linux-kernel - Re: [PATCH] Clarify pci_iomap() usage for MMIO-only devices

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Date:	Tue, 18 Sep 2007 14:46:40 -0400
From:	"Luis R. Rodriguez" <mcgrof@...il.com>
To:	"Alan Cox" <alan@...rguk.ukuu.org.uk>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Jeff Garzik" <jeff@...zik.org>,
	"John W. Linville" <linville@...driver.com>,
	linux-wireless <linux-wireless@...r.kernel.org>
Subject: Re: [PATCH] Clarify pci_iomap() usage for MMIO-only devices

On 9/18/07, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> On Mon, 17 Sep 2007 16:22:07 -0400
> "Luis R. Rodriguez" <mcgrof@...il.com> wrote:
>
> > This patch updates the pci_iomap() kernel-doc to make it clarify the
> > case when read*()/write*() can be called over ioread*/iowrite*(). When
> > driver writers read this documenation sometimes it is assumed you just
> > *need* to use ioread*()/iorwrite*(). We have an exception so lets just
> > clarify this is not true for the exception.
> >
> >  lib/iomap.c |   11 ++++++++---
> >  1 files changed, 8 insertions(+), 3 deletions(-)
> >
> > Signed-off-by: Luis R. Rodriguez <mcgrof@...il.com>
>
> Reviewed-by: Alan Cox <alan@...hat.com>
>
> Although I would say s/recommended/required/

Alright, here is the same patch inline with s/recommended/required/ language:

Signed-off-by: Luis R. Rodriguez <mcgrof@...il.com>

  Luis

---
 lib/iomap.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/lib/iomap.c b/lib/iomap.c
index 864f2ec..33651f8 100644
--- a/lib/iomap.c
+++ b/lib/iomap.c
@@ -247,9 +247,14 @@ EXPORT_SYMBOL(ioport_unmap);
  * @maxlen: 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.
+ * If you use pci_iomap() it is recommended you use ioread*() and
iowrite*(). If
+ * your device is MMIO-only and as long as future architectures don't break the
+ * assumption that pcio_iomap()-returned cookie can be used by read*()/write*()
+ * then you can use read*()/write*() instead. The ioread*() and iowrite*()
+ * 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. Drivers for MMIO-only
+ * devices would use this only to save themselves from having to call
+ * &pci_resource_start().
  *
  * @maxlen specifies the maximum length to map. If you want to get access to
  * the complete BAR without checking for its length first, pass %0 here.
-
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