Re: [RFD][PATCH] pcielw An alternate pcie hotplug driver

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Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> writes:

> On Thu, 10 Sep 2009 10:31:57 -0600
> Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:
>
>> On Monday 07 September 2009 04:40:22 am Eric W. Biederman wrote:
>> > 
>> > What follows below is my alternate pcie hotplug driver.
>> > It is very stupid, very simple and very robust.
>> > 
>> > This driver should work on any pcie hotplug bridge that
>> > only has support for the interrupt when the pcie link
>> > comes or down, and that sets the hotplug and the hotplug
>> > surprise bits.
>> > 
>> > I wrote this because in my environment the pciehp driver
>> > totally fails and 500 lines of code are much easier to
>> > debug than 3000.
>> > 
>> > Now that I have the code working I'm looking for the best
>> > path to get a driver I can use into the mainstream kernel.
>> 
>> I think it'd be great to simplify pciehp, and pcielw looks
>> nice and clean.
>> 
>> I think pciehp/acpiphp/pcielw are somewhat user-unfriendly
>> because (a) it's hard for a user to figure out which to use,
>> and (b) there's no nice way to autoload them because there's
>> nothing that connects them to a udev event.
>> 
>> My personal opinion is that we shouldn't merge pcielw alongside
>> pciehp because it would make the user confusion worse and dilute
>> the already small testing pool.
>> 
>> We could address the autoload issue by making pciehp/pcielw part
>> of the pcieport driver.  That would simplify the code as well as
>> the user experience, but maybe there's some reason to keep them
>> separate.
>> 
>> I think it'd be nice to have a series of evolutionary patches
>> to transform pciehp rather than replacing it wholesale.  Otherwise,
>> bisection (one of the few tools we non-expert masses have) won't
>> be as useful.
>
> Agreed.  Is that something you'd be interested in doing, Eric?

Time permitting, I will take a stab at it.  It looks like things are
pretty healthy on the development front so it should be doable.

There is a fair amount of heavy lifting.  Would it help if I tossed
up a git tree where I accumulate the changes as I make them.  Then
you can just pull them as you have time?

> We have a fairly active hotplug community (most of the patches in
> any given release seem to be hotplug related) so you shouldn't have
> a shortage of testers...

Eric
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