Re: [PATCH] dt: platform: Extract device name from device tree blob

[Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>]

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On Mon, 12 Nov 2012 23:54:40 +0100, Per Förlin <per.forlin-0IS4wlFg1OjSUeElwK9/Pw@public.gmane.org> wrote:
> On 11/12/2012 04:20 PM, Grant Likely wrote:
> > On Mon, Nov 12, 2012 at 2:59 PM, Per Forlin <per.forlin-0IS4wlFg1OjSUeElwK9/Pw@public.gmane.org> wrote:
> >> Add support to extract device name from device tree blob.
> >> If the property "dev-name" is set in the DTS this name will
> >> be used when creating the device.
> >> The auxdata_lookup has precedence and will override
> >> the "dev-name" property.
> > 
> > Using a 'dev-name' property has the same problem that the 'cell-index'
> > properties have in that it is encoding part of the global namespace
> > local to the node and it becomes easy to create collisions. Instead of
> > this check to see if one of the properties in /aliases points to the
> > node and use that for the name.
> > 
> > g.
> > 
> Thanks Grant for your feedback,
> 
> Extract from exynos5250.dtsi:
> -----------
> 	aliases {
> 		spi0 = &spi_0;
> 		spi1 = &spi_1;
> 		spi2 = &spi_2;
> 	};
> 
> 	spi_0: spi@12d20000 {
> ...
> 	};
> 
> 	spi_1: spi@12d30000 {
> ...
> 	};
> 
> 	spi_2: spi@12d40000 {
> ...
> 	};
> ---------------
> 
> Alias refers to the device node. The device node is not aware of the alias.
> 
> How to get a device name from the aliases.
> 1. Traverse all aliases for each device node (time consuming if there are many aliases)
> 2. Make a new function of_alias_get_name(), today there is only of_alias_get_id()
> 3. The functionality of setting device_name based on alias name needs to be optional because one may want to use aliases without changing the name of the device.
> All this is feasible but perhaps not optimal.
> 
> I don't really see how come name space is a big issue in this case. The name space of "dev-name" is local to the device node. A child device node can use the same dev-name as the parent (unless I'm mistaken which happens quite often). Introducing yet another property name pollutes the name space of the device node. Still I think the pros are stronger than the cons.
> 
> Do you still prefer to use the name of the Alias? Could you please elaborate a bit more how this can be done in practice?
> I would agree with you if there was a reference from the device node to the alias.

Oh, I see what you're trying to do. As Lee pointed out you're trying to
make the Linux internal way of matching up clocks and regulators happy.
That is very much a Linux-kernel internal thing and should be solved in
the kernel. Trying to solve it with fixed names in the device tree will
cause problems down the road.

I though you were wanting to have logical names for the devices that
make sense to the user which is how aliases is used now.

So, no, don't do this.

g.


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