linux-kernel - Re: [PATCH v1 05/47] pci: add pci_iomap

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Date:	Fri, 27 Mar 2015 19:40:26 +0100
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>, luto@...capital.net,
	mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
	jgross@...e.com, JBeulich@...e.com, bp@...e.de,
	suresh.b.siddha@...el.com, venkatesh.pallipadi@...el.com,
	airlied@...hat.com, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org, x86@...nel.org,
	xen-devel@...ts.xenproject.org, Ingo Molnar <mingo@...e.hu>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Antonino Daplas <adaplas@...il.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Stefan Bader <stefan.bader@...onical.com>,
	ville.syrjala@...ux.intel.com, david.vrabel@...rix.com,
	toshi.kani@...com,
	Roger Pau Monné <roger.pau@...rix.com>,
	xen-devel@...ts.xensource.com
Subject: Re: [PATCH v1 05/47] pci: add pci_iomap_wc() variants

On Wed, Mar 25, 2015 at 04:07:43PM -0400, Konrad Rzeszutek Wilk wrote:
> On Fri, Mar 20, 2015 at 04:17:55PM -0700, Luis R. Rodriguez wrote:
> > From: "Luis R. Rodriguez" <mcgrof@...e.com>
> > 
> > This allows drivers to take advantage of write-combining
> > when possible. Ideally we'd have pci_read_bases() just
> > peg an IORESOURCE_WC flag for us but where exactly
> > video devices memory lie varies *largely* and at times things
> > are mixed with MMIO registers, sometimes we can address
> > the changes in drivers, other times the change requires
> > intrusive changes.
> > 
> > Although there is also arch_phys_wc_add() that makes use of
> > architecture specific write-combinging alternatives (MTRR on
> 
> combinging?

Amended.

> > diff --git a/lib/pci_iomap.c b/lib/pci_iomap.c
> > index bcce5f1..30b65ae 100644
> > --- a/lib/pci_iomap.c
> > +++ b/lib/pci_iomap.c
> > @@ -52,6 +52,46 @@ void __iomem *pci_iomap_range(struct pci_dev *dev,
> >  EXPORT_SYMBOL(pci_iomap_range);
> >  
> >  /**
> > + * pci_iomap_wc_range - create a virtual WC mapping cookie for a PCI BAR
> > + * @dev: PCI device that owns the BAR
> > + * @bar: BAR number
> > + * @offset: map memory at the given offset in BAR
> > + * @maxlen: max length of the memory to map
> > + *
> > + * Using this function you will get a __iomem address to your device BAR.
> > + * You can access it using ioread*() and iowrite*(). These functions hide
> > + * the details if this is a MMIO or PIO address space and will just do what
> > + * you expect from them in the correct way. When possible write combining
> > + * is used.
> > + *
> > + * @maxlen specifies the maximum length to map. If you want to get access to
> > + * the complete BAR from offset to the end, pass %0 here.
> 
> s/%0/0 ? Or is that some special syntax?

This copies the syntax of pci_iomap_range() which also uses %0, and as per
Documentation/kernel-doc-nano-HOWTO.txt % is used for constants. See:

scripts/kernel-doc -man -function pci_iomap_range lib/pci_iomap.c | nroff -man | less

  Luis
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