linux-kernel - RE: [PATCH 1/3] iommu/fsl: Factor out PCI specific code.

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Message-ID: <C5ECD7A89D1DC44195F34B25E172658D0A53D863@039-SN2MPN1-013.039d.mgd.msft.net>
Date:	Tue, 15 Oct 2013 14:35:41 +0000
From:	Sethi Varun-B16395 <B16395@...escale.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Yoder Stuart-B08248 <B08248@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Bhushan Bharat-R65777 <R65777@...escale.com>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [PATCH 1/3] iommu/fsl: Factor out PCI specific code.



> -----Original Message-----
> From: iommu-bounces@...ts.linux-foundation.org [mailto:iommu-
> bounces@...ts.linux-foundation.org] On Behalf Of Bjorn Helgaas
> Sent: Tuesday, October 15, 2013 5:46 AM
> To: Sethi Varun-B16395
> Cc: Yoder Stuart-B08248; linux-kernel@...r.kernel.org; iommu@...ts.linux-
> foundation.org; Bhushan Bharat-R65777; Wood Scott-B07421; linuxppc-
> dev@...ts.ozlabs.org
> Subject: Re: [PATCH 1/3] iommu/fsl: Factor out PCI specific code.
> 
> On Sun, Oct 13, 2013 at 02:02:32AM +0530, Varun Sethi wrote:
> > Factor out PCI specific code in the PAMU driver.
> >
> > Signed-off-by: Varun Sethi <Varun.Sethi@...escale.com>
> > ---
> >  drivers/iommu/fsl_pamu_domain.c |   81 +++++++++++++++++++------------
> --------
> >  1 file changed, 40 insertions(+), 41 deletions(-)
> >
> > diff --git a/drivers/iommu/fsl_pamu_domain.c
> > b/drivers/iommu/fsl_pamu_domain.c index c857c30..e02e1de 100644
> > --- a/drivers/iommu/fsl_pamu_domain.c
> > +++ b/drivers/iommu/fsl_pamu_domain.c
> > @@ -677,13 +677,9 @@ static int handle_attach_device(struct
> fsl_dma_domain *dma_domain,
> >  	return ret;
> >  }
> >
> > -static int fsl_pamu_attach_device(struct iommu_domain *domain,
> > -				  struct device *dev)
> > +static void check_for_pci_dma_device(struct device **dev)
> 
> "check_for_pci_dma_device()" doesn't give a good clue about what the
> function returns.  And why return something via a reference parameter
> when you could return it directly?
[Sethi Varun-B16395] I will rename the function to get_dma_device and make it return a pointer.
> 
> >  {
> > -	struct fsl_dma_domain *dma_domain = domain->priv;
> > -	const u32 *liodn;
> > -	u32 liodn_cnt;
> > -	int len, ret = 0;
> > +#ifdef CONFIG_PCI
> >  	struct pci_dev *pdev = NULL;
> >  	struct pci_controller *pci_ctl;
> 
> This is sort of a goofy looking function.  It would read much better as
> something like this:
> 
[Sethi Varun-B16395] Will make the change.

>       struct device *dma_dev = dev;
> 
>   #ifdef CONFIG_PCI
>       if (...) {
>           dma_dev = ...;
>       }
>   #endif
> 
>       return dma_dev;
> 
> Does this need to care about reference counting when you return a pointer
> to a different device?
> 
[Sethi Varun-B16395] Reference counting isn't required, as we are just obtaining the LIODN value from the PCI controller.

-Varun

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