Re: [RFC PATCH 1/2] driver core: introduce module_platform_driver_match_and_probe

[Rob Herring]

On Thu, Nov 21, 2013 at 6:47 AM, Grant Likely <grant.likely@xxxxxxxxxx> wrote:
> On Wed, 30 Oct 2013 01:12:50 -0500, Rob Herring <robherring2@xxxxxxxxx> wrote:
>> From: Rob Herring <rob.herring@xxxxxxxxxxx>
>>
>> Introduce a helper to match, create and probe a platform device. This
>> is for drivers such as cpuidle or cpufreq that typically don't have a
>> bus device node and need to match on a system-level compatible property.
>>
>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> Cc: Grant Likely <grant.likely@xxxxxxxxxx>
>> Signed-off-by: Rob Herring <rob.herring@xxxxxxxxxxx>
>
> Oh, ick. Please no. If a platform_device isn't getting created for a
> device tree node, then we should be asking why it isn't getting created
> and fix the core logic rather than trying to bodge it in the driver init
> code.
>
> We should never be creating and registering devices in module init code.
> We've spent the last 4 years trying to get away from that.

This is for devices that have no DT device node to be associated with
and therefore will never have a device created by the core DT code.
Instead the devices are created based off of the root compatible
property. cpuidle drivers are one such example [1]. We already do this
today by putting the platform device creation in the
machine_desc.init_machine function which is a conditional initcall.
The motivation for changing this is how to support drivers like this
on arm64 which doesn't want any platform code or machine_desc. At
least historically, we didn't want DT nodes of Linux specific devices
in the DT. So, how would you propose to solve this problem?

Rob

[1] https://git.kernel.org/cgit/linux/kernel/git/robh/linux.git/commit/?h=highbank-rm-mach-desc&id=f4c00839748688c480c56952cfc06d49aebe1162
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