On Fri, Dec 12, 2014 at 3:12 PM, John Syn <[email protected]> wrote: > > On 12/11/14, 3:23 PM, "Robert Nelson" <[email protected]> wrote: > >>So if your watching git: >> >>https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id >>=7ef58b32f571bffb7763c6252ad7527562081f34 >> >>- OF_RECONFIG notifiers for SPI, I2C and Platform devices. Those >>subsystems can now respond to live changes to the device tree. >>- CONFIG_OF_OVERLAY method for applying live changes to the device tree > Yeah, this is really good news. BTW, what is the mechanism to update the > devicetree from user space? Is this done via sysfs like capemanager?
It's thru: "configfs", Pantelis's patch is here: http://www.spinics.net/lists/devicetree/msg61079.html <docs in patch> +Howto use the configfs overlay interface. + +A device-tree configfs entry is created in /config/device-tree/overlays +and and it is manipulated using standard file system I/O. +Note that this is a debug level interface, for use by developers and +not necessarily something accessed by normal users due to the +security implications of having direct access to the kernel's device tree. + +* To create an overlay you mkdir the directory: + + # mkdir /config/device-tree/overlays/foo + +* Either you echo the overlay firmware file to the path property file. + + # echo foo.dtbo >/config/device-tree/overlays/foo/path + +* Or you cat the contents of the overlay to the dtbo file + + # cat foo.dtbo >/config/device-tree/overlays/foo/dtbo + +The overlay file will be applied, and devices will be created/destroyed +as required. + +To remove it simply rmdir the directory. + + # rmdir /config/device-tree/overlays/foo + +The rationalle of the dual interface (firmware & direct copy) is that each is +better suited to different use patterns. The firmware interface is what's +intended to be used by hardware managers in the kernel, while the copy interface +make sense for developers (since it avoids problems with namespaces). Regards, -- Robert Nelson http://www.rcn-ee.com/ -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
