linux-kernel - Re: [PATCH v11 24/27] iommu/exynos: use exynos-iommu specific typedef

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Message-id: <20140320185519.0035bf69004da6c570133414@samsung.com>
Date:	Thu, 20 Mar 2014 18:55:19 +0900
From:	Cho KyongHo <pullip.cho@...sung.com>
To:	Grant Grundler <grundler@...omium.org>
Cc:	Linux ARM Kernel <linux-arm-kernel@...ts.infradead.org>,
	Linux DeviceTree <devicetree@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>,
	Antonios Motakis <a.motakis@...tualopensystems.com>,
	Joerg Roedel <joro@...tes.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Prathyush <prathyush.k@...sung.com>,
	Rahul Sharma <rahul.sharma@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Tomasz Figa <t.figa@...sung.com>,
	Varun Sethi <Varun.Sethi@...escale.com>
Subject: Re: [PATCH v11 24/27] iommu/exynos: use exynos-iommu specific typedef

On Tue, 18 Mar 2014 18:33:20 -0700, Grant Grundler wrote:
> On Thu, Mar 13, 2014 at 10:13 PM, Cho KyongHo <pullip.cho@...sung.com> wrote:
> > This commit introduces sysmmu_pte_t for page table entries and
> > sysmmu_iova_t vor I/O virtual address that is manipulated by
> > exynos-iommu driver. The purpose of the typedef is to remove
> > dependencies to the driver code from the change of CPU architecture
> > from 32 bit to 64 bit.
> 
> hi Cho,
> I noticed this before but understood this code was only compiled for
> ILP-32 programming model. I'm assuming that is going to change in the
> not-to-distant future. Good. :)
> 

Thanks.

> >
> > Signed-off-by: Cho KyongHo <pullip.cho@...sung.com>
> > ---
> >  drivers/iommu/exynos-iommu.c |  103 ++++++++++++++++++++++--------------------
> >  1 file changed, 54 insertions(+), 49 deletions(-)
> >
> > diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c
> > index e375501..6e716cc 100644
> > --- a/drivers/iommu/exynos-iommu.c
> > +++ b/drivers/iommu/exynos-iommu.c
> > @@ -56,19 +56,19 @@
> >  #define lv2ent_large(pent) ((*(pent) & 3) == 1)
> >
> >  #define section_phys(sent) (*(sent) & SECT_MASK)
> > -#define section_offs(iova) ((iova) & 0xFFFFF)
> > +#define section_offs(iova) ((sysmmu_iova_t)(iova) & 0xFFFFF)
> 
> The cast will mask abuses of iova. Define section_offs as a static
> function and GCC can type check iova parameter to make sure it's a
> sysmmu_iova_t.
> Thoughts?
> 
> I was thinking "((iova) & (sysmmu_iova_t) 0XFFFFF)" might do what you
> want but it doesn't warn on abuse that I tried. I believe GCC knows
> the upper bits are being ignored.

Thank you for advice.

I agree that type checking by compiler will be more helpful
as you mentioned.

Regards,

KyongHo
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