linux-kernel - Re: Device driver memory 'mmap()' function helper cleanup

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Message-Id: <201304171115.51509.arnd@arndb.de>
Date:	Wed, 17 Apr 2013 11:15:51 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Clemens Ladisch <clemens@...isch.de>,
	Takashi Iwai <tiwai@...e.de>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: Re: Device driver memory 'mmap()' function helper cleanup

On Wednesday 17 April 2013, Linus Torvalds wrote:
> Anyway, I'm attaching the untested patch to several drivers. Guys,
> mind taking a look? The point here is to simplify the interface,
> avoiding bugs, but also:
> 
>  5 files changed, 21 insertions(+), 87 deletions(-)
> 
> it needs current -git for the new helper function.
> 
> NOTE! The driver subsystem .mmap functions seem to almost universally do
> 
>     if (io_remap_pfn_range(..))
>         return -EAGAIN;
>     return 0;

I took a look at the hpet_mmap function, which still contains this check:

        if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
                return -EINVAL;

As far as I can tell, this check is implied by the new code in
vm_iomap_memory as the len argument passed here is PAGE_SIZE, so you
can remove another three lines in hpet_mmap.

	Arnd
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