linux-kernel - Re: [PATCH v2 02/24] PCI: Set error response in config access defines when ops->read() fails

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Date:   Wed, 20 Oct 2021 20:43:09 +0530
From:   Naveen Naidu <naveennaidu479@...il.com>
To:     Pali Rohár <pali@...nel.org>
Cc:     bhelgaas@...gle.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v2 02/24] PCI: Set error response in config access
 defines when ops->read() fails

On 20/10, Pali Rohár wrote:
> On Friday 15 October 2021 19:58:17 Naveen Naidu wrote:
> > Make PCI_OP_READ and PCI_USER_READ_CONFIG set the data value with error
> > response (~0), when the PCI device read by a host controller fails.
> > 
> > This ensures that the controller drivers no longer need to fabricate
> > (~0) value when they detect error. It also  gurantees that the error
> > response (~0) is always set when the controller drivers fails to read a
> > config register from a device.
> > 
> > This makes error response fabrication consistent and helps in removal of
> > a lot of repeated code.
> > 
> > Suggested-by: Rob Herring <robh@...nel.org>
> > Signed-off-by: Naveen Naidu <naveennaidu479@...il.com>
> > ---
> >  drivers/pci/access.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> > index 46935695cfb9..b3b2006ed1d2 100644
> > --- a/drivers/pci/access.c
> > +++ b/drivers/pci/access.c
> > @@ -42,7 +42,10 @@ int noinline pci_bus_read_config_##size \
> >  	if (PCI_##size##_BAD) return PCIBIOS_BAD_REGISTER_NUMBER;	\
> >  	pci_lock_config(flags);						\
> >  	res = bus->ops->read(bus, devfn, pos, len, &data);		\
> > -	*value = (type)data;						\
> > +	if (res)									\
> > +		SET_PCI_ERROR_RESPONSE(value);			\
> > +	else										\
> > +		*value = (type)data;						\
> 
> Hello! Just one small comment. It looks like that in this patch is
> broken alignment of backslashes on the end of lines. Prior this patch
> backslashes on all lines were at the same column. With this patch they
> are not.
>

Thank you for spotting this. I apologise for this. I did not configure
my editor properlly so I couldn't recognize this error. But I'll fix
this when I send the v3

> >  	pci_unlock_config(flags);					\
> >  	return res;							\
> >  }
> > @@ -228,7 +231,10 @@ int pci_user_read_config_##size						\
> >  	ret = dev->bus->ops->read(dev->bus, dev->devfn,			\
> >  					pos, sizeof(type), &data);	\
> >  	raw_spin_unlock_irq(&pci_lock);				\
> > -	*val = (type)data;						\
> > +	if (ret)								\
> > +		SET_PCI_ERROR_RESPONSE(val);			\
> > +	else									\
> > +		*val = (type)data;						\
> >  	return pcibios_err_to_errno(ret);				\
> >  }									\
> >  EXPORT_SYMBOL_GPL(pci_user_read_config_##size);
> > -- 
> > 2.25.1
> >