linux-kernel - Re: GPL question: using large contiguous memory in proprietary driver.

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Date:	Wed, 15 Oct 2008 09:54:28 -0400
From:	Mark Hounschell <markh@...pro.net>
To:	Kaz Kylheku <kkylheku@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: GPL question: using large contiguous memory in proprietary driver.

Kaz Kylheku wrote:
> Hi all,
> 
> I have the following question. Suppose that some proprietary driver
> (otherwise completely clean, based only on non-GPL symbols)
> requires a large buffer of physically contiguous memory.
> 
> A GPL-ed driver could get this memory by having some boot-time
> code compiled into the kernel which calls bootmem_alloc during
> kernel initialization. This function would stash the address of the
> memory into some global variable which is exported for the
> module to use.
> 
> How do you solve this problem in a proprietary driver? It seems
> like the above solution taints the kernel, because the kernel
> provides a symbol which exists only for the sake of supporting
> a proprietary driver.
> 
> Would it be okay to have a mechanism like this:
> Suppose that  on the kernel command line, you could
> request a boot-time memory allocation and give it a name.
> For instance, the parameter:
> 
>    boot_alloc=foo,8192K
> 
> would create an 8192 kilobyte allocation, and associate it
> with the string "foo".   A non-GPL function would be provided to
> find the address of this memory, using the string "foo"
> as the key. The proprietary driver would document the
> requirement that it needs a memory region of at least
> 8192K, under the name "foo".
> 
> Help! :)

Hardware with scatter/gatcher capabilites would be best. But short
of that, you could just use the bigphysarea patch. GOOGLE for it and you'll
find a version suitable for most kernel versions. I've been using it for years with
a GPL driver but even if the driver wasn't GPL I would still be using it.

I sure wish it could be included in the kernel??

There really aren't many good reasons not to GPL your driver BTW.

Mark
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