Modifying device-tree: /chosen

Modifying device-tree: /chosen

[Baeuerle, Florian]

Hi,

I haven't found a (good) way to modify the kernel device tree before booting
when using the bootchooser in combination with blspec.  What seems to be done
quite often is registering fixup functions (of_register_fixup) in board-specific
code.

I'd prefer not patch board-specific code, because my use case is rather specific
(passing the device serial number, the bootloader version, and a few other
things to the kernel). So the question is, if this use case is common enough to
provide a more generic way.

My proposal is providing a command like this:

of_fixup_chosen [PROPERTY] [VALUE]

I guess it would suffice to only store strings in /chosen.

Example:
of_fixup_chosen bootloader-version $global.version 
of_fixup_chosen reset-reason $global.system.reset
of_fixup_chosen serial $serial_number


I'm open for other suggestions, as this could also be implementend in a more
generic (and also more complex) way by allowing to fix up random nodes and
properties throughout the device tree.


Best Regards
Florian
_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox

Re: Modifying device-tree: /chosen

[Pascal Vizeli]

Maybe we can also include the:
http://lists.infradead.org/pipermail/barebox/2015-March/022708.html

It would be nice to use feature like this to modify the device tree
before we boot the kernel.

Pascal

2018-05-23 12:59 GMT+02:00 Baeuerle, Florian <Florian.Baeuerle@allegion.com>:
> Hi,
>
> I haven't found a (good) way to modify the kernel device tree before booting
> when using the bootchooser in combination with blspec.  What seems to be done
> quite often is registering fixup functions (of_register_fixup) in board-specific
> code.
>
> I'd prefer not patch board-specific code, because my use case is rather specific
> (passing the device serial number, the bootloader version, and a few other
> things to the kernel). So the question is, if this use case is common enough to
> provide a more generic way.
>
> My proposal is providing a command like this:
>
> of_fixup_chosen [PROPERTY] [VALUE]
>
> I guess it would suffice to only store strings in /chosen.
>
> Example:
> of_fixup_chosen bootloader-version $global.version
> of_fixup_chosen reset-reason $global.system.reset
> of_fixup_chosen serial $serial_number
>
>
> I'm open for other suggestions, as this could also be implementend in a more
> generic (and also more complex) way by allowing to fix up random nodes and
> properties throughout the device tree.
>
>
> Best Regards
> Florian
> _______________________________________________
> barebox mailing list
> barebox@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/barebox

_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox

Re: Modifying device-tree: /chosen

[Sascha Hauer]

Hi Florian,

On Wed, May 23, 2018 at 10:59:21AM +0000, Baeuerle, Florian wrote:
> Hi,
> 
> I haven't found a (good) way to modify the kernel device tree before booting
> when using the bootchooser in combination with blspec.  What seems to be done
> quite often is registering fixup functions (of_register_fixup) in board-specific
> code.
> 
> I'd prefer not patch board-specific code, because my use case is rather specific
> (passing the device serial number, the bootloader version, and a few other
> things to the kernel). So the question is, if this use case is common enough to
> provide a more generic way.
> 
> My proposal is providing a command like this:
> 
> of_fixup_chosen [PROPERTY] [VALUE]

This seems to be very similar to what I suggested here:

https://www.spinics.net/lists/u-boot-v2/msg32661.html

I see no reason to limit this command to the /chosen node, we could
equally well accept a full path to the node rather than just a property
name.

> 
> I guess it would suffice to only store strings in /chosen.
> 
> Example:
> of_fixup_chosen bootloader-version $global.version

This is already done, See commit e96dc23280c43dd6b026ea71bcbaf3353abb4c83

> of_fixup_chosen reset-reason $global.system.reset

See 58243d98b3f8e000c674a78a9466bd2fce213cc6

> of_fixup_chosen serial $serial_number

No generic support for this one though.

Sascha


-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox

Re: Modifying device-tree: /chosen

[Baeuerle, Florian]

Hi Sascha,

Am Donnerstag, den 24.05.2018, 10:20 +0200 schrieb s.hauer@pengutronix.de:
> On Thu, May 24, 2018 at 08:13:44AM +0000, Baeuerle, Florian wrote:
> > Hi Sascha,
> > 
> > so I think we need a command, similar to of_property:
> > 
> > of_fixup_property [-sd] NODE PROPERTY VALUE
> > 
> > or should it rather be a new option for of_property, like this:
> > 
> > of_property [-sdf] NODE [PROPERTY] [VALUES]
> 
> I would first try it as a new option to of_property.
> If for some reason this turns out to be ugly, let me know.

of_property and of_node are pretty similar with regard to their options.

Do you want them to stay the same, so I'd also have to implement this
fixup functionality to of_node?

> 
> Sascha
> 
_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox