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From: Kay Sievers <kay@vrfy.org>
Date: Thu, 22 Nov 2012 20:17:32 +0100
Message-ID: <CAPXgP12fOANaeVQ=8ZMd1q-SdJo0xjsGoVTqs27oe44wXuSCdQ@mail.gmail.com>
Subject: Re: [RFC] driver-core: Remove dummy 'platform_bus'
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Grant Likely <grant.likely@secretlab.ca>, linux-kernel@vger.kernel.org
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On Wed, Nov 21, 2012 at 3:52 PM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> On Wed, Nov 21, 2012 at 02:44:31PM +0000, Grant Likely wrote:
>> The "platform_bus" (note: not platform_bus_type) only exists as an empty
>> directory to put platform devices into. However, it really doesn't make
>> sense to segregate all the platform devices into a sub directory when
>> typically they are memory mapped devices that doen't go through any
>> particular bus. Particularly on embedded type platforms the platform_bus
>> directory doesn't add anything.
>>
>> However, this will probably just end up breaking some userspace that
>> depends on the /sys/devices/platform/ path to be present (no matter how
>> much we protest that userspace must not depend on paths in sysfs). So
>> while I'm seriously proposing this change, it may just be unacceptable
>> ABI breakage
>
> If the devices don't show up under platform/ where are they going to be
> at now, virtual/ ?  That doesn't sound like a good plan, they should be
> somewhere "useful".

Just a note to keep in mind: We usually need and want devices to have
a bus or class. Devices without a "subsystem" are invisible to udev,
and do not get proper coldplug support at bootup.

Kay
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