Hi Simon
Le mer. 13 oct. 2021 à 03:35, Tom Rini <tr...@konsulko.com> a écrit : > On Wed, Oct 13, 2021 at 09:29:14AM +0800, Bin Meng wrote: > > Hi Simon, > > > > On Wed, Oct 13, 2021 at 9:01 AM Simon Glass <s...@chromium.org> wrote: > > > > > > With Ilias' efforts we have dropped OF_PRIOR_STAGE and OF_HOSTFILE so > > > there are only three ways to obtain a devicetree: > > > > > > - OF_SEPARATE - the normal way, where the devicetree is built and > > > appended to U-Boot > > > - OF_EMBED - for development purposes, the devicetree is embedded in > > > the ELF file (also used for EFI) > > > - OF_BOARD - the board figures it out on its own > > > > > > The last one is currently set up so that no devicetree is needed at all > > > in the U-Boot tree. Most boards do provide one, but some don't. Some > > > don't even provide instructions on how to boot on the board. > > > > > > The problems with this approach are documented at [1]. > > > > > > In practice, OF_BOARD is not really distinct from OF_SEPARATE. Any > board > > > can obtain its devicetree at runtime, even it is has a devicetree built > > > in U-Boot. This is because U-Boot may be a second-stage bootloader and > its > > > caller may have a better idea about the hardware available in the > machine. > > > This is the case with a few QEMU boards, for example. > > > > > > So it makes no sense to have OF_BOARD as a 'choice'. It should be an > > > option, available with either OF_SEPARATE or OF_EMBED. > > > > > > This series makes this change, adding various missing devicetree files > > > (and placeholders) to make the build work. > > > > Adding device trees that are never used sounds like a hack to me. > > > > For QEMU, device tree is dynamically generated on the fly based on > > command line parameters, and the device tree you put in this series > > has various hardcoded <phandle> values which normally do not show up > > in hand-written dts files. > > > > I am not sure I understand the whole point of this. > > I am also confused and do not like the idea of adding device trees for > platforms that are capable of and can / do have a device tree to give us > at run time. > > -- > Tom +1 While the cleanup go get three options, including OF_BOARD is nice, the build solution you propose does not sound the right approach: U-Boot should be buildable without any DT. Getting the DT you produced as sample information can be useful and kept out of build path in documentation with ad-hoc warnings though as I explained in other mails of the series. OF_BOARD is a choice to say “I don’t override the legitimate DT with either OF_SEPARATE or OF_EMBED” (which I see in this case as debug facility for U-Boot maintainer of the platform). > > -- François-Frédéric Ozog | *Director Business Development* T: +33.67221.6485 francois.o...@linaro.org | Skype: ffozog
