[U-Boot] [PATCH 00/19] fdt: Move to the new upstream pylibfdt library

[Simon Glass]

Hi,

On 19 April 2017 at 08:27, Tom Rini <trini at konsulko.com> wrote:
> On Tue, Apr 18, 2017 at 10:48:07AM -0600, Simon Glass wrote:
>> Hi Tom,
>>
>> On 18 April 2017 at 10:33, Tom Rini <trini at konsulko.com> wrote:
>> > On Tue, Apr 18, 2017 at 10:27:37AM -0600, Simon Glass wrote:
>> >> Hi Tom,
>> >>
>> >> On 18 April 2017 at 10:25, Tom Rini <trini at konsulko.com> wrote:
>> >> >
>> >> > On Sun, Apr 16, 2017 at 08:22:14PM -0600, Simon Glass wrote:
>> >> >
>> >> > > Python libfdt bindings have recently been accepted upstream. While the
>> >> > > internals have changed a fair bit most of the API remains the same. Still,
>> >> > > a few functions are different from how they are used in U-Boot so changes
>> >> > > are needed to make this work.
>> >> > >
>> >> > > At present in U-Boot there are two libraries for accessing a device tree
>> >> > > file:
>> >> > >
>> >> > > - FdtNormal which uses U-Boot's own Python bindings
>> >> > > - FdtFallback which uses the fdtget command-line utility
>> >> > >
>> >> > > The latter is not a great solution: it is fairly slow since the DT is
>> >> > > re-read for every access and it cannot provide DT offsets or packing of
>> >> > > the DT.
>> >> > >
>> >> > > In addition, U-Boot now builds the libfdt module if swig is available,
>> >> > > meaning that the fallback module is not used in that case.
>> >> > >
>> >> > > Finally, at some point in the future distributions may start packaging the
>> >> > > libfdt Python module and it will be available without U-Boot needing to
>> >> > > build it itself.
>> >> > >
>> >> > > Therefore it seems like a good idea to take this opportunity to drop the
>> >> > > fallback module and just require that the Python libfdt bindings be
>> >> > > present (at least if need by the build).
>> >> > >
>> >> > > The bindings are needed in two situations:
>> >> > > - When dtoc is used to convert a device tree into C code. This is enabled
>> >> > >     by CONFIG_SPL_OF_PLATDATA
>> >> > > - When binman is used to produce a firmware image. This is used on all x86
>> >> > >     and sunxi boards at present
>> >> > >
>> >> > > This series:
>> >> > > - Plumbs in building the Python libfdt module to the U-Boot build system
>> >> > > - Ensures that the module is always built if needed, print an error if
>> >> > >     swig is not available (and thus the module cannot be built)
>> >> > > - Allows use of a libfdt.py module already installed on the machine
>> >> > > - Drops the FdtFallback support
>> >> > > - Moves fdt.h and libfdt.h into lib/libfdt to aid with syncing with
>> >> > >     upstream, building the Python bindings and to keep the code together
>> >> > > - Merges Fdt and FdtNormal to simplify the code
>> >> > > - Adjusts the Fdt library to work with the new libfdt module
>> >> > > - Adds a few more tests to check access to properties in the DT
>> >> > > - Adjusts binman and dtoc to work with the new approach
>> >> > >
>> >> > > It should be possible to easily sync libfdt's Python bindings with U-Boot
>> >> > > in the future, as development there proceeds.
>> >> >
>> >> > While this came in late, my gut feeling is that it would be best to have
>> >> > this change in the next release (so that various upstreams can get used
>> >> > to the idea of basically always needing python installed to build).
>> >>
>> >> I'm a little worried that it might cause problems. I made it so that
>> >> it only *requires* python if is it actually needed, though it always
>> >> builds libfdt.py if it can. Or perhaps that is what you are saying,
>> >> that the only way to flush out upstream issues is to apply it?
>> >
>> > What I'm saying is that distros (Fedora, openSUSE, OpenEmbedded) are
>> > going to make a blanket change (if they haven't already) to say that
>> > building U-Boot requires python to be installed (since they aren't
>> > likely to try and optimize it on a board-by-board basis when it's "easy"
>> > to just say it's an always dependency).  If you think there's risk with
>> > the change itself, we can wait a release, that's fine too.  Thanks!
>>
>> I see. I'm not sure what is best. I checked for build errors and added
>> some more tests so I'm fairly confident. But it is late (sorry, it was
>> more work than I expected). I'll leave this up to you.
>
> Alright, lets just have this queued up for early next window.

I've pushed this to u-boot-fdt/next. If anyone has time to test that
this builds OK (particularly 'buildman sandbox') it would be
appreciated.

Regards,
Simon