From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from perceval.ideasonboard.com ([95.142.166.194]:53565 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932940Ab2KNK5s (ORCPT ); Wed, 14 Nov 2012 05:57:48 -0500 From: Laurent Pinchart To: Sylwester Nawrocki Cc: Sakari Ailus , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, alsa-devel@alsa-project.org, broonie@opensource.wolfsonmicro.com, hverkuil@xs4all.nl Subject: Re: [PATCH 1/1] media: Entities with sink pads must have at least one enabled link Date: Wed, 14 Nov 2012 11:58:42 +0100 Message-ID: <2181130.3OlxHxCofA@avalon> In-Reply-To: <50A36307.50502@samsung.com> References: <1351280777-4936-1-git-send-email-sakari.ailus@iki.fi> <20121113142409.GR25623@valkosipuli.retiisi.org.uk> <50A36307.50502@samsung.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-media-owner@vger.kernel.org List-ID: Hi Sylwester, On Wednesday 14 November 2012 10:23:19 Sylwester Nawrocki wrote: > On 11/13/2012 03:24 PM, Sakari Ailus wrote: > > Hi all, > > > > Comments would be appreciated, either positive or negative. The omap3isp > > driver does the same check itself currently, but I think this is more > > generic than that. > > > > Thanks. > > > > On Fri, Oct 26, 2012 at 10:46:17PM +0300, Sakari Ailus wrote: > >> If an entity has sink pads, at least one of them must be connected to > >> another pad with an enabled link. If a driver with multiple sink pads has > >> more strict requirements the check should be done in the driver itself. > >> > >> Just requiring one sink pad is connected with an enabled link is enough > >> API-wise: entities with sink pads with only disabled links should not be > >> allowed to stream in the first place, but also in a different operation > >> mode a device might require only one of its pads connected with an > >> active link. > >> > >> If an entity has an ability to function as a source entity another > >> logical entity connected to the aforementioned one should be used for the > >> purpose. > > Why not leave it to individual drivers ? I'm not sure if it is a good idea > not to allow an entity with sink pads to be used as a source only. It might > be appropriate for most of the cases but likely not all. I'm inclined not to > add this requirement in the API. Just my opinion though. I have mixed feelings about this patch too, which is why I've asked Sakari to cross-post it. It's pretty easy to add this check to the core now, but pushing it back to drivers late if we realize it's too restrictive would be difficult. I think my preference would go for a helper function that drivers can use, possibly first waiting until a second driver requires this kind of checks before implementing it. -- Regards, Laurent Pinchart