From: Arnd Bergmann <arnd@arndb.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: Device driver memory 'mmap()' function helper cleanup
Date: Wed, 17 Apr 2013 11:15:51 +0200
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Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Clemens Ladisch <clemens@ladisch.de>, Takashi Iwai <tiwai@suse.de>,
        Mauro Carvalho Chehab <mchehab@redhat.com>
References: <CA+55aFyK2EEPuBPrqu3AGRbW+8TdP=kLLz4opvynNRcrSWC2ww@mail.gmail.com>
In-Reply-To: <CA+55aFyK2EEPuBPrqu3AGRbW+8TdP=kLLz4opvynNRcrSWC2ww@mail.gmail.com>
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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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