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[23.128.96.18]) by mx.google.com with ESMTP id y13si10741237edo.465.2021.06.14.00.35.31; Mon, 14 Jun 2021 00:35:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232541AbhFNHfn (ORCPT + 99 others); Mon, 14 Jun 2021 03:35:43 -0400 Received: from relay8-d.mail.gandi.net ([217.70.183.201]:59627 "EHLO relay8-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232424AbhFNHfm (ORCPT ); Mon, 14 Jun 2021 03:35:42 -0400 Received: (Authenticated sender: jacopo@jmondi.org) by relay8-d.mail.gandi.net (Postfix) with ESMTPSA id 116541BF20D; Mon, 14 Jun 2021 07:33:34 +0000 (UTC) Date: Mon, 14 Jun 2021 09:34:25 +0200 From: Jacopo Mondi To: Jacopo Mondi , Mauro Carvalho Chehab , Sakari Ailus , Hans Verkuil Cc: kieran.bingham+renesas@ideasonboard.com, laurent.pinchart+renesas@ideasonboard.com, niklas.soderlund+renesas@ragnatech.se, geert@linux-m68k.org, linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 16/17] media: v4l2-subdev: De-deprecate init() subdev op Message-ID: <20210614073425.p4dlkx5tv5pddogo@uno.localdomain> References: <20210412093451.14198-1-jacopo+renesas@jmondi.org> <20210412093451.14198-17-jacopo+renesas@jmondi.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210412093451.14198-17-jacopo+renesas@jmondi.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello linux-media, On Mon, Apr 12, 2021 at 11:34:50AM +0200, Jacopo Mondi wrote: > The init() subdev core operation is deemed to be deprecated for new > subdevice drivers. However it could prove useful for complex > architectures to defer operation that require access to the > communication bus if said bus is not available (or fully configured) > at the time when the subdevice probe() function is run. > > As an example, the GMSL architecture requires the GMSL configuration > link to be configured on the host side after the remote subdevice > has completed its probe function. After the configuration on the host > side has been performed, the subdevice registers can be accessed through > the communication bus. > > In particular: > > HOST REMOTE > > probe() > | > ---------------------> | > probe() { > bus config() > } > |<--------------------| > v4l2 async bound { > bus config() > call subdev init() > |-------------------->| > init() { > access register on the bus() > } > |<------------------- > } > > In the GMSL use case the bus configuration requires the enablement of the > noise immunity threshold on the remote side which ensures reliability > of communications in electrically noisy environments. After the subdevice > has enabled the threshold at the end of its probe() sequence the host > side shall compensate it with an higher signal amplitude. Once this > sequence has completed the bus can be accessed with noise protection > enabled and all the operations that require a considerable number of > transactions on the bus (such as the image sensor configuration > sequence) are run in the subdevice init() operation implementation. > > Signed-off-by: Jacopo Mondi This change is key for the whole series to get in, and requires the approval of linux-media maintainers as it use a function now deemed as deprecated. Could I get an ack/nack please ? Thanks j > --- > include/media/v4l2-subdev.h | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h > index d0e9a5bdb08b..3068d9940669 100644 > --- a/include/media/v4l2-subdev.h > +++ b/include/media/v4l2-subdev.h > @@ -148,9 +148,18 @@ struct v4l2_subdev_io_pin_config { > * each pin being configured. This function could be called at times > * other than just subdevice initialization. > * > - * @init: initialize the sensor registers to some sort of reasonable default > - * values. Do not use for new drivers and should be removed in existing > - * drivers. > + * @init: initialize the subdevice registers to some sort of reasonable default > + * values. Do not use for new drivers (and should be removed in existing > + * ones) for regular architectures where the image sensor is connected to > + * the host receiver. For more complex architectures where the subdevice > + * initialization should be deferred to the completion of the probe > + * sequence of some intermediate component, or the communication bus > + * requires configurations on the host side that depend on the completion > + * of the probe sequence of the remote subdevices, the usage of this > + * operation could be considered to allow the devices along the pipeline to > + * probe and register in the media graph and to defer any operation that > + * require actual access to the communication bus to their init() function > + * implementation. > * > * @load_fw: load firmware. > * > -- > 2.31.1 >