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Hi all,
Back in August I started a thread[1] on the cross-distro list at linaro on standardising the location of dtb files. While tehre was not a lot fo input there was a consensus to use /boot/dtb/ as the location. since the dtb generation is still tied to kernel building. I would like to have us have the most recently installed kernel link its dtb directory to /boot/dtb/ I am working on a change for Fedora 21 to get u-boot that we provide loading the dtb automatically and there is no way that ive worked out to have u-boot work out the path as they exist today.
I realise its not perfect and may cause issues if you try to boot an older kernel. I would like some feedback on how best to implement it so I can go off and write some patches for review.
Thanks in advance
Dennis
[1] http://lists.linaro.org/pipermail/cross-distro/2013-August/000463.html
On Wed, Dec 18, 2013 at 6:26 PM, Dennis Gilmore dennis@ausil.us wrote:
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Hi all,
Back in August I started a thread[1] on the cross-distro list at linaro on standardising the location of dtb files. While tehre was not a lot fo input there was a consensus to use /boot/dtb/ as the location. since the dtb generation is still tied to kernel building. I would like to have us have the most recently installed kernel link its dtb directory to /boot/dtb/ I am working on a change for Fedora 21 to get u-boot that we provide loading the dtb automatically and there is no way that ive worked out to have u-boot work out the path as they exist today.
Can you provide a little more context to those of us that don't have a clue as to what you're talking about?
Looking in koji, it seems the arm kernels install dtbs in:
/boot/dtb-{kver}.armv7hl/
Are you asking to have them installed in /boot/dtb/ instead? If so, wouldn't /boot/dtb/{kver}/ work, much like we do for modules in /lib/modules/{kver} ?
I'm not really understanding what you mean by "link its dtb directory to /boot/dtb/". If you mean making /boot/dtb a symlink to the dtb-{kver} directory on each kernel install, that seems a bit suboptimal. There's no guarantee that kernel will boot, or that the dtbs contained in the directory are working. Blindly changing the symlink seems wrong, plus there is a lot of headache on kernel uninstall to restore it to something (which might not be the previous kernel at install time).
josh
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El Wed, 18 Dec 2013 18:36:27 -0500 Josh Boyer jwboyer@gmail.com escribió:
On Wed, Dec 18, 2013 at 6:26 PM, Dennis Gilmore dennis@ausil.us wrote:
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Hi all,
Back in August I started a thread[1] on the cross-distro list at linaro on standardising the location of dtb files. While tehre was not a lot fo input there was a consensus to use /boot/dtb/ as the location. since the dtb generation is still tied to kernel building. I would like to have us have the most recently installed kernel link its dtb directory to /boot/dtb/ I am working on a change for Fedora 21 to get u-boot that we provide loading the dtb automatically and there is no way that ive worked out to have u-boot work out the path as they exist today.
Can you provide a little more context to those of us that don't have a clue as to what you're talking about?
Looking in koji, it seems the arm kernels install dtbs in:
/boot/dtb-{kver}.armv7hl/
Are you asking to have them installed in /boot/dtb/ instead? If so, wouldn't /boot/dtb/{kver}/ work, much like we do for modules in /lib/modules/{kver} ?
I'm not really understanding what you mean by "link its dtb directory to /boot/dtb/". If you mean making /boot/dtb a symlink to the dtb-{kver} directory on each kernel install, that seems a bit suboptimal. There's no guarantee that kernel will boot, or that the dtbs contained in the directory are working. Blindly changing the symlink seems wrong, plus there is a lot of headache on kernel uninstall to restore it to something (which might not be the previous kernel at install time).
I need to hard code into u-boot a set of locations to try and load the dtb from i.e. /boot/dtb/ /dtb/
bootcmd_disk=load ${boot_ifc} ${bootdevice} ${fdt_addr} /boot/dtb/${fdt_file}; load ${boot_ifc} ${bootdevice} ${fdt_addr} /dtb/${fdt_file};run bootcmd_disk_sysboot1; run bootcmd_disk_sysboot2;
${fdt_file} is a variable inside of u-boot that defines the dtb file to load.
