linux-kernel - Re: [RFC] dt/platform: Use cell-index for device naming if available

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Date:	Sun, 11 Nov 2012 17:49:56 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Rob Herring <robherring2@...il.com>
Cc:	Stepan Moskovchenko <stepanm@...eaurora.org>,
	devicetree-discuss@...ts.ozlabs.org,
	David Brown <davidb@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] dt/platform: Use cell-index for device naming if available

On Sun, Nov 11, 2012 at 2:32 AM, Rob Herring <robherring2@...il.com> wrote:
> On 11/09/2012 06:48 PM, Stepan Moskovchenko wrote:
>> Use the cell-index property to construct names for platform
>> devices, falling back on the existing scheme of using the
>> device register address if cell-index is not specified.
>>
>> The cell-index property is a more useful device identifier,
>> especially in systems containing several numbered instances
>> of a particular hardware block, since it more easily
>> illustrates how devices relate to each other.
>>
>> Additionally, userspace software may rely on the classic
>> <name>.<id> naming scheme to access device attributes in
>> sysfs, without having to know the physical addresses of
>> that device on every platform the userspace software may
>> support. Using cell-index for device naming allows the
>> device addresses to be hidden from userspace and to be
>> exposed by logical device number without having to rely on
>> auxdata to perform name overrides. This allows userspace to
>> make assumptions about which sysfs nodes map to which
>> logical instance of a specific hardware block.
>>
>> Signed-off-by: Stepan Moskovchenko <stepanm@...eaurora.org>
>> ---
>> I had also considered using something like the linux,label property to allow
>> custom names for platform devices without resorting to auxdata, but the
>> cell-index approach seems more in line with what cell-index was intended for
>> and with what the pre-DT platform device naming scheme used to be. Please let
>> me know if you think there is a better way to accomplish this.
>>
>> This is just being sent out as an RFC for now. If there are no objections, I
>> will send this out as an official patch, along with (or combined with) a patch
>> to fix up the device names in things like clock tables of any affected
>> platforms.
>
> cell-index is basically deprecated. This has been discussed multiple
> times in the past. You can use auxdata if you really need to have the
> old name.

Actually, I think it would be fine to use an /aliases entry to set the
device name. That's the place to put global namespace information.

g.
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