linux-kernel - Re: UIO: phys_mem_access

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Message-ID: <20080513185137.GA3342@local>
Date:	Tue, 13 May 2008 20:51:38 +0200
From:	"Hans J. Koch" <hjk@...utronix.de>
To:	Johann Baudy <johaahn@...il.com>
Cc:	hjk@...utronix.de, gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: UIO: phys_mem_access_prot() miss?

On Tue, May 13, 2008 at 03:55:29PM +0200, Johann Baudy wrote:
> Hi Hans, Greg,
> 
> I need some help on UIO driver.
> I have to add this below workaround (in uio.c) to be able to access
> phys memory from user space.
> I'm currently using PPC arch.
> Am I wrong? or Is it a miss?
> 
> static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
> {
> 
> ...
> 	switch (idev->info->mem[mi].memtype) {
> 		case UIO_MEM_PHYS:
> +       	vma->vm_page_prot = phys_mem_access_prot(filep,
> +            idev->info->mem[mi].addr >> PAGE_SHIFT,
> +						 vma->vm_end - vma->vm_start,
> +						 vma->vm_page_prot);
> 			return uio_mmap_physical(vma);
> 		case UIO_MEM_LOGICAL:
> ...
> 
> }
> 
> FYI: I've copied those lines from mem char driver in mmap_mem().

Hi Johann,
what kernel are you using? Similar problems were reported before, and
we've already applied a patch that should fix it. I think it hit
mainline shortly before the 2.6.25 release. uio_mmap() should work with
kernels >= 2.6.25 for PPC.

Thanks,
Hans

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