I want to make /boot/dtb a symlink to the dtb-{kver} directory. I realise that its not really perfect until the kernel defines them as an ABI which seems to be the long term goal. In practice there has been a few times where you can not mix and match dtb and kernels. high bank for instance has a dtb built from 3.10 i think, there was a point a firmware update was needed toreplace the dtb because of an incompatability. in the f20 cycle i used the 3.12 dtb with 3.11 on my wandboard quad because it enabled more hardware support.
at some future date I expect that the dtbs will be detached from the kernel and packaged up separately. at which point things would be just fine. Maybe we should preempt that and split off the building of them today, either by having a kernel-dtb sub package, or pulling them out into their own package completely.
The other way to deal with it is much more invasive. It would mean adding a fdt line in extlinux.conf pointing at the dtb for the specific board and writing something so anaconda can work out when and how to add a fdt line, its not needed on some devices but would be needed on others. grubby would need some patching to update the fdt line correctly.
Dennis
On Wed, Dec 18, 2013 at 7:23 PM, Dennis Gilmore dennis@ausil.us wrote:
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El Wed, 18 Dec 2013 18:36:27 -0500 Josh Boyer jwboyer@gmail.com escribió:
On Wed, Dec 18, 2013 at 6:26 PM, Dennis Gilmore dennis@ausil.us wrote:
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1
Hi all,
Back in August I started a thread[1] on the cross-distro list at linaro on standardising the location of dtb files. While tehre was not a lot fo input there was a consensus to use /boot/dtb/ as the location. since the dtb generation is still tied to kernel building. I would like to have us have the most recently installed kernel link its dtb directory to /boot/dtb/ I am working on a change for Fedora 21 to get u-boot that we provide loading the dtb automatically and there is no way that ive worked out to have u-boot work out the path as they exist today.
Can you provide a little more context to those of us that don't have a clue as to what you're talking about?
Looking in koji, it seems the arm kernels install dtbs in:
/boot/dtb-{kver}.armv7hl/
Are you asking to have them installed in /boot/dtb/ instead? If so, wouldn't /boot/dtb/{kver}/ work, much like we do for modules in /lib/modules/{kver} ?
I'm not really understanding what you mean by "link its dtb directory to /boot/dtb/". If you mean making /boot/dtb a symlink to the dtb-{kver} directory on each kernel install, that seems a bit suboptimal. There's no guarantee that kernel will boot, or that the dtbs contained in the directory are working. Blindly changing the symlink seems wrong, plus there is a lot of headache on kernel uninstall to restore it to something (which might not be the previous kernel at install time).
I need to hard code into u-boot a set of locations to try and load the dtb from i.e. /boot/dtb/ /dtb/
bootcmd_disk=load ${boot_ifc} ${bootdevice} ${fdt_addr} /boot/dtb/${fdt_file}; load ${boot_ifc} ${bootdevice} ${fdt_addr} /dtb/${fdt_file};run bootcmd_disk_sysboot1; run bootcmd_disk_sysboot2;
${fdt_file} is a variable inside of u-boot that defines the dtb file to load.
I want to make /boot/dtb a symlink to the dtb-{kver} directory. I realise that its not really perfect until the kernel defines them as an ABI which seems to be the long term goal. In practice there has been a few times where you can not mix and match dtb and kernels. high bank for instance has a dtb built from 3.10 i think, there was a point a firmware update was needed toreplace the dtb because of an incompatability. in the f20 cycle i used the 3.12 dtb with 3.11 on my wandboard quad because it enabled more hardware support.
It would be rather difficult to do that sanely from a packaging perspective. You can blindly move the symlink on install, but what do you do on uninstall? You're basically left with leaving it alone entirely because you have nothing to really determine what to point it back to. Which means you could wind up with a broken link if you try to boot a kernel and it fails and then you uninstall that kernel.
at some future date I expect that the dtbs will be detached from the kernel and packaged up separately. at which point things would be just fine. Maybe we should preempt that and split off the building of them today, either by having a kernel-dtb sub package, or pulling them out into their own package completely.
Splitting it out is probably the best way forward. I'd suggest building them in u-boot itself if you don't want to hassle with a separate package, given that it is the thing that has the dependency.
The other way to deal with it is much more invasive. It would mean adding a fdt line in extlinux.conf pointing at the dtb for the specific board and writing something so anaconda can work out when and how to add a fdt line, its not needed on some devices but would be needed on others. grubby would need some patching to update the fdt line correctly.
If splitting it out isn't feasible, then fixing the bootloader scripts might be the second best solution. It's more work overall, but the correct solution isn't always the easiest.
josh
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Josh Boyer