linux-kernel - Re: [PATCH 1/5] uio: Add new UIO_MEM_PHYS

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Date:	Tue, 9 Sep 2014 12:29:10 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Ankit Jindal <ankit.jindal@...aro.org>
Cc:	linux-kernel@...r.kernel.org, "Hans J. Koch" <hjk@...sjkoch.de>,
	patches@....com, linux-arm-kernel@...ts.infradead.org,
	Rob Herring <robh+dt@...nel.org>,
	Tushar Jagad <tushar.jagad@...aro.org>
Subject: Re: [PATCH 1/5] uio: Add new UIO_MEM_PHYS_CACHE type for mem regions

On Tue, Sep 09, 2014 at 03:26:55PM +0530, Ankit Jindal wrote:
> Currently, three types of mem regions are supported: UIO_MEM_PHYS,
> UIO_MEM_LOGICAL and UIO_MEM_VIRTUAL. Among these UIO_MEM_PHYS helps
> UIO driver export physcial memory to user space as non-cacheable
> user memory. Typcially memory-mapped registers of a device are exported
> to user space as UIO_MEM_PHYS type mem region. The UIO_MEM_PHYS type
> is not useful if dma-capable devices are capable of maintaining coherency
> with CPU caches becasue we can allow cacheable access to memory shared
> between such devices and user space.
> 
> This patch adds new type UIO_MEM_PHYS_CACHE for mem regions to enable
> cacheable access to physical memory from user space.
> 
> Signed-off-by: Ankit Jindal <ankit.jindal@...aro.org>
> Signed-off-by: Tushar Jagad <tushar.jagad@...aro.org>
> ---
>  drivers/uio/uio.c          |   22 +++++++++++++---------
>  include/linux/uio_driver.h |    7 ++++---
>  2 files changed, 17 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index a673e5b..ff5b6c0 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -644,7 +644,7 @@ static const struct vm_operations_struct uio_physical_vm_ops = {
>  #endif
>  };
>  
> -static int uio_mmap_physical(struct vm_area_struct *vma)
> +static int uio_mmap_physical(struct vm_area_struct *vma, bool cacheable)
>  {
>  	struct uio_device *idev = vma->vm_private_data;
>  	int mi = uio_find_mem_index(vma);
> @@ -659,7 +659,9 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
>  		return -EINVAL;
>  
>  	vma->vm_ops = &uio_physical_vm_ops;
> -	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> +
> +	if (!cacheable)
> +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>  
>  	/*
>  	 * We cannot use the vm_iomap_memory() helper here,
> @@ -706,13 +708,15 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
>  	}
>  
>  	switch (idev->info->mem[mi].memtype) {
> -		case UIO_MEM_PHYS:
> -			return uio_mmap_physical(vma);
> -		case UIO_MEM_LOGICAL:
> -		case UIO_MEM_VIRTUAL:
> -			return uio_mmap_logical(vma);
> -		default:
> -			return -EINVAL;
> +	case UIO_MEM_PHYS:
> +		return uio_mmap_physical(vma, false);
> +	case UIO_MEM_LOGICAL:
> +	case UIO_MEM_VIRTUAL:
> +		return uio_mmap_logical(vma);
> +	case UIO_MEM_PHYS_CACHE:
> +		return uio_mmap_physical(vma, true);
> +	default:
> +		return -EINVAL;

Please don't do code style cleanups in the same patch you are adding new
functionality.  I can't take this because of this, sorry.

greg k-h
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