linux-kernel - Re: [PATCH] ARM: /proc/cpuinfo: Use DT machine name when possible

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Date:	Wed, 3 Dec 2014 18:33:08 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	Will Deacon <will.deacon@....com>,
	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
	Sebastian Reichel <sre@...ian.org>,
	Pavel Machek <pavel@....cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: /proc/cpuinfo: Use DT machine name when possible

On Mon, Nov 24, 2014 at 4:19 PM, Pali Rohár <pali.rohar@...il.com> wrote:
> On Wednesday 18 June 2014 22:46:19 Rob Herring wrote:
>> On Wed, Jun 18, 2014 at 2:22 PM, Pali Rohár
> <pali.rohar@...il.com> wrote:
>> > On Wednesday 18 June 2014 21:07:35 Rob Herring wrote:
>> >> On Wed, Jun 18, 2014 at 11:54 AM, Pali Rohár
>> >
>> > <pali.rohar@...il.com> wrote:
>> >> > Machine name from board description is some generic name
>> >> > on DT kernel. DT provides machine name property which is
>> >> > specific for board, so use it instead generic one when
>> >> > possible.
>> >> >

[...]

>> > Basically in DT kernel is missing Hardware, Revision and
>> > probably also Serial key. (Now I used only qemu for testing
>> > which set serial key to 0). All these informations is used
>> > by userspace applications which determinate how to behave.
>>
>> It is somewhat fragile to expect the name in the DT to match
>> the old name from the kernel. As your patch to n900 dts
>> shows, we'd probably have to update every dts file to make
>> them match. While I think we should work to remove this
>> string from the kernel, userspace depending on the DT model
>> string is a bad idea. For example, if you had some platform
>> with multiple OEMs just rebranding the same base design, they
>> may all want to put their own model string into each product.
>> The true h/w id is the compatible string.
>>
>> Serial number is easy. There is already a standard although
>> not widely used property for it with "/serial-number". You
>> just need to wire it up to cpuinfo.
>>
>
> There is no "/serial-number" property in kernel:
>
> $ ls -l -a /sys/bus/soc/devices/soc0/
> drwxr-xr-x    3 0        0                0 Jan  1 00:00 .
> drwxr-xr-x   18 0        0                0 Jan  1 00:00 ..
> -r--r--r--    1 0        0             4096 Jan  1 00:00 family
> -r--r--r--    1 0        0             4096 Jan  1 00:00 machine
> drwxr-xr-x    2 0        0                0 Jan  1 00:00 power
> -r--r--r--    1 0        0             4096 Jan  1 00:00 revision
> lrwxrwxrwx    1 0        0                0 Jan  1 00:00
> subsystem -> ../../bus/soc
> -r--r--r--    1 0        0             4096 Jan  1 00:00 type
> -rw-r--r--    1 0        0             4096 Jan  1 00:00 uevent

Wrong place. If you put /serial-number in your DT, then it will be in
/proc/device-tree/serial-number.

If you want to wire that up to /proc/cpuinfo, I would be fine with that.

Rob
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