Re: [PATCH v6 5/6] PCI/sysfs: Only show value when driver_override is not NULL

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 3 Jun 2021 18:23:34 -0500
Bjorn Helgaas <helgaas@kernel.org> wrote:

> [+cc Alex, FYI]
> 
> On Thu, Jun 03, 2021 at 12:01:11AM +0000, Krzysztof Wilczyński wrote:
> > Only expose the value of the "driver_override" variable through the
> > corresponding sysfs object when a value is actually set.  
> 
> This changes the attribute contents from "(null)" to an empty
> (zero-length) file when no driver override has been set.
> 
> There are a few other driver_override_show() functions.  Most don't
> check the pointer so they'll show "(null)".  One (spi.c) checks and
> shows an empty string ("", file containing a single NULL character)
> instead of an empty (zero-length) file.

Yeah, "(null)" was the expected output in this case.  It looks like
this might break driverctl.  Thanks,

Alex
 
> > Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
> > Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> > ---
> >  drivers/pci/pci-sysfs.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> > index 5d63df7c1820..4e9f582ca10f 100644
> > --- a/drivers/pci/pci-sysfs.c
> > +++ b/drivers/pci/pci-sysfs.c
> > @@ -580,10 +580,11 @@ static ssize_t driver_override_show(struct device *dev,
> >  				    struct device_attribute *attr, char *buf)
> >  {
> >  	struct pci_dev *pdev = to_pci_dev(dev);
> > -	ssize_t len;
> > +	ssize_t len = 0;
> >  
> >  	device_lock(dev);
> > -	len = sysfs_emit(buf, "%s\n", pdev->driver_override);
> > +	if (pdev->driver_override)
> > +		len = sysfs_emit(buf, "%s\n", pdev->driver_override);
> >  	device_unlock(dev);
> >  	return len;
> >  }
> > -- 
> > 2.31.1
> >   
>