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? > > Let me know what you think, > Maxime > > Changes from v2: > - Add Kconfig option for the libfdt overlay support > - Reworked the code to deal with Pantelis and David numerous > comments, among which: > * Remove the need for malloc in the overlay code, and added some > libfdt functions to do that > * Remove the DT magic in case of an error to not be able to use it > anymore > * Removed the fdt_ and _ function prefix for the static functions > * Plus the usual bunch of rework, error checking and optimizations. > > - Added new tests to deal with bugs reported by David (the overlay > was not applying when you add a subnode declared that was already > in the base device tree, and using a local phandle was only > working if the property storing it only had a length of 4). > > Changes from v1: > - Moved the overlay code to libfdt > - Added unit tests > - Refactored the code to reduce the amount of memory allocation > - No longer modify the overlay itself, but create a copy to operate > on instead. > - Removed the limitations on the fixups path, names and properties > length > - Fixed a few things here and there according to comments > > Maxime Ripard (12): > cmd: fdt: Narrow the check for fdt addr > scripts: Makefile.lib: Sanitize DTB names > vsprintf: Include stdarg for va_list > libfdt: Add new headers and defines > libfdt: Add iterator over properties > libfdt: Add max phandle retrieval function > libfdt: Add fdt_setprop_inplace_by_index > libfdt: Add fdt_path_offset_namelen > libfdt: Add fdt_getprop_namelen_w > libfdt: Add overlay application function > cmd: fdt: add fdt overlay application subcommand > tests: Introduce DT overlay tests > > Makefile | 1 + > cmd/fdt.c | 26 ++- > include/libfdt.h | 124 ++++++++++++- > include/libfdt_env.h | 6 + > include/test/overlay.h | 16 ++ > include/test/suites.h | 1 + > include/vsprintf.h | 2 + > lib/Kconfig | 5 + > lib/libfdt/Makefile | 2 + > lib/libfdt/fdt_overlay.c | 381 ++++++++++++++++++++++++++++++++++++++ > lib/libfdt/fdt_ro.c | 44 ++++- > lib/libfdt/fdt_wip.c | 13 +- > scripts/Makefile.lib | 8 +- > test/Kconfig | 1 + > test/cmd_ut.c | 6 + > test/overlay/Kconfig | 11 ++ > test/overlay/Makefile | 15 ++ > test/overlay/cmd_ut_overlay.c | 243 ++++++++++++++++++++++++ > test/overlay/test-fdt-base.dts | 21 +++ > test/overlay/test-fdt-overlay.dts | 88 +++++++++ > 20 files changed, 992 insertions(+), 22 deletions(-) > create mode 100644 include/test/overlay.h > create mode 100644 lib/libfdt/fdt_overlay.c > create mode 100644 test/overlay/Kconfig > create mode 100644 test/overlay/Makefile > create mode 100644 test/overlay/cmd_ut_overlay.c > create mode 100644 test/overlay/test-fdt-base.dts > create mode 100644 test/overlay/test-fdt-overlay.dts > -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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