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From: David Woodhouse <dwmw2@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH 1/3] arm64: enable pci resource mapping using sysfs
Date: Wed, 15 Mar 2017 19:18:16 +0000	[thread overview]
Message-ID: <1489605496.4195.182.camel@infradead.org> (raw)
In-Reply-To: <20170315175353.GA29452@leverpostej>

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On Wed, 2017-03-15 at 17:54 +0000, Mark Rutland wrote:
> It's not so much "broken" as "not currently supported".

Yeah, I thought that when I inherited the commit, but didn't get as far
as rephrasing it. Will do so.

> [...]
> 
> > 
> > +#define HAVE_PCI_MMAP
> > +extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
> > +			       enum pci_mmap_state mmap_state, int write_combine);
> > +
> Per the prior attempt at this [1], we only want to expose the sysfs
> interface, and not the legacy procfs interface, and need the two
> decoupled [2].

I do not like that idea. The procfs horridness is legacy, sure, but
it's not actually an arch-specific interface. You get to mess with
'legacy' syscalls all you like on a new architecture, but there could
exist arch-agnostic code which uses the procfs interface, surely?

> > +	if (write_combine)
> > +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> > +	else
> > +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> ... as per Will's comment in [3], the latter of these should use
> pgprot_device.

Will fix that; thanks.

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WARNING: multiple messages have this Message-ID (diff)
From: dwmw2@infradead.org (David Woodhouse)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 1/3] arm64: enable pci resource mapping using sysfs
Date: Wed, 15 Mar 2017 19:18:16 +0000	[thread overview]
Message-ID: <1489605496.4195.182.camel@infradead.org> (raw)
In-Reply-To: <20170315175353.GA29452@leverpostej>

On Wed, 2017-03-15 at 17:54 +0000, Mark Rutland wrote:
> It's not so much "broken" as "not currently supported".

Yeah, I thought that when I inherited the commit, but didn't get as far
as rephrasing it. Will do so.

> [...]
> 
> > 
> > +#define HAVE_PCI_MMAP
> > +extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
> > +			???????enum pci_mmap_state mmap_state, int write_combine);
> > +
> Per the prior attempt at this [1], we only want to expose the sysfs
> interface, and not the legacy procfs interface, and need the two
> decoupled [2].

I do not like that idea. The procfs horridness is legacy, sure, but
it's not actually an arch-specific interface. You get to mess with
'legacy' syscalls all you like on a new architecture, but there could
exist arch-agnostic code which uses the procfs interface, surely?

> > +	if (write_combine)
> > +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> > +	else
> > +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> ... as per Will's comment in [3], the latter of these should use
> pgprot_device.

Will fix that; thanks.
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  reply	other threads:[~2017-03-15 19:18 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-15 17:17 [PATCH 1/3] arm64: enable pci resource mapping using sysfs David Woodhouse
2017-03-15 17:17 ` David Woodhouse
2017-03-15 17:17 ` David Woodhouse
2017-03-15 17:54 ` Mark Rutland
2017-03-15 17:54   ` Mark Rutland
2017-03-15 19:18   ` David Woodhouse [this message]
2017-03-15 19:18     ` David Woodhouse
2017-03-20 10:24     ` Will Deacon
2017-03-20 10:24       ` Will Deacon
2017-03-20 10:28       ` David Woodhouse
2017-03-20 10:28         ` David Woodhouse

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