linux-kernel - [PATCH] UIO: Allow a UIO driver to override the default pgprot when we mmap

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Message-Id: <1318430616-20351-1-git-send-email-galak@kernel.crashing.org>
Date:	Wed, 12 Oct 2011 09:43:36 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	hjk@...sjkoch.de
Cc:	gregkh@...e.de, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] UIO: Allow a UIO driver to override the default pgprot when we mmap

For some devices the default behavior of pgprot_noncached is not
the correct flags for the address space.  Provide a means for the
kernel side UIO driver to override the flags without having to
implement its own full mmap callback.

Signed-off-by: Kumar Gala <galak@...nel.crashing.org>
---
 drivers/uio/uio.c          |    6 +++++-
 include/linux/uio_driver.h |    2 ++
 2 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index d2efe82..88f4444 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -656,7 +656,11 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
 
 	vma->vm_flags |= VM_IO | VM_RESERVED;
 
-	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	if (idev->info->mem[mi].set_pgprot)
+		vma->vm_page_prot =
+			idev->info->mem[mi].set_pgprot(vma->vm_page_prot);
+	else
+		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
 	return remap_pfn_range(vma,
 			       vma->vm_start,
diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
index 665517c..4c618cd 100644
--- a/include/linux/uio_driver.h
+++ b/include/linux/uio_driver.h
@@ -28,6 +28,7 @@ struct uio_map;
  * @memtype:		type of memory addr points to
  * @internal_addr:	ioremap-ped version of addr, for driver internal use
  * @map:		for use by the UIO core only.
+ * @set_pgprot:		allow driver to override default(noncached) pgprot
  */
 struct uio_mem {
 	const char		*name;
@@ -36,6 +37,7 @@ struct uio_mem {
 	int			memtype;
 	void __iomem		*internal_addr;
 	struct uio_map		*map;
+	pgprot_t (*set_pgprot)(pgprot_t prot);
 };
 
 #define MAX_UIO_MAPS	5
-- 
1.7.3.4

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