On 6 August 2013 20:53, Rob Herring robherring2@gmail.com wrote:
On 08/05/2013 10:53 PM, Andy Green wrote:
On 6 August 2013 11:05, Rob Herring robherring2@gmail.com wrote:
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On 08/05/2013 04:41 PM, Dennis Gilmore wrote:
Hi all,
As part of the unified features in u-boot thread I said that I would work to get distros to agree to a common location that u-boot will be able to assume exists for it to transparently load dtbs from for us.
I would like to propose /boot/dtb/
I think it needs to be in /boot/ to allow for booting from systems with / and /boot on separate partitions. I believe Ubuntu and hence Debian put them in /lib somewhere today. Fedora puts them in /boot/dtb-<kernel version>. im not sure where the other distros put them.
A DTB should not be tied to a kernel version. I realize that is a reality for some boards, but lets not encourage that. There are also plans to remove dts files from the kernel.
I think that until they are decoupled from the kernel Fedora would have /boot/dtb be a symlink to the latest installed kernel. once its decoupled it would be the location where the dtbs are installed.
If /boot/dtb is THE dtb to use, does more than that need to be specified (at least from a bootloader perspective).
If I understood you correctly, that'd be needlessly limiting one image to one board.
Consider an SD Card + CONFIG_ARCH_MULTIPLATFORM kernel you can pull out and plug in to use on a variety of different boards, the bootloader would need to identify the correct dtb and pass it to the kernel.
Ah, right. I misread this.
So do we assume the dtb file names are known by the bootloader for a board or standardized in some way?
Yes it has to be like that, something has to pick a dtb one way or another and give it to the kernel.
It can be because that's the only dtb on the image and that's all it can deal with, but hopefully in the future the bootloader will absorb some of the ARCH_MULTIPLATFORM thinking from the kernel and not be limited by single compile-time platform choice any more, and support many possible platforms and select the correct dtb.
It doesn't hurt if it's a directory with one thing in for the first case, and doing that enables the second case, so it seems the right way.
-Andy
Rob
U-Boot is bound up with compile-time decisions about targeting a single board at the moment, but if we're talking about long term decisions like /boot/dtb/ just like ARM isn't the only consideration U-Boot is not the only bootloader.
Once kernels capable of running a single binary on many platforms are common (they're already workable) pressure for the bootloader to do likewise will increase. So it'd be a shame to block that by choosing a dtb convention that assumes there's only one on the image.
-Andy