Can request_firmware be called from a platform_driver ?

[Dave Hylands]

Hi Mike,

On Wed, Apr 18, 2012 at 11:07 AM, Holmes, Michael A (Mike)
<Mike.Holmes at lsi.com> wrote:
> Hi
>
> I have a fully working system to which I want to add the request firmware
> mechanism to an existing platform driver I have working.
>
> I instrumented mdev in busybox 1.5.1 and in firmware_class.c 2.6.35 so that
> I could figure this out.
>
> What I see with firmware_request() is that the kernel makes the firmware
> request and does not find any firmware and mdev sees nothing.
>
> However if I change my code to do request_firmare_nowait(), the entire
> system comes up and about 30seconds in the timeout calls my kernel side
> continue for request_firmare_nowait() and I DO now see my request handled by
> mdev, however it is a REMOVE request not the ADD request.
>
> All this makes me think that platform drivers exist before the hotplug
> mechanism is able to operate, is this true ?

Well, request_firmware is ultimately serviced by a user-space process.

So platform drivers compiled statically into the kernel get
initialized long before user-space starts.

Platform drivers compiled as modules will get the firmware loaded much
more quickly after loading the module.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com