Re: [PATCH] uio: add UIO_MEM_CUSTOM support

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Feb 15, 2017 at 12:43:06PM +0800, lixiubo@cmss.chinamobile.com wrote:
> From: Xiubo Li <lixiubo@cmss.chinamobile.com>
> 
> This will allow UIO based drivers, like TCMU, have opportunities to
> implement their own mmap magics.
> 
> Signed-off-by: Xiubo Li <lixiubo@cmss.chinamobile.com>
> ---
>  drivers/uio/uio.c          | 2 ++
>  include/linux/uio_driver.h | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index fba021f..6ca0ae0 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -708,6 +708,8 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
>  		case UIO_MEM_LOGICAL:
>  		case UIO_MEM_VIRTUAL:
>  			return uio_mmap_logical(vma);
> +		case UIO_MEM_CUSTOM:
> +			return 0;

How does this help?

Can you provide an update to the documentation in
Documentation/driver-api/uio-howto.rst to show how to use this?

thanks,

greg k-h