linux-kernel - Re: [PATCH] powerpc/npu-dma: Remove NPU DMA ops

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Message-ID: <87wopziila.fsf@concordia.ellerman.id.au>
Date:   Wed, 31 Oct 2018 02:01:53 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christoph Hellwig <hch@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Christoph Hellwig <hch@....de>,
        Alistair Popple <alistair@...ple.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/npu-dma: Remove NPU DMA ops

Christoph Hellwig <hch@....de> writes:

> On Wed, Oct 31, 2018 at 12:09:29AM +1100, Benjamin Herrenschmidt wrote:
>> On Tue, 2018-10-30 at 13:58 +0100, Christoph Hellwig wrote:
>> > Please take my patch instead.  We have a kernel polcity to not keep
>> > dead code around, and everyone including Linus and the attending IBMers
>> > confirmed this.
>> 
>> Let's call a cat a cat ... ;-)
>> 
>> It's not *dead* code. It's code that is used by an out of tree driver
>> (which also happen not to be open source).

(Actually that part of the driver is MIT licensed, but yes other parts
 are not open source.)

> Which clearly makes it a derived work of the kernel if it uses an
> interface just create for it, and thus even more important to remove
> it to not get anyone into legal trouble.

We don't want driver code calling into firmware, that's the job of
platform code, so we would need the same API (or something similar) for
a GPL driver.

cheers