From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755458AbdEEDlL convert rfc822-to-8bit (ORCPT ); Thu, 4 May 2017 23:41:11 -0400 Received: from smtp.csie.ntu.edu.tw ([140.112.30.61]:38236 "EHLO smtp.csie.ntu.edu.tw" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752496AbdEEDkm (ORCPT ); Thu, 4 May 2017 23:40:42 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170504114858.9008-1-icenowy@aosc.io> <20170504114858.9008-9-icenowy@aosc.io> <20170504130535.6nokhni5a3uxwy66@lukather> From: Chen-Yu Tsai Date: Fri, 5 May 2017 11:40:17 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [linux-sunxi] Re: [PATCH v6 08/13] drm/sun4i: add support for Allwinner DE2 mixers To: Icenowy Zheng Cc: Maxime Ripard , Rob Herring , Chen-Yu Tsai , linux-clk , devicetree , linux-arm-kernel , linux-kernel , dri-devel , linux-sunxi Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 5, 2017 at 12:52 AM, wrote: > 在 2017-05-04 21:05，Maxime Ripard 写道： >> >> On Thu, May 04, 2017 at 07:48:53PM +0800, Icenowy Zheng wrote: >>> >>> Allwinner have a new "Display Engine 2.0" in their new SoCs, which comes >>> with mixers to do graphic processing and feed data to TCON, like the old >>> backends and frontends. >>> >>> Add support for the mixer on Allwinner V3s SoC; it's the simplest one. >>> >>> Currently a lot of functions are still missing -- more investigations >>> are needed to gain enough information for them. >>> >>> Signed-off-by: Icenowy Zheng >>> --- >>> Changes in v6: >>> - Rebased on wens's multi-pipeline patchset. >>> Changes in v5: >>> - Changed some code alignment. >>> - Request real 32-bit DMA (prepare for 64-bit SoCs). >>> Changes in v4: >>> - Killed some dead code according to Jernej. >>> >>> drivers/gpu/drm/sun4i/Kconfig | 10 + >>> drivers/gpu/drm/sun4i/Makefile | 3 + >>> drivers/gpu/drm/sun4i/sun8i_layer.c | 140 +++++++++++++ >>> drivers/gpu/drm/sun4i/sun8i_layer.h | 36 ++++ >>> drivers/gpu/drm/sun4i/sun8i_mixer.c | 394 >>> ++++++++++++++++++++++++++++++++++++ >>> drivers/gpu/drm/sun4i/sun8i_mixer.h | 137 +++++++++++++ >>> 6 files changed, 720 insertions(+) >>> create mode 100644 drivers/gpu/drm/sun4i/sun8i_layer.c >>> create mode 100644 drivers/gpu/drm/sun4i/sun8i_layer.h >>> create mode 100644 drivers/gpu/drm/sun4i/sun8i_mixer.c >>> create mode 100644 drivers/gpu/drm/sun4i/sun8i_mixer.h >>> [...] >>> diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c >>> b/drivers/gpu/drm/sun4i/sun8i_mixer.c >>> new file mode 100644 >>> index 000000000000..e216b84d5bb2 >>> --- /dev/null >>> +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c >>> @@ -0,0 +1,394 @@ [...] >>> + list_add_tail(&mixer->engine.list, &drv->engine_list); >> >> >> You didn't call INIT_LIST_HEAD on that list. > > > So didn't the sun4i_backend driver... > > I think the mixer->engine.list only means an item in the > engine_list, and the drv->engine_list is initialized in the > sun4i_drv source code. I read [1] that if the item is subsequently added to a list, you could omit the INIT_LIST_HEAD call. Makes sense, though you have to be sure you aren't doing anything else with the list element. ChenYu [1] https://isis.poly.edu/kulesh/stuff/src/klist/