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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58C87C4332F for ; Thu, 15 Dec 2022 12:55:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229558AbiLOMzf (ORCPT ); Thu, 15 Dec 2022 07:55:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229506AbiLOMze (ORCPT ); Thu, 15 Dec 2022 07:55:34 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 681B22AE31 for ; Thu, 15 Dec 2022 04:55:32 -0800 (PST) Received: from [192.168.1.15] (91-154-32-225.elisa-laajakaista.fi [91.154.32.225]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id B5AF3FB; Thu, 15 Dec 2022 13:55:30 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1671108931; bh=wrQRxylTQHwduWKubzS0Ev1x+RazL4sOM2FbGxYWWvo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=WbywI+NuPxqOgTxLTyshMd3RnyLqgN+ATOo8By7zx1jlrseopLELfCSMR/LgsMLb0 58WKNyvD9EkfJNQ7WsbnChk8GNDIG4ZFgIfvwQqsbkRbUKkHw61j8/TQdgpOAYNBLG q0zmyE9Rwr/1U379vbeweRFkPOFVO3sd3Pe4aJCE= Message-ID: <528db496-45ea-e695-16a1-0d332b9f3997@ideasonboard.com> Date: Thu, 15 Dec 2022 14:55:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH v1 1/5] media: mc: entity: Add pad iterator for media_pipeline Content-Language: en-US To: Laurent Pinchart Cc: linux-media@vger.kernel.org, Sakari Ailus , Michal Simek , Sylwester Nawrocki References: <20221212141621.724-1-laurent.pinchart@ideasonboard.com> <20221212141621.724-2-laurent.pinchart@ideasonboard.com> From: Tomi Valkeinen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 15/12/2022 14:48, Laurent Pinchart wrote: > Hi Tomi, > > On Thu, Dec 15, 2022 at 02:33:43PM +0200, Tomi Valkeinen wrote: >> On 12/12/2022 16:16, Laurent Pinchart wrote: >>> Add a media_pipeline_for_each_pad() macro to iterate over pads in a >>> pipeline. This should be used by driver as a replacement of the >>> media_graph_walk API, as iterating over the media_pipeline uses the >>> cached list of pads and is thus more efficient. >>> >>> Signed-off-by: Laurent Pinchart >>> --- >>> drivers/media/mc/mc-entity.c | 18 ++++++++++++++++++ >>> include/media/media-entity.h | 29 +++++++++++++++++++++++++++++ >>> 2 files changed, 47 insertions(+) >>> >>> diff --git a/drivers/media/mc/mc-entity.c b/drivers/media/mc/mc-entity.c >>> index b8bcbc734eaf..70df2050951c 100644 >>> --- a/drivers/media/mc/mc-entity.c >>> +++ b/drivers/media/mc/mc-entity.c >>> @@ -932,6 +932,24 @@ __must_check int media_pipeline_alloc_start(struct media_pad *pad) >>> } >>> EXPORT_SYMBOL_GPL(media_pipeline_alloc_start); >>> >>> +struct media_pad * >>> +__media_pipeline_pad_iter_next(struct media_pipeline *pipe, >>> + struct media_pipeline_pad_iter *iter, >>> + struct media_pad *pad) >>> +{ >>> + if (!pad) >>> + iter->cursor = pipe->pads.next; >>> + >>> + if (iter->cursor == &pipe->pads) >>> + return NULL; >>> + >>> + pad = list_entry(iter->cursor, struct media_pipeline_pad, list)->pad; >>> + iter->cursor = iter->cursor->next; >>> + >>> + return pad; >>> +} >>> +EXPORT_SYMBOL_GPL(__media_pipeline_pad_iter_next); >>> + >>> /* ----------------------------------------------------------------------------- >>> * Links management >>> */ >>> diff --git a/include/media/media-entity.h b/include/media/media-entity.h >>> index 85ed08ddee9d..e881e483b550 100644 >>> --- a/include/media/media-entity.h >>> +++ b/include/media/media-entity.h >>> @@ -130,6 +130,15 @@ struct media_pipeline_pad { >>> struct media_pad *pad; >>> }; >>> >>> +/** >>> + * struct media_pipeline_pad_iter - Iterator for media_pipeline_for_each_pad >>> + * >>> + * @cursor: The current element >>> + */ >>> +struct media_pipeline_pad_iter { >>> + struct list_head *cursor; >>> +}; >>> + >> >> Is there any reason to have this iter struct in a public header, vs. >> having it in mc-entity.c? > > It has to be instantiated on the stack by the user of the > media_pipeline_for_each_pad() macro. A typical usage is > > struct media_pipeline_pad_iter iter; > struct media_pad *pad > > media_pipeline_for_each_pad(pipe, &iter, pad) { > ... > }; > > Note how iter is not a pointer. Ah, right. >>> /** >>> * struct media_link - A link object part of a media graph. >>> * >>> @@ -1163,6 +1172,26 @@ void media_pipeline_stop(struct media_pad *pad); >>> */ >>> void __media_pipeline_stop(struct media_pad *pad); >>> >>> +struct media_pad * >>> +__media_pipeline_pad_iter_next(struct media_pipeline *pipe, >>> + struct media_pipeline_pad_iter *iter, >>> + struct media_pad *pad); >>> + >>> +/** >>> + * media_pipeline_for_each_pad - Iterate on all pads in a media pipeline >>> + * @pipe: The pipeline >>> + * @iter: The iterator (struct media_pipeline_pad_iter) >>> + * @pad: The iterator pad >> >> If I understand this correctly, both iter and pad are just variables the >> macro will use. In other words, they are not used to pass any values. >> >> Would it be better to declare those variables in the macro itself? Well, >> that has its downsides. But perhaps at least clarify in the doc that >> they are only variables used by the loop, and do not need to be initialized. > > Now that the kernel uses C99, I suppose we could make the pad variable > locally declared within the loop: > > #define media_pipeline_for_each_pad(pipe, pad) \ > for (struct media_pipeline_pad *pad = __media_pipeline_pad_iter_next((pipe), iter, NULL); \ > pad != NULL; \ > pad = __media_pipeline_pad_iter_next((pipe), iter, pad)) > > Hiding the iter variable would be more difficult, as I don't think you > can declare multiple variables of different types. > > I'm a bit concerned about backporting though, so I'd rather not do this > in this patch, but on top. I was thinking about using a do {} while(0) around the for loop to declare the variables, but.. of course that can't be used here. One shouldn't do reviews when one has a cold =). Tomi