Re: [PATCH 2/5] drivercore: Add driver probe deferral mechanism

Grant Likely
2011-10-14T19:07:21Z

On Fri, Oct 14, 2011 at 12:39 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Fri, 14 Oct 2011, Grant Likely wrote:
>> I'd be much happier to find a way to do this in core code though.  And
>> there is still a potential race condition here.  For example, if G is
>> in the middle of it's probe routine, and D gets probed between G
>> registering GPIOs and calling dpm_move_last(), then we're in the same
>> boat again.
>
> Of course, this means that G must call dpm_move_last() _before_
> registering its GPIOs.  So the overall flow of a probe routine is
> simple enough:
>
>        1. Check that all the resources you need are available.
>
>        2. If not, defer your probe.  If yes, call dpm_move_last().
>
>        3. Finish the probe, including registration of resources
>           that will be available to other drivers (such as child
>           devices).

Alright, let's start with this. That also means that the current
probe deferral patch doesn't need to have any knowledge of dpm_list
added to it. It will be required only of the users.

I'd still like to look closely at the ordering of dpm_list for the
non-deferred use case, but that can be an entirely separate patch set.
It doesn't need to block the probe deferral work.

g.