linux-kernel - Re: [PATCH] xtensa: Fix mmap() support

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Message-ID: <20170330084555.GA13310@infradead.org>
Date:   Thu, 30 Mar 2017 01:45:55 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Max Filippov <jcmvbkbc@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Chris Zankel <chris@...kel.net>,
        "linux-xtensa@...ux-xtensa.org" <linux-xtensa@...ux-xtensa.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xtensa: Fix mmap() support

On Thu, Mar 30, 2017 at 10:30:32AM +0200, Boris Brezillon wrote:
> I think I misunderstood what CONFIG_ARCH_NO_COHERENT_DMA_MMAP means.
> My understanding was that, if CONFIG_ARCH_NO_COHERENT_DMA_MMAP is not
> set, the architecture is assumed to be cache-coherent, but re-reading
> the option name I realize you're probably right.

It just says that the architecture did not support dma_common_mmap at
the point in time when I switched all architectures to use the common
dma_ops or implementing the various dma calls.  There is no inherent
logic behind the symbol, and if the few remaining architectures could
support it with a bit work the option could just go away.