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

Hans J. Koch
2011-10-12T15:35:55Z

On Wed, Oct 12, 2011 at 09:43:36AM -0500, Kumar Gala wrote:
> For some devices the default behavior of pgprot_noncached is not
> the correct flags for the address space.

For what devices? Can you give a real world usecase where this is needed?

Thanks,
Hans

> 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@kernel.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
>
>