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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=no 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 D45A8C4BA24 for ; Wed, 26 Feb 2020 21:08:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB0EA2072D for ; Wed, 26 Feb 2020 21:08:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727485AbgBZVIt (ORCPT ); Wed, 26 Feb 2020 16:08:49 -0500 Received: from bhuna.collabora.co.uk ([46.235.227.227]:57280 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727444AbgBZVIt (ORCPT ); Wed, 26 Feb 2020 16:08:49 -0500 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: ezequiel) with ESMTPSA id 57C69293984 Message-ID: <073fdfdf8dadf2d33a049c5c6a87fca1a78c4fad.camel@collabora.com> Subject: Re: [PATCH v2] media: Split v4l2_pipeline_pm_use into v4l2_pipeline_pm_{get, put} From: Ezequiel Garcia To: Sakari Ailus Cc: linux-media@vger.kernel.org, Hans Verkuil , kernel@collabora.com, Laurent Pinchart , Steve Longerbeam , Philipp Zabel , Maxime Ripard Date: Wed, 26 Feb 2020 18:08:40 -0300 In-Reply-To: <20200226203840.GP5023@valkosipuli.retiisi.org.uk> References: <20200124203543.22890-1-ezequiel@collabora.com> <20200226155336.GO5023@valkosipuli.retiisi.org.uk> <20200226203840.GP5023@valkosipuli.retiisi.org.uk> Organization: Collabora Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.1-2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On Wed, 2020-02-26 at 22:38 +0200, Sakari Ailus wrote: > Hi Ezequiel, > > On Wed, Feb 26, 2020 at 02:28:08PM -0300, Ezequiel Garcia wrote: > > Hello Sakari, > > > > Thanks a lot for your comments. > > > > On Wed, 2020-02-26 at 17:53 +0200, Sakari Ailus wrote: > > > Hi Ezequiel, > > > > > > On Fri, Jan 24, 2020 at 05:35:43PM -0300, Ezequiel Garcia wrote: > > > > Currently, v4l2_pipeline_pm_use() prototype is: > > > > > > > > int v4l2_pipeline_pm_use(struct media_entity *entity, int use) > > > > > > > > Where the 'use' argument shall only be set to '1' for enable/power-on, > > > > or to '0' for disable/power-off. The integer return is specified > > > > as only meaningful when 'use' is set to '1'. > > > > > > > > Let's enforce this semantic by splitting the function in two: > > > > v4l2_pipeline_pm_get and v4l2_pipeline_pm_put. This is done > > > > for several reasons. > > > > > > > > It makes the API easier to use (or harder to misuse). > > > > It removes the constraint on the values the 'use' argument > > > > shall take. Also, it removes the need to constraint > > > > the return value, by making v4l2_pipeline_pm_put void return. > > > > > > > > And last, it's more consistent with other kernel APIs, such > > > > as the runtime pm APIs, which makes the code more symmetric. > > > > > > Indeed. These functions only exist because not all sensor etc. drivers have > > > been converted to runtime PM yet. New drivers no longer implement s_power > > > callbacks. > > > > > > I don't object the patch as such, but I think you could also add a note > > > that relying on the s_power callback is deprecated. This probably should be > > > a separate patch. > > > > > > > Hans picked this patch, sending a pull request yesterday which includes it. > > > > Since you know this API better than me, I thikn it would be best > > if you take care of sending a patch for it. > > > > In particular, I'd like to know as reference, if any changes are needed > > RKISP1 and sensors such as IMX219 in order to avoid relying in the deprecated > > API. > > I do look for the s_power callback when reviewing the driver. :-) > > ISP drivers may, I think, omit calling s_power if they don't need to work > with sensor drivers that require it. In that case, one could as well fix > the sensor driver. > > > Moreover, is there any way we can add some build time or run time warning, > > to avoid developers from using an API that is deprecated? > > Getting rid of s_power is a long project, so a warning every time it's used > would be quite a nuisance. I think documentation is the way to go. > > I can send a patch. > Hey Sakari, I know everyone should always read headers, comments and documentation, but since reality might be different how about: diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c index a376b351135f..eca341c3cb17 100644 --- a/drivers/media/v4l2-core/v4l2-subdev.c +++ b/drivers/media/v4l2-core/v4l2-subdev.c @@ -802,6 +802,8 @@ void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops) { INIT_LIST_HEAD(&sd->list); BUG_ON(!ops); + if (ops->core && ops->core->s_power) + pr_warn_once("Warning: s_power is deprecated. Please use foo and bar instead\n"); sd->ops = ops; sd->v4l2_dev = NULL; sd->flags = 0; Do you think that's too noisy? Cheers, Ezequiel