From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4306CC43219 for ; Thu, 25 Apr 2019 17:59:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9242206BF for ; Thu, 25 Apr 2019 17:59:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="pgzroVIN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730059AbfDYR73 (ORCPT ); Thu, 25 Apr 2019 13:59:29 -0400 Received: from perceval.ideasonboard.com ([213.167.242.64]:38406 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726199AbfDYR73 (ORCPT ); Thu, 25 Apr 2019 13:59:29 -0400 Received: from pendragon.ideasonboard.com (net-37-182-44-227.cust.vodafonedsl.it [37.182.44.227]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 081ED5F; Thu, 25 Apr 2019 19:59:25 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1556215166; bh=hMFo5LJYIOc8aE3CjuyJzgdqYSZukamjRh8Gh+GQLTs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pgzroVINvUiav+qSFs90cB9UWPLN0i0yHXrfq45IUZkgFXdOIJ1fktOj7Ex1NvLrR sWHszVmyxVFl9D7kkoO2fOgmfa7yMp1ckg6lbfahKs8zpHvIVV0MmDSOjuY0SRyO+z ZixZc1lAwaeVJbPLi45MSaPJliN00KSPMZlEoRio= Date: Thu, 25 Apr 2019 20:59:15 +0300 From: Laurent Pinchart To: Matt Redfearn Cc: Andrzej Hajda , Philippe Cornu , "dri-devel@lists.freedesktop.org" , Matthew Redfearn , Nickey Yang , Heiko Stuebner , Archit Taneja , "linux-kernel@vger.kernel.org" , David Airlie , Daniel Vetter Subject: Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable Message-ID: <20190425175915.GB12024@pendragon.ideasonboard.com> References: <20190424142148.25927-1-matt.redfearn@thinci.com> <3da4c0a3-a77b-5128-63f7-9c8d6b012c68@samsung.com> <95c36782-7eaf-2224-bb52-cff0a53d98d8@thinci.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <95c36782-7eaf-2224-bb52-cff0a53d98d8@thinci.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Matt, On Thu, Apr 25, 2019 at 12:39:27PM +0000, Matt Redfearn wrote: > On 25/04/2019 13:13, Andrzej Hajda wrote: > > On 24.04.2019 16:22, Matt Redfearn wrote: > >> The DRM documentation states that post_disable is an optional callback. > >> As such an implementing device may not populate it. To avoid panicing > >> the kernel by calling a NULL function pointer, we should NULL check it > >> before blindy calling it. > >> > >> Signed-off-by: Matt Redfearn > > > >> --- > >> > >> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c > >> index 38e88071363..0ee440216b8 100644 > >> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c > >> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c > >> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct drm_bridge *bridge) > >> * This needs to be fixed in the drm_bridge framework and the API > >> * needs to be updated to manage our own call chains... > >> */ > >> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge); > >> + if (dsi->panel_bridge->funcs->post_disable) > >> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge); > >> > > > > Why not drm_bridge_post_disable ? > > Ah - that seems like a nicer fix! Do you think the comment above > describing why this function pointer is called directly can be removed > as well if we go this route? It shouldn't be necessary to call ->post_disable manually here as the bridge core handles it internally. This is a hack to work around a problem, and should be fixed properly. > If someone calls drm_bridge_post_disable() on the Synposys DSI > drm_bridge it will go on to call post_disable on all other bridges in > the chain, in addition to us calling them here. Is it an issue to call > it multiple times? It depends on the panel implementation, but in general it's not a good idea. It may happen to work, but could break at any time in the future. > >> if (dsi->slave) { > >> dw_mipi_dsi_disable(dsi->slave); -- Regards, Laurent Pinchart