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On Tue, 6 Aug 2013 11:53:02 +0800 Andy Green andy.green@linaro.org 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).
/boot/dtb/ is the directory that contains all the dtbs. omap and other platforms, have a findfdt function that will tell you the expeted dtb filename for the board. we just need to put them in a know location.
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.
depending on the system you would need to update the u-boot installed into the card, a scriptable task, or ensure that the installed u-boot has the unified features needed. but I fully expect that it something people can and will want to do.
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.
I hope the long term outcome here is that u-boot or any other bootloader would be able to know where to find the dtb file regardless of distro because we all honour and do the same thing.
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.
They exist today in fedora, as of Fedora 19 we are shipping a multiplatform kernel. The same images can run on multiple boards. I don't want to limit what systems are supported in any way. but come up with a flexible portable setup.
Dennis