linux-kernel - Re: [PATCH] m32r: add simple dma

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Message-Id: <20161020202918.b7cb3fe24058addddabb7534@linux-foundation.org>
Date:   Thu, 20 Oct 2016 20:29:18 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:     linux-kernel@...r.kernel.org, fengguang.wu@...el.com
Subject: Re: [PATCH] m32r: add simple dma

On Sat,  8 Oct 2016 23:23:18 +0530 Sudip Mukherjee <sudipm.mukherjee@...il.com> wrote:

> Some builds of m32r were failing as it tried to build few drivers which
> needed dma but m32r is not having dma support. Objections were raised
> when it was tried to make those drivers depend on HAS_DMA.

Huh.  What were these objections?  That sounds like the appropriate
fix.  And I suggest that a summary of those objections be captured in
this patch's changelog.

> So the next
> best thing is to add dma support to m32r.
> dma_noop is a very simple dma with 1:1 memory mapping.
> 
> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
> ---
> 
> Hi Andrew,
> Just to let you know that this was not tested on any board. I think I
> have told you earlier that inspite of all  my efforts I could not find
>  any source of information to procure a board of m32r.

It is a worry.  We're saying "m32r linux now supports these drivers",
only we don't know if that is true.

> Hi Fengguang,
> If Andrew accepts this patch then it will open pandora's box as lots of
> other drivers which were never build for m32r will be built now and you
> are going to gets lots and lots of new build warnings. But nothing
> breaks.