Re: [RFC/PATCH] of: platform: Remove unique device name enforcement

On Tue, 20 May 2014 13:30:02 -0500, Rob Herring [off-list ref] wrote:

On Tue, May 20, 2014 at 1:50 AM, Grant Likely [off-list ref] wrote:

quoted

On Sun, 18 May 2014 18:11:07 -0500, Rob Herring [off-list ref] wrote:

quoted

On Sun, May 18, 2014 at 12:01 PM, Ezequiel Garcia
[off-list ref] wrote:

quoted

When creating a device object for a devicetree node, the device name
is created by using the node name and the 'reg' property, to make a name
such as "a000.foo_device".

For certain devices without an associated address, and hence no 'reg' property,
the current code attempts to make a unique name, by using a global integer.
Names look like "foo_device.1", "bar_device.2", and so on.
Examples of such devices are: gpio-keys', backlights and rotary-encoders.

The system cannot know such devices name before hand, given they are determined
by the kernel probe order and by the nodes present in the devicetree. This can
be problematic, on systems that are tied to the device's name, e.g. when
catching hotplug events.

The device's uevent file in sysfs contains both the ->name and
->full_name values for a node. Does that help you?

The big problem is not the structure under /sys/devices, but rather the
symlinks to devices that appear under /sys/bus/*/devices. If two leaf
nodes have the same name, then they will conflict when they get added to
a bus_type's array of devices.

Another way to handle it is to only add the suffix when a conflict
actually occurs. That requires checking first whether or not a name will
conflict and ammending it only when that happens. I don't know if that
can be done nicely. I'll take a look.

That was my idea as well and to move to a local number so you have
something like deviceA, deviceA.1, deviceB, deviceB.1 (maybe the
number is always appended). Perhaps a random number instead so no one
expects the names to be an ABI. ;)

Another idea: how about fix the name to alwasy be the final component of
the path name, followed by phandle. Anything that doesn't have a phandle
can be assigned one at boot. That would guarantee uniqueness without the
cost of trying to find duplicates.

for example:
	uart@10043000:0012

g.

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