also be a good idea to do something like this for the PCI and AMBA buses. I've not yet looked at how much code could be made common for implementing that. g. _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
