From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: Tom Brown <sa212+emis@cyconix.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Yong Zhang <yong.zhang@windriver.com>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: Question: how to copy to user space from a tasklet
Date: Mon, 18 Oct 2010 19:01:22 +0200 [thread overview]
Message-ID: <4CBC7D62.6040408@s5r6.in-berlin.de> (raw)
In-Reply-To: <4CBC6BA0.60507@cyconix.com>
Tom Brown wrote:
> Thanks, think I'm there:
>
> 1 - The user calls mmap() with a specific offset to flag that he wants a
> DMA buffer
>
> 2 - I then 'vmalloc' the buffer, and call 'setPageReserved' for each page
>
> I then step over each page, and:
>
> 3 - call 'vmalloc_to_pfn' to get a PFN for each page, and then
>
> 4 - call 'remap_page_range' for that page (I instead call
> 'remap_pfn_range' for kernels >= 2.6.10, but I'm on 2.6.9)
>
> This gives me the buffer, and the interrupt handler then just uses
> 'memcpy' to copy data to the user.
I would have thought of a bunch of alloc_page() and vm_insert_page() but I
don't know if vm_insert_page exists in 2.6.9 and if it honors user limits.
Plus dma_map_page() to get zero-copy operation with a DMA capable device.
--
Stefan Richter
-=====-==-=- =-=- =--=-
http://arcgraph.de/sr/
next prev parent reply other threads:[~2010-10-18 17:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-14 10:43 Tom Brown
2010-10-15 2:15 ` Yong Zhang
2010-10-15 5:57 ` Stefan Richter
2010-10-15 8:59 ` Arnd Bergmann
2010-10-18 15:45 ` Tom Brown
2010-10-18 17:01 ` Stefan Richter [this message]
2010-10-18 18:02 ` Tom Brown
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