Re: [PATCH 8/8] net/iucv: Use the new device_to_pm() helper to access struct dev_pm_ops

[Alan Stern <stern@rowland.harvard.edu>]

On Tue, May 26, 2020 at 05:19:07PM +0200, Rafael J. Wysocki wrote:
> On Tue, May 26, 2020 at 5:07 PM Krzysztof Wilczyński <kw@linux.com> wrote:
> >
> > Hello Greg,
> >
> > [...]
> > > It's "interesting" how using your new helper doesn't actually make the
> > > code smaller.  Perhaps it isn't a good helper function?
> >
> > The idea for the helper was inspired by the comment Dan made to Bjorn
> > about Bjorn's change, as per:
> >
> >   https://lore.kernel.org/driverdev-devel/20191016135002.GA24678@kadam/
> >
> > It looked like a good idea to try to reduce the following:
> >
> >   dev->driver && dev->driver->pm && dev->driver->pm->prepare
> >
> > Into something more succinct.  Albeit, given the feedback from yourself
> > and Rafael, I gather that this helper is not really a good addition.
> 
> IMO it could be used for reducing code duplication like you did in the
> PCI code, but not necessarily in the other places where the code in
> question is not exactly duplicated.

The code could be a little more succinct, although it wouldn't fit every 
usage.  For example,

#define pm_do_callback(dev, method) \
	(dev->driver && dev->driver->pm && dev->driver->pm->callback ? \
	dev->driver->pm->callback(dev) : 0)

Then the usage is something like:

	ret = pm_do_callback(dev, prepare);

Would this be an overall improvement?

Alan Stern