linux-kernel - Re: [PATCH] PCI: merge slot and bus reset implementations

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Message-ID: <20210406081626.31f19c0f@x1.home.shazbot.org>
Date:   Tue, 6 Apr 2021 08:16:26 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     Raphael Norwitz <raphael.norwitz@...anix.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "ameynarkhede03@...il.com" <ameynarkhede03@...il.com>
Subject: Re: [PATCH] PCI: merge slot and bus reset implementations

On Sun, 4 Apr 2021 11:04:32 +0300
Leon Romanovsky <leon@...nel.org> wrote:

> On Thu, Apr 01, 2021 at 10:56:16AM -0600, Alex Williamson wrote:
> > On Thu, 1 Apr 2021 15:27:37 +0300
> > Leon Romanovsky <leon@...nel.org> wrote:
> >   
> > > On Thu, Apr 01, 2021 at 05:37:16AM +0000, Raphael Norwitz wrote:  
> > > > Slot resets are bus resets with additional logic to prevent a device
> > > > from being removed during the reset. Currently slot and bus resets have
> > > > separate implementations in pci.c, complicating higher level logic. As
> > > > discussed on the mailing list, they should be combined into a generic
> > > > function which performs an SBR. This change adds a function,
> > > > pci_reset_bus_function(), which first attempts a slot reset and then
> > > > attempts a bus reset if -ENOTTY is returned, such that there is now a
> > > > single device agnostic function to perform an SBR.
> > > > 
> > > > This new function is also needed to add SBR reset quirks and therefore
> > > > is exposed in pci.h.
> > > > 
> > > > Link: https://lkml.org/lkml/2021/3/23/911
> > > > 
> > > > Suggested-by: Alex Williamson <alex.williamson@...hat.com>
> > > > Signed-off-by: Amey Narkhede <ameynarkhede03@...il.com>
> > > > Signed-off-by: Raphael Norwitz <raphael.norwitz@...anix.com>
> > > > ---
> > > >  drivers/pci/pci.c   | 17 +++++++++--------
> > > >  include/linux/pci.h |  1 +
> > > >  2 files changed, 10 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > > > index 16a17215f633..12a91af2ade4 100644
> > > > --- a/drivers/pci/pci.c
> > > > +++ b/drivers/pci/pci.c
> > > > @@ -4982,6 +4982,13 @@ static int pci_dev_reset_slot_function(struct pci_dev *dev, int probe)
> > > >  	return pci_reset_hotplug_slot(dev->slot->hotplug, probe);
> > > >  }
> > > >  
> > > > +int pci_reset_bus_function(struct pci_dev *dev, int probe)
> > > > +{
> > > > +	int rc = pci_dev_reset_slot_function(dev, probe);
> > > > +
> > > > +	return (rc == -ENOTTY) ? pci_parent_bus_reset(dev, probe) : rc;    
> > > 
> > > The previous coding style is preferable one in the Linux kernel.
> > > int rc = pci_dev_reset_slot_function(dev, probe);
> > > if (rc != -ENOTTY)
> > >   return rc;
> > > return pci_parent_bus_reset(dev, probe);  
> > 
> > 
> > That'd be news to me, do you have a reference?  I've never seen
> > complaints for ternaries previously.  Thanks,  
> 
> The complaint is not to ternaries, but to the function call as one of
> the parameters, that makes it harder to read.

Sorry, I don't find a function call as a parameter to a ternary to be
extraordinary, nor do I find it to be a discouraged usage model within
the kernel.  This seems like a pretty low bar for hard to read code.