linux-kernel - RE: [PATCH v2 05/12] iommu: Change the return value of dev_iommu

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Date:   Fri, 4 Aug 2023 03:55:30 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Will Deacon" <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 05/12] iommu: Change the return value of
 dev_iommu_get()

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Friday, August 4, 2023 11:10 AM
> 
> On 2023/8/3 15:59, Tian, Kevin wrote:
> >> From: Lu Baolu <baolu.lu@...ux.intel.com>
> >> Sent: Thursday, July 27, 2023 1:49 PM
> >>
> >> Make dev_iommu_get() return 0 for success and error numbers for failure.
> >> This will make the code neat and readable. No functionality changes.
> >>
> >> Reviewed-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> >> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> >> ---
> >>   drivers/iommu/iommu.c | 19 +++++++++++--------
> >>   1 file changed, 11 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> >> index 00309f66153b..4ba3bb692993 100644
> >> --- a/drivers/iommu/iommu.c
> >> +++ b/drivers/iommu/iommu.c
> >> @@ -290,20 +290,20 @@ void iommu_device_unregister(struct
> >> iommu_device *iommu)
> >>   }
> >>   EXPORT_SYMBOL_GPL(iommu_device_unregister);
> >>
> >> -static struct dev_iommu *dev_iommu_get(struct device *dev)
> >> +static int dev_iommu_get(struct device *dev)
> >>   {
> >>   	struct dev_iommu *param = dev->iommu;
> >>
> >>   	if (param)
> >> -		return param;
> >> +		return 0;
> >>
> >>   	param = kzalloc(sizeof(*param), GFP_KERNEL);
> >>   	if (!param)
> >> -		return NULL;
> >> +		return -ENOMEM;
> >>
> >>   	mutex_init(&param->lock);
> >>   	dev->iommu = param;
> >> -	return param;
> >> +	return 0;
> >>   }
> >>
> >
> > Jason's series [1] has been queued. Time to refine according to
> > the discussion in [2].
> >
> > [1] https://lore.kernel.org/linux-iommu/ZLFYXlSBZrlxFpHM@8bytes.org/
> > [2] https://lore.kernel.org/linux-iommu/c815fa2b-00df-91e1-8353-
> 8258773957e4@...ux.intel.com/
> 
> I'm not sure I understand your point here. This only changes the return
> value of dev_iommu_get() to make the code more concise.
> 

I thought the purpose of this patch was to prepare for next patch which
moves dev->fault_param initialization to dev_iommu_get().

with Jason's rework IMHO that initialization more fits in iommu_init_device().

that's my real point. If you still want to clean up dev_iommu_get() it's fine
but then it may not belong to this series. 😊