linux-kernel - Re: [PATCH v2] PCI/MSI: Simplify the return value of arch_setup_msi

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Message-ID: <20160816210149.GA14976@localhost>
Date:	Tue, 16 Aug 2016 16:01:49 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI/MSI: Simplify the return value of
 arch_setup_msi_irqs

On Wed, Jun 22, 2016 at 11:20:20AM +0800, Shawn Lin wrote:
> No any callers do care whether arch_setup_msi_irqs returns
> -ENOSPC or other error numbers. That means they treat the
> negative numbers in the same way. So there shouldn't make any
> difference to directly return -ENOSPC if finding it's non-zero.

This return value gets returned all the way up to the external
interfaces used by drivers, e.g., pci_enable_msi_range(), so it would
take quite a lot of analysis to assert that *no* caller cares whether
it's -ENOSPC or something else.  I suspect you're right that it
probably doesn't matter, but it looks pretty hard to prove it.

> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
> 
> ---
> 
> Changes in v2:
> - fix warning generated by -Wmisleading-indentation reported by Kbuild robot
> 
>  drivers/pci/msi.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index a080f44..5057219 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -108,7 +108,7 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
>  {
>  	struct msi_controller *chip = dev->bus->msi;
>  	struct msi_desc *entry;
> -	int ret;
> +	int ret = 0;

I don't think this initialization is necessary.

>  	if (chip && chip->setup_irqs)
>  		return chip->setup_irqs(chip, dev, nvec, type);
> @@ -121,9 +121,7 @@ int __weak arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
>  
>  	for_each_pci_msi_entry(entry, dev) {
>  		ret = arch_setup_msi_irq(dev, entry);
> -		if (ret < 0)
> -			return ret;
> -		if (ret > 0)
> +		if (ret)
>  			return -ENOSPC;
>  	}
>  
> -- 
> 2.3.7
> 
> 
> --
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