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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 AAAA3C4BA24 for ; Wed, 26 Feb 2020 20:39:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 84A0B24672 for ; Wed, 26 Feb 2020 20:39:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727460AbgBZUjz (ORCPT ); Wed, 26 Feb 2020 15:39:55 -0500 Received: from retiisi.org.uk ([95.216.213.190]:49582 "EHLO hillosipuli.retiisi.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727379AbgBZUjz (ORCPT ); Wed, 26 Feb 2020 15:39:55 -0500 Received: from valkosipuli.localdomain (valkosipuli.retiisi.org.uk [IPv6:2a01:4f9:c010:4572::80:2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by hillosipuli.retiisi.org.uk (Postfix) with ESMTPS id E5882634C87; Wed, 26 Feb 2020 22:38:39 +0200 (EET) Received: from sailus by valkosipuli.localdomain with local (Exim 4.92) (envelope-from ) id 1j73S4-0002Lc-II; Wed, 26 Feb 2020 22:38:40 +0200 Date: Wed, 26 Feb 2020 22:38:40 +0200 From: Sakari Ailus To: Ezequiel Garcia Cc: linux-media@vger.kernel.org, Hans Verkuil , kernel@collabora.com, Laurent Pinchart , Steve Longerbeam , Philipp Zabel , Maxime Ripard Subject: Re: [PATCH v2] media: Split v4l2_pipeline_pm_use into v4l2_pipeline_pm_{get, put} Message-ID: <20200226203840.GP5023@valkosipuli.retiisi.org.uk> References: <20200124203543.22890-1-ezequiel@collabora.com> <20200226155336.GO5023@valkosipuli.retiisi.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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. -- Kind regards, Sakari Ailus