Re: [PATCH 2/2] pci: Add ignore indicator quirk for devices

[Keith Busch <keith.busch@intel.com>]

On Tue, Aug 23, 2016 at 02:52:21PM -0500, Bjorn Helgaas wrote:
> Everybody probably knows this, but the problem is not with LED control
> per se.  The problem is multiple writers to the Slot Control register.
> Each write to Slot Control is a "command", and software is responsible
> for waiting for one command to complete before writing another (see
> PCIe r3.0, sec 6.7.3.2).
> 
> It's no problem to make pciehp keep its mitts off the LEDs; the
> problem is if ledmon writes Slot Control for the indicators, and
> pciehp writes Slot Control for some other reason at about the same
> time.
> 
> Sinan has a very interesting idea...  Maybe we can work with that.
> Hmm, it looks like if we have an attention indicator, we already put
> an "attention" file in sysfs (see attention_write_file()).  That
> should eventually call into pciehp_set_attention_status(), where we
> currently only support off/on/blink states.
> 
> What if you made a quirk that replaced pciehp_set_attention_status()
> with a special version that supported the extra states you need and
> made ledmon use that sysfs file instead of writing Slot Control
> directly?  Would everything just work?

I'm on board with this idea. I'll get some testing started and send a
new version if/when successful.