Date:   Tue, 28 Sep 2021 21:29:36 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Uwe Kleine-König <uwe@...ine-koenig.org>,
        Oliver O'Halloran <oohall@...il.com>,
        Russell Currey <ruscur@...sell.cc>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        linux-pci@...r.kernel.org, Alexander Duyck <alexanderduyck@...com>,
        oss-drivers@...igine.com, Paul Mackerras <paulus@...ba.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Michael Ellerman <mpe@...erman.id.au>,
        Rafał Miłecki <zajec5@...il.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Ido Schimmel <idosch@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Yisen Zhuang <yisen.zhuang@...wei.com>,
        Vadym Kochan <vkochan@...vell.com>, Michael Buesch <m@...s.ch>,
        Jiri Pirko <jiri@...dia.com>,
        Salil Mehta <salil.mehta@...wei.com>, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        Taras Chornyi <tchornyi@...vell.com>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        linux-crypto@...r.kernel.org, kernel@...gutronix.de,
        Simon Horman <simon.horman@...igine.com>,
        linuxppc-dev@...ts.ozlabs.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v4 4/8] PCI: replace pci_dev::driver usage that gets the
 driver name

Hello,

On Tue, Sep 28, 2021 at 12:17:59PM -0500, Bjorn Helgaas wrote:
> [+to Oliver, Russell for eeh_driver_name() question below]
> 
> On Mon, Sep 27, 2021 at 10:43:22PM +0200, Uwe Kleine-König wrote:
> > From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > 
> > struct pci_dev::driver holds (apart from a constant offset) the same
> > data as struct pci_dev::dev->driver. With the goal to remove struct
> > pci_dev::driver to get rid of data duplication replace getting the
> > driver name by dev_driver_string() which implicitly makes use of struct
> > pci_dev::dev->driver.
> 
> When you repost to fix the build issue, can you capitalize the subject
> line to match the other?

Yes, sure.

> Also, would you mind using "pci_dev.driver" instead of
> "pci_dev::driver"?  AFAIK, the "::" operator is not actually part of
> C, so I think it's more confusing than useful.

pci_dev.driver doesn't work either in C because pci_dev is a type and
not a variable. This is probably subjective, but for me pci_dev.driver
looks definitively stranger than pci_dev::driver. And :: is at least not
unseen in the kernel commit logs. (git log --grep=::)
But if you insist I can change to .

> > diff --git a/arch/powerpc/include/asm/ppc-pci.h b/arch/powerpc/include/asm/ppc-pci.h
> > index 2b9edbf6e929..e8f1795a2acf 100644
> > --- a/arch/powerpc/include/asm/ppc-pci.h
> > +++ b/arch/powerpc/include/asm/ppc-pci.h
> > @@ -57,7 +57,14 @@ void eeh_sysfs_remove_device(struct pci_dev *pdev);
> >  
> >  static inline const char *eeh_driver_name(struct pci_dev *pdev)
> >  {
> > -	return (pdev && pdev->driver) ? pdev->driver->name : "<null>";
> > +	if (pdev) {
> > +		const char *drvstr = dev_driver_string(&pdev->dev);
> > +
> > +		if (strcmp(drvstr, ""))
> > +			return drvstr;
> > +	}
> > +
> > +	return "<null>";
> 
> Can we just do this?
> 
>   if (pdev)
>     return dev_driver_string(&pdev->dev);
> 
>   return "<null>";

Works for me, too. It behaves a bit differerently than my suggestion
(which nearly behaves identical to the status quo), but only in some
degenerated cases.

> I think it's more complicated than it's worth to include a strcmp().
> It's possible this will change those error messages about "Might be
> infinite loop in %s driver", but that doesn't seem like a huge deal.
> 
> I moved Oliver to "to:" and added Russell in case they object.
> 
> >  }
> >  
> >  #endif /* CONFIG_EEH */
> > diff --git a/drivers/bcma/host_pci.c b/drivers/bcma/host_pci.c
> > index 69c10a7b7c61..0973022d4b13 100644
> > --- a/drivers/bcma/host_pci.c
> > +++ b/drivers/bcma/host_pci.c
> > @@ -175,9 +175,10 @@ static int bcma_host_pci_probe(struct pci_dev *dev,
> >  	if (err)
> >  		goto err_kfree_bus;
> >  
> > -	name = dev_name(&dev->dev);
> > -	if (dev->driver && dev->driver->name)
> > -		name = dev->driver->name;
> > +	name = dev_driver_string(&dev->dev);
> > +	if (!strcmp(name, ""))
> > +		name = dev_name(&dev->dev);
> >  	err = pci_request_regions(dev, name);
> 
> Again seems more complicated than it's worth to me.  This is in the
> driver's .probe() method, so really_probe() has already set
> "dev->driver = drv", which means dev->driver is always set to
> &bcma_pci_bridge_driver here, and bcma_pci_bridge_driver.name is
> always "bcma-pci-bridge".
> 
> Almost all callers of pci_request_regions() just hardcode the driver
> name or use a DRV_NAME #define
> 
> So I think we should just do:
> 
>   err = pci_request_regions(dev, "bcma-pci-bridge");

Yes, looks right. I'd put this in a separate patch.

> >  	if (err)
> >  		goto err_pci_disable;
> > [...]
> > diff --git a/drivers/ssb/pcihost_wrapper.c b/drivers/ssb/pcihost_wrapper.c
> > index 410215c16920..4938ed5cfae5 100644
> > --- a/drivers/ssb/pcihost_wrapper.c
> > +++ b/drivers/ssb/pcihost_wrapper.c
> > @@ -78,9 +78,11 @@ static int ssb_pcihost_probe(struct pci_dev *dev,
> >  	err = pci_enable_device(dev);
> >  	if (err)
> >  		goto err_kfree_ssb;
> > -	name = dev_name(&dev->dev);
> > -	if (dev->driver && dev->driver->name)
> > -		name = dev->driver->name;
> > +
> > +	name = dev_driver_string(&dev->dev);
> > +	if (*name == '\0')
> > +		name = dev_name(&dev->dev);
> > +
> >  	err = pci_request_regions(dev, name);
> 
> Also seems like more trouble than it's worth.  This one is a little
> strange but is always called for either b43_pci_bridge_driver or
> b44_pci_driver, both of which have .name set, so I think we should
> simply do:
> 
>   err = pci_request_regions(dev, dev_driver_string(&dev->dev));

yes, agreed, too.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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