linux-kernel - Re: [PATCH v2] net: rfkill: add generic gpio rfkill driver

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Date:	Thu, 12 May 2011 11:52:57 -0700
From:	Rhyland Klein <rklein@...dia.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	"olof@...om.net" <olof@...om.net>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] net: rfkill: add generic gpio rfkill driver

On Thu, 2011-05-12 at 11:40 -0700, Johannes Berg wrote:
> On Thu, 2011-05-12 at 11:23 -0700, Rhyland Klein wrote:
> 
> > > Are you sure starting out with UNSPECIFIED works? Then you'll always
> > > change, but if the clock was enabled already you still enable it on the
> > > first set_block() from rfkill, which still has the refcount problem, no?
> > > It seems to me that the original state has to be passed in from the
> > > platform?
> 
> > I thought about that. But I decided the clock that it is possible to
> > have the clock used for the radio used for something else right? 
> 
> Sure.
> 
> > in
> > which case, the driver will leave the clk in whatever state it initially
> > finds it. I.e. if the clock is disabled, then it will enable it only
> > once and work, if it is enabled, it will add a refcount (only once) and
> > then work and disable it again only once. It never changes the refcount
> > in either direction by more than 1, and this way the initial setting of
> > the clock is irrelevant. The board files can simply initialize the block
> > as off if that is the initial clk state they want.
> 
> The issue is that depending on how you boot, the first refcount change
> might be +1 or it might be -1.
> 
> If rfkill decides that at the time of loading wifi should be off, then
> the first change would be -1, and after that it would flip between 0 and
> -1.
> 
> If, on the other hand, rfkill decides that at the time of loading the
> driver wifi should be on, then the first change would be +1 and it'll
> flip between 0 and +1.
> 
> This seems like it'll cause issues at some point, so I think you should
> either allow the driver to set the initial state or hardcode one of
> these possibilities (so at least it's predictable)
> 
> johannes
> 

I won't go negative, if you look, it only will disable clock if it knows
it has already enabled it. 

rhyland

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