Re: u-boot DT configuration node

From: Michal Simek <michal.simek@xilinx.com>
To: Mark Kettenis <mark.kettenis@xs4all.nl>,
	Michal Simek <michal.simek@xilinx.com>
Cc: robh@kernel.org, devicetree@vger.kernel.org,
	u-boot@lists.denx.de, trini@konsulko.com,
	loic.poulain@linaro.org
Subject: Re: u-boot DT configuration node
Date: Thu, 2 Apr 2020 08:05:36 +0200	[thread overview]
Message-ID: <ff4d0123-ca41-630e-322f-5251ee1e308e@xilinx.com> (raw)
In-Reply-To: <016159802e74c8a2@bloch.sibelius.xs4all.nl>

On 01. 04. 20 20:09, Mark Kettenis wrote:
>> From: Michal Simek <michal.simek@xilinx.com>
>> Date: Wed, 1 Apr 2020 11:23:13 +0200
>>
>> Hi Rob and others,
>>
>> for couple of years already u-boot is using config node in root DT for
>> u-boot configuration.
>>
>> Here is one example in u-boot source code.
>> https://gitlab.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/exynos5250-spring.dts#L47
>>
>> And here is dt binding description
>> https://gitlab.denx.de/u-boot/u-boot/-/blob/master/doc/device-tree-bindings/config.txt
>>
>> I was checking dt binding specification and there no such a thing
>> described there. It means I expect this is more adhoc u-boot solution.
>> We have reached the point where could be beneficial to put some u-boot
>> specific configurations to DT.
>>
>> Actually I have done similar thing some time ago too by using chosen
>> node and add xilinx specific property there to point to eeprom.
>> https://gitlab.denx.de/u-boot/u-boot/-/blob/master/arch/arm/dts/zynqmp-zcu102-revA.dts#L39
>>
>> I think it is a time to discuss it and do it properly.
>>
>> First of all my question is where we could list SW prefixes to make sure
>> that they are listed and everybody is aware about it. We have
>> vendor-prefixes and we should have a way to record also prefixes for sw
>> projects. U-Boot is using u-boot. Xen has file in the kernel with using
>> xen prefix. At least these two should be listed.
> 
> OpenBSD is using "openbsd," as a prefix.  I've always thought it would
> be good to have it listed in the list of vendor prefixes there.  In an
> open source world it shouldn't matter whether an entity sells
> something or not.  And in fact "inux," is already there.  And so is
> "qemu,".

Good we have more.

> 
>> Next my question is what is the recommended way to pass sw specific
>> parameters via DT? I think using chosen node is more appropriate then
>> adhoc config node. Or is there a better way how this should be done?
> 
> On OpenBSD we do indeed use the the chosen node to pass information
> between the bootloader and the kernel.

Can you please point me to any example or description what you are
adding there?

Thanks,
Michal