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 5DF20C4167B for ; Thu, 15 Dec 2022 12:49:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229870AbiLOMta (ORCPT ); Thu, 15 Dec 2022 07:49:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229543AbiLOMtI (ORCPT ); Thu, 15 Dec 2022 07:49:08 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 020F9221 for ; Thu, 15 Dec 2022 04:49:03 -0800 (PST) Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 02B4CFB; Thu, 15 Dec 2022 13:49:01 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1671108542; bh=mp61nf2ScvV944VCCIpe9cw4//xtj6rw0Et154PjP/s=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pRm33B87oKFUmCWKZFrzBrXDjaCK/G8KQH42GxodivctrSdo4VSbGQmOJaOF6055c woUBzTHKuxUYKCxpvrzGyl5ZUctprL7Qz3TKH9xQ3vDMEzaJAIp/eCp4s963PkFvTy 0MHxx6KS0Q3igYWHMueT4eu63PS9N71oEypLZLjY= Date: Thu, 15 Dec 2022 14:48:58 +0200 From: Laurent Pinchart To: Tomi Valkeinen Cc: linux-media@vger.kernel.org, Sakari Ailus , Michal Simek , Sylwester Nawrocki Subject: Re: [PATCH v1 1/5] media: mc: entity: Add pad iterator for media_pipeline Message-ID: References: <20221212141621.724-1-laurent.pinchart@ideasonboard.com> <20221212141621.724-2-laurent.pinchart@ideasonboard.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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. > > /** > > * 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. > > + * Iterate on all pads in a media pipeline. This is only valid after the > > + * pipeline has been built with media_pipeline_start() and before it gets > > + * destroyed with media_pipeline_stop(). > > + */ > > +#define media_pipeline_for_each_pad(pipe, iter, pad) \ > > + for (pad = __media_pipeline_pad_iter_next((pipe), iter, NULL); \ > > + pad != NULL; \ > > + pad = __media_pipeline_pad_iter_next((pipe), iter, pad)) > > + > > /** > > * media_pipeline_alloc_start - Mark a pipeline as streaming > > * @pad: Starting pad -- Regards, Laurent Pinchart