linux-kernel - Re: [PATCH] PCI: tegra: Use PTR_ERR_OR

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Date:   Wed, 30 Aug 2017 11:26:13 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Himanshu Jha <himanshujha199640@...il.com>, bhelgaas@...gle.com,
        jonathanh@...dia.com, linux-tegra@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: tegra: Use PTR_ERR_OR_ZERO

On Wed, Aug 30, 2017 at 04:25:47PM +0200, Thierry Reding wrote:
> On Wed, Aug 30, 2017 at 08:59:31AM -0500, Bjorn Helgaas wrote:
> > On Tue, Aug 29, 2017 at 03:55:17PM +0200, Thierry Reding wrote:
> > > On Tue, Aug 29, 2017 at 07:09:00PM +0530, Himanshu Jha wrote:
> > > > Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR
> > > > 
> > > > Signed-off-by: Himanshu Jha <himanshujha199640@...il.com>
> > > > ---
> > > >  drivers/pci/host/pci-tegra.c | 5 +----
> > > >  1 file changed, 1 insertion(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> > > > index 9c40da5..90cda5b 100644
> > > > --- a/drivers/pci/host/pci-tegra.c
> > > > +++ b/drivers/pci/host/pci-tegra.c
> > > > @@ -1156,10 +1156,7 @@ static int tegra_pcie_resets_get(struct tegra_pcie *pcie)
> > > >  		return PTR_ERR(pcie->afi_rst);
> > > >  
> > > >  	pcie->pcie_xrst = devm_reset_control_get_exclusive(dev, "pcie_x");
> > > > -	if (IS_ERR(pcie->pcie_xrst))
> > > > -		return PTR_ERR(pcie->pcie_xrst);
> > > > -
> > > > -	return 0;
> > > > +	return PTR_ERR_OR_ZERO(pcie->pcie_xrst);
> > > >  }
> > > 
> > > I'm not a big fan of this construct because it's a pain to undo this if
> > > ever we need to add code to this function. But since we do have scripts
> > > that will flag this, I guess this would pop up every now and again. The
> > > driver is unlikely to change in this part, too, so:
> > 
> > Thanks for pointing this out.  Do you know what the benefit of
> > PTR_ERR_OR_ZERO() is?  To me, it makes the following code harder
> > to read because the error tests are no longer parallel:
> > 
> >   ...
> >   res->ahb_reset = devm_reset_control_get(dev, "ahb");
> >   if (IS_ERR(res->ahb_reset))
> >     return PTR_ERR(res->ahb_reset);
> > 
> >   res->por_reset = devm_reset_control_get(dev, "por");
> >   if (IS_ERR(res->por_reset))
> >     return PTR_ERR(res->por_reset);
> > 
> >   res->phy_reset = devm_reset_control_get(dev, "phy");
> >   return PTR_ERR_OR_ZERO(res->phy_reset);
> > 
> > So I'd be inclined to avoid it unless there's some significant benefit.
> 
> Yeah, I don't like the optics much either. Aside from the fact that it
> reduces the line count, I'm not aware of any benefits that this inline
> function has. It doesn't have any side-effects or anything, just wraps
> the common pattern into a single line.
> 
> Looking at the history of the semantic patch that is the basis for the
> conversions (scripts/coccinelle/api/ptr_ret.cocci), or the static inline
> function itself, no rationale is given for why people prefer this. I've
> certainly seen such patches applied in some cases, but I've also seen
> other maintainers (including myself) reject them because of personal
> preference.

OK, I'm going to drop this then.