Hi David, On Mon, Jun 27, 2016 at 01:37:19AM +1000, David Gibson wrote: > On Fri, Jun 24, 2016 at 04:27:45PM +0200, Maxime Ripard wrote: > > Hi, > > > > The device tree overlays are a great solution to the issue raised by > > the bunch expandable boards we find everywhere these days, like the > > Beaglebone, Raspberry Pi or CHIP. > > > > However, most of the time, the overlays are applied through a > > mechanism involving the firmware request interface in Linux, that is > > only fully functional once the userspace has been mounted and is > > running. > > > > Some expansion boards might need to be enabled before that, because > > they simply need to patch the DT early on, or need to be initialized > > early in order to be fully functional, or because they provide access > > to the root filesystem. > > > > In these cases, having the bootloader applying the overlay before > > Linux starts seems like the easiest solution. > > > > This implementation doesn't provide all the Linux fancyness though, > > there's no transactional application, which means that if the overlay > > cannot be applied for a reason while you're still halfway through the > > application, you're probably screwed. It also cannot remove an > > overlay, but I don't think that it is currently a use-case. > > > > There's still a bunch of work to extend the libfdt unit tests to test > > the new functions introduced, but these patches will be submitted > > in a near future. > > Are you planning to send a new version of (the relevant portions of) > these against upstream libfdt? Of course, I just only have to work on the test cases now. Simon wanted to merge this in U-Boot for the next merge window, and then sync with libfdt when it would be merged, hence why I posted it first. Maxime -- Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com
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