From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF0214C7C for ; Mon, 16 Dec 2024 11:17:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734347825; cv=none; b=IAV9uXCfxghnurUvHyaWjVQ7rHFcMdtLmJFiJHKggw5c7y6W6mSGPOufCkdhn7I6NdCwCO/BEm6+HEFknWiB2aNt0FWS1lVQkJNFP7sPBEAQbmmIE/I6fNaLlCqgLXMKaN7bqg1z4bNC5JfYaZo5nUiYYUVLWKYdsfRGfQ6lr6g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734347825; c=relaxed/simple; bh=LoDt/I84iOmUn85JbiXoz1l5K6vlVGvplgKlEDzuhL4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aermP3XDiCb/acU1x7JoiBohq7ara61xdXx140CITYk5ZaQ3XKyvNSS3U50hSsd+935WTwFV7bXcAv/JB17PIDrmQpcuEf3zKk2zUSxwFoaduOxyJ1wyYEqE35IXMnolBF9VrnAIB8w5ZTXKQIszUHbFj9uilUh7OlzjpV+QlZM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=wmdPj+8X; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="wmdPj+8X" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id CB86413C; Mon, 16 Dec 2024 12:16:25 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1734347786; bh=LoDt/I84iOmUn85JbiXoz1l5K6vlVGvplgKlEDzuhL4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=wmdPj+8Xb0ULIoF3sPMG9ewH36j1B5HtQWrtsgpY85+YgxhXrkNV9TWyRihaUGHtF wxVe1QEJ/VMNQI6CU1MG4Z1dzq4XQhUur9h65smVvyud3NI4dN5x7QSej8ZSNBD2H7 5VfwVGdKcU5i1opWPKJlNJvMkH1j2ZasBmuo5l2Q= Date: Mon, 16 Dec 2024 13:16:45 +0200 From: Laurent Pinchart To: Sakari Ailus Cc: linux-media@vger.kernel.org, Jacopo Mondi , hverkuil@xs4all.nl Subject: Re: [PATCH v7 2/5] media: v4l: Support obtaining link frequency via get_mbus_config Message-ID: <20241216111645.GL32204@pendragon.ideasonboard.com> References: <20241210075906.609490-1-sakari.ailus@linux.intel.com> <20241210075906.609490-3-sakari.ailus@linux.intel.com> <20241215165935.GG9975@pendragon.ideasonboard.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Mon, Dec 16, 2024 at 08:46:43AM +0000, Sakari Ailus wrote: > On Sun, Dec 15, 2024 at 06:59:35PM +0200, Laurent Pinchart wrote: > > On Tue, Dec 10, 2024 at 09:59:03AM +0200, Sakari Ailus wrote: > > > Add link_freq field to struct v4l2_mbus_config in order to pass the link > > > frequency to the receiving sub-device. > > > > The documentation of v4l2_get_link_freq() should be expanded to explain > > the new mode of operation. It should document which of the supported > > methods are recommended for new drivers. > > > > > > > > Signed-off-by: Sakari Ailus > > > --- > > > drivers/media/v4l2-core/v4l2-common.c | 11 ++++++++--- > > > include/media/v4l2-mediabus.h | 2 ++ > > > 2 files changed, 10 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c > > > index 9fe74c7e064f..88fbd5608f00 100644 > > > --- a/drivers/media/v4l2-core/v4l2-common.c > > > +++ b/drivers/media/v4l2-core/v4l2-common.c > > > @@ -508,13 +508,18 @@ EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_ctrl); > > > s64 __v4l2_get_link_freq_pad(struct media_pad *pad, unsigned int mul, > > > unsigned int div) > > > { > > > + struct v4l2_mbus_config mbus_config = {}; > > > > Isn't mbus_config fully populated by the .get_mbus_config() operation ? > > That should be documented in the .get_mbus_config() operation > > documentation. > > It's a good practice to zero the memory before drivers get to work on it. I > presume drivers will set the fields that are relevant for them and ignore > the rest. > > I can add a note on get_mbus_config() the drivers should set all struct > fields to known values. Thanks. > > > struct v4l2_subdev *sd; > > > + int ret; > > > > > > sd = media_entity_to_v4l2_subdev(pad->entity); > > > - if (!sd) > > > - return -ENODEV; > > > + ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index, > > > + &mbus_config); > > > + if (ret < 0 && ret != -ENOIOCTLCMD) > > > + return ret; > > > > > > - return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div); > > > + return mbus_config.link_freq ?: > > > + __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div); > > > > if (mbus_config.link_freq) > > return mbus_config.link_freq; > > > > return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div); > > Whether this would be cleaner is debatable at least. I can switch if you > insist though. I think it's nicer. You could even write if (mbus_config.link_freq) return mbus_config.link_freq; /* * Fall back to using the link frequency control if the media bus config * doesn't provide a link frequency. */ return __v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div); > > I wonder if we should also add a message in case link_freq is 0, to get > > drivers to convert to reporting the link frequency through > > .get_mbus_config() if they already implement the operation. > > I'm not sure this will be useful: in most cases the LINK_FREQ control is > used and for a reason: it's user-configurable. Drivers should only populate > the field if the link frequency is determined by the driver. For the > receiver drivers it does not matter: they use v4l2_get_link_freq(). I think this depends on whether or not driver that have a configurable link frequency should report the current value through .get_mbus_config(). I think that drivers that implement .get_mbus_config() should, for consistency. > > > } > > > EXPORT_SYMBOL_GPL(__v4l2_get_link_freq_pad); > > > #endif /* CONFIG_MEDIA_CONTROLLER */ > > > diff --git a/include/media/v4l2-mediabus.h b/include/media/v4l2-mediabus.h > > > index 5bce6e423e94..cc5f776dc662 100644 > > > --- a/include/media/v4l2-mediabus.h > > > +++ b/include/media/v4l2-mediabus.h > > > @@ -148,6 +148,7 @@ enum v4l2_mbus_type { > > > /** > > > * struct v4l2_mbus_config - media bus configuration > > > * @type: interface type > > > + * @link_freq: The link frequency. See also V4L2_CID_LINK_FREQ control. > > > > Not a candidate for this series, but I'd like to simplify drivers by > > implementing the LINK_FREQ control automatically. > > > > > * @bus: bus configuration data structure > > > * @bus.parallel: embedded &struct v4l2_mbus_config_parallel. > > > * Used if the bus is parallel or BT.656. > > > @@ -162,6 +163,7 @@ enum v4l2_mbus_type { > > > */ > > > struct v4l2_mbus_config { > > > enum v4l2_mbus_type type; > > > + u64 link_freq; > > > union { > > > struct v4l2_mbus_config_parallel parallel; > > > struct v4l2_mbus_config_mipi_csi1 mipi_csi1; -- Regards, Laurent Pinchart