On Tue, Jul 30, 2019 at 04:25:56PM +0100, Thomas Preston wrote:
> On 30/07/2019 15:19, Mark Brown wrote:

> > It is unclear what this mutex usefully protects, it only gets taken when
> > writing to the debugfs file to trigger this diagnostic mode but doesn't
> > do anything to control interactions with any other code path in the
> > driver.

> If another process reads the debugfs node "diagnostic" while the turn-on 
> diagnostic mode is running, this mutex prevents the second process
> restarting the diagnostics.

> This is redundant if debugfs reads are atomic, but I don't think they are.

Like I say it's not just debugfs though, there's the standard driver
interface too.