From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932655AbdELLB6 (ORCPT ); Fri, 12 May 2017 07:01:58 -0400 Received: from galahad.ideasonboard.com ([185.26.127.97]:36634 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757644AbdELLBu (ORCPT ); Fri, 12 May 2017 07:01:50 -0400 From: Laurent Pinchart To: Archit Taneja Cc: dri-devel@lists.freedesktop.org, Jose Abreu , Daniel Vetter , Alexey Brodkin , linux-kernel@vger.kernel.org, Carlos Palminha Subject: Re: [PATCH v2 6/8] drm: Introduce drm_bridge_mode_valid() Date: Fri, 12 May 2017 14:01:49 +0300 Message-ID: <2203839.UYlrXxpDjl@avalon> User-Agent: KMail/4.14.10 (Linux/4.9.16-gentoo; KDE/4.14.29; x86_64; ; ) In-Reply-To: References: <1645078.FS6fmucJTb@avalon> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id v4CB2HTF008835 Hi Archit, On Friday 12 May 2017 16:20:07 Archit Taneja wrote: > On 05/12/2017 03:08 PM, Laurent Pinchart wrote: > > On Wednesday 10 May 2017 17:14:33 Daniel Vetter wrote: > >> On Wed, May 10, 2017 at 04:41:09PM +0300, Ville Syrjälä wrote: > >>> On Tue, May 09, 2017 at 06:00:13PM +0100, Jose Abreu wrote: > >>>> Introduce a new helper function which calls mode_valid() callback > >>>> for all bridges in an encoder chain. > >>>> > >>>> Signed-off-by: Jose Abreu > >>>> Cc: Carlos Palminha > >>>> Cc: Alexey Brodkin > >>>> Cc: Ville Syrjälä > >>>> Cc: Daniel Vetter > >>>> Cc: Dave Airlie > >>>> Cc: Andrzej Hajda > >>>> Cc: Archit Taneja > >>>> --- > >>>> > >>>> drivers/gpu/drm/drm_bridge.c | 33 +++++++++++++++++++++++++++++++++ > >>>> include/drm/drm_bridge.h | 2 ++ > >>>> 2 files changed, 35 insertions(+) > >>>> > >>>> diff --git a/drivers/gpu/drm/drm_bridge.c > >>>> b/drivers/gpu/drm/drm_bridge.c > >>>> index 86a7637..dc8cdfe 100644 > >>>> --- a/drivers/gpu/drm/drm_bridge.c > >>>> +++ b/drivers/gpu/drm/drm_bridge.c > >>>> @@ -206,6 +206,39 @@ bool drm_bridge_mode_fixup(struct drm_bridge > >>>> *bridge, > >>>> > >>>> EXPORT_SYMBOL(drm_bridge_mode_fixup); > >>>> > >>>> /** > >>>> > >>>> + * drm_bridge_mode_valid - validate the mode against all bridges in > >>>> the > >>>> + * encoder chain. > >>>> + * @bridge: bridge control structure > >>>> + * @mode: desired mode to be validated > >>>> + * > >>>> + * Calls &drm_bridge_funcs.mode_valid for all the bridges in the > >>>> encoder > >>>> + * chain, starting from the first bridge to the last. If at least one > >>>> bridge + * does not accept the mode the function returns the error > >>>> code. > >>>> + * > >>>> + * Note: the bridge passed should be the one closest to the encoder. > >>>> + * > >>>> + * RETURNS: > >>>> + * MODE_OK on success, drm_mode_status Enum error code on failure > >>>> + */ > >>>> +enum drm_mode_status drm_bridge_mode_valid(struct drm_bridge *bridge, > >>>> + const struct drm_display_mode > > > > *mode) > > > >>>> +{ > >>>> + enum drm_mode_status ret = MODE_OK; > >>>> + > >>>> + if (!bridge) > >>>> + return ret; > >>>> + > >>>> + if (bridge->funcs->mode_valid) > >>>> + ret = bridge->funcs->mode_valid(bridge, mode); > >>>> + > >>>> + if (ret != MODE_OK) > >>>> + return ret; > >>>> + > >>>> + return drm_bridge_mode_valid(bridge->next, mode); > >>> > >>> Looks like it should be pretty trivial to avoid the recursion. > >>> > >>> Am I correct in interpreting this that bridges have some kind of > >>> a hand rolled linked list implementation? Reusing the standard > >>> linked lists would allow you to use list_for_each() etc. > >> > >> Yeah it's a hand-rolled list, but current hw also has a bridge nesting > >> depth of 2, so it really doesn't matter. I guess once we have real long > >> chains of bridges we can fix this (and just using list_head sounds like a > >> great idea). > > > > Even if not really needed right now, it's a pretty easy cleanup, if Jose > > has time to handle it in v3 of this series let's not postpone it ;-) > > jfyi, some of the bridge functions call the ops from the last bridge in the > chain to first, so we'd need to use list_for_each_entry_prev() (or something > like that) for them. And now that I think about it, for some of the operations (especially enable/disable) I believe that the bridge should be able to decide whether to call the next/previous bridge first or to configure its hardware first. I can image bridges that need the previous bridge in the chain to provide a valid clock before they get started, as well as bridges that need to be started with the incoming video signal stopped. -- Regards, Laurent Pinchart