linux-kernel - Re: [PATCH] RFC: MFD: driver for Atmel Microcontroller on iPaq h3xxx

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Date:	Wed, 2 Apr 2014 13:14:40 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King <linux@....linux.org.uk>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Alessandro Gardich <gremlin@...mlin.it>,
	Dmitry Artamonow <mad_soft@...ox.ru>
Subject: Re: [PATCH] RFC: MFD: driver for Atmel Microcontroller on iPaq h3xxx

> > Does it matter that you're using:
> >
> >   module_platform_driver();
> >
> > ... yet you can't build this as a module?
> 
> I think it's a conceptual thing. Module means two things (IIUC):
> (a) it is a run-time loadable module
> (b) it's a piece of compartmentalized code
> 
> In this case the macro refers to (b). module_platform_driver()
> resolves to module_driver() from <linux/device.h>
> and it's clearly a core part of the device core and available
> no matter whether the file is used as module at runtime or not.
> It just simplifies the initcalls and that's no different depending
> on whether the code is compiled-in or used as module.

Fair enough.

> >> +     case MSG_KEYBOARD:
> >> +             if (micro->key != NULL)
> >
> > !micro->key
> 
> I guess you mean if (micro->key) {} rather than the !invert,
> but I get it, changed everywhere we check for != NULL like this.

Yes sorry, I'm so used to seeing (thing == NULL), but you knew what I
meant.

[...]

> >> +static int micro_suspend(struct device *dev)
> >> +{
> >> +     return 0;
> >> +}
> >
> > Doesn't the PM framework check for NULL .suspend?
> 
> No it's just like:
> 
> #ifdef CONFIG_SUSPEND
>         case PM_EVENT_SUSPEND:
>                 return ops->suspend;
>         case PM_EVENT_RESUME:
>                 return ops->resume;
> #endif /* CONFIG_SUSPEND */
> 
> (drivers/power/main.c)

  base/ ---^

Right, but a NULL return _is_ valid from here and is subsequently dealt
with in the correct way.

[...]
        callback = pm_op(dev->type->pm, state);
        goto Driver;

[...]

Driver:
       if (!callback && dev->driver && dev->driver->pm) {
               info = "driver ";
               callback = pm_op(dev->driver->pm, state);
       }
[...]

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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