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

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Message-ID: <20200526152844.GA5809@rowland.harvard.edu>
Date:   Tue, 26 May 2020 11:28:44 -0400
From:   Alan Stern <stern@...land.harvard.edu>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Krzysztof Wilczyński <kw@...ux.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Johan Hovold <johan@...nel.org>,
        Alex Elder <elder@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Felipe Balbi <balbi@...nel.org>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        John Stultz <john.stultz@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        greybus-dev@...ts.linaro.org, netdev <netdev@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        linux-s390@...r.kernel.org,
        "open list:TARGET SUBSYSTEM" <linux-scsi@...r.kernel.org>,
        "open list:ULTRA-WIDEBAND \(UWB\) SUBSYSTEM:" 
        <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 8/8] net/iucv: Use the new device_to_pm() helper to
 access struct dev_pm_ops

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@...ux.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