linux-kernel - Re: sl811h_suspend() and PM_EVENT

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Date:	Tue, 6 Aug 2013 17:21:36 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Shuah Khan <shuah.kh@...sung.com>
cc:	"rjw@...k.pl" <rjw@...k.pl>, "pavel@....cz" <pavel@....cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: sl811h_suspend() and PM_EVENT_PRETHAW state handling

On Tue, 6 Aug 2013, Shuah Khan wrote:

> With the dev_pm_ops model, drivers have to provide interfaces for each 
> one of these states.

No, they don't.  They can leave out interfaces if they want.

>  In this case, there will be a conflict since 
> pm_op() treats this state as freeze where as the driver wants to do 
> treat it as a suspend/hibernate. In the case of legacy pm_ops, state is 
> passed in as a parameter and driver could take special action if need 
> be, based on the state, however in dev_pm_ops model, state is not passed 
> in. Instead it is handled with state specific pm_ops interfaces.
> 
> For example, if this driver were to be converted to dev_pm_ops, it would 
> require a freeze interface which will call sl811h_bus_suspend(). Once 
> that is done, PM_EVENT_PRETHAW will be mapped to freeze() ops and 
> sl811h_bus_suspend() will be called instead of port_power(sl811, 0);
> 
> What I am getting at is, there is no provision to handle the special 
> case for PM_EVENT_PRETHAW like in the case of this driver when using 
> dev_pm_ops.

Okay.  So what?

Alan Stern

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