Subject: Re: allocation failed: out of vmalloc space error treating and
	VIDEO1394 IOC LISTEN CHANNEL ioctl failed problem
From: Arjan van de Ven <arjan@infradead.org>
To: Kristian =?ISO-8859-1?Q?H=F8gsberg?= <krh@bitplanet.net>
Cc: David Moore <dcm@mit.edu>, linux1394-devel@lists.sourceforge.net,
       theSeinfeld@users.sourceforge.net, Bill Davidsen <davidsen@tmr.com>,
       linux-kernel@vger.kernel.org, libdc1394-devel@lists.sourceforge.net
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Organization: Intel International BV
Date: Mon, 15 Jan 2007 13:24:17 -0800
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> However, what I'd really like to do is to leave it to user space to
> allocate the memory as David describes.  In the transmit case, user
> space allocates memory (malloc or mmap) and loads the payload into
> that buffer.

there is a lot of pain involved with doing things this way, it is a TON
better if YOU provide the memory via a custom mmap handler for a device
driver.
(there are a lot of security nightmares involved with the opposite
model, like the user can put any kind of memory there, even pci mmio
space)

>   Then is does an ioctl() on the firewire control device

ioctls are evil ;) esp an "mmap me" ioctl

> It's not too difficult from what I'm doing now, I'd just like to give
> user space more control over the buffers it uses for streaming (i.e.
> letting user space allocate them).  What I'm missing here is: how do I
> actually pin a page in memory?  I'm sure it's not too difficult, but I
> haven't yet figured it out and I'm sure somebody knows it off the top
> of his head.

again the best way is for you to provide an mmap method... you can then
fill in the pages and keep that in some sort of array; this is for
example also what the DRI/DRM layer does for textures etc...

-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

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