From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Subject: Re: [Linux-c6x-dev] [PATCH 3/9] c6x: Provide dma_mmap_coherent()
 and dma_get_sgtable()
Date: Tue, 15 Jan 2013 09:46:58 +0530
Message-ID: <50F4D83A.7020803@synopsys.com>
References: <1358073890-3610-1-git-send-email-geert@linux-m68k.org>  <1358073890-3610-3-git-send-email-geert@linux-m68k.org> <1358177872.4357.53.camel@t520.localdomain>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-7
Content-Transfer-Encoding: QUOTED-PRINTABLE
Return-path: <linux-arch-owner@vger.kernel.org>
Received: from hermes.synopsys.com ([198.182.44.81]:58183 "EHLO
	hermes.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752011Ab3AOERN (ORCPT
	<rfc822;linux-arch@vger.kernel.org>); Mon, 14 Jan 2013 23:17:13 -0500
In-Reply-To: <1358177872.4357.53.camel@t520.localdomain>
Sender: linux-arch-owner@vger.kernel.org
List-ID: <linux-arch.vger.kernel.org>
To: Mark Salter <msalter@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>, linux-arch@vger.kernel.org, linux-c6x-dev@linux-c6x.org, linux-kernel@vger.kernel.org, Marek Szyprowski <m.szyprowski@samsung.com>

On Monday 14 January 2013 09:07 PM, Mark Salter wrote:
> On Sun, 2013-01-13 at 11:44 +0100, Geert Uytterhoeven wrote:
>> c6x/allmodconfig (assumed):
>>
>> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function =A1vb2_d=
c_mmap=A2:
>> drivers/media/v4l2-core/videobuf2-dma-contig.c:204: error: implicit =
declaration of function =A1dma_mmap_coherent=A2
>> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function =A1vb2_d=
c_get_base_sgt=A2:
>> drivers/media/v4l2-core/videobuf2-dma-contig.c:387: error: implicit =
declaration of function =A1dma_get_sgtable=A2
>>
>> For architectures using dma_map_ops, dma_mmap_coherent() and
>> dma_get_sgtable() are provided in <asm-generic/dma-mapping-common.h>=
=2E
>>
>> C6x does not use dma_map_ops, hence it should implement them as inli=
ne
>> stubs using dma_common_mmap() and dma_common_get_sgtable().
>>
>=20
> So are dma_mmap_coherent() and dma_get_sgtable() part of the DMA API
> now? I don't them in Documentation/DMA*.txt anywhere.
>=20
> Why does the default dma_common_mmap() for !CONFIG_MMU return an
> error?
>=20
> Wouldn't it be better to provide default implementations that an arch
> could override rather than having to patch all "no dma_map_ops"
> architectures?
>=20
> --Mark
>=20
>=20

Speaking for the still-reviewed ARC Port, I completely agree with Mark.

-Vineet