Re: [PATCH v5 02/24] drm: Add drm_connector_init() variant with ddc

From: Jani Nikula <jani.nikula@linux.intel.com>
To: Andrzej Pietrasiewicz <andrzej.p@collabora.com>,
	dri-devel@lists.freedesktop.org
Cc: "Y.C. Chen" <yc_chen@aspeedtech.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Sam Ravnborg" <sam@ravnborg.org>,
	"Neil Armstrong" <narmstrong@baylibre.com>,
	"David Airlie" <airlied@linux.ie>,
	"Douglas Anderson" <dianders@chromium.org>,
	"Andrzej Hajda" <a.hajda@samsung.com>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Benjamin Gaignard" <benjamin.gaignard@linaro.org>,
	kernel@collabora.com, "Fabio Estevam" <festevam@gmail.com>,
	"David (ChunMing) Zhou" <David1.Zhou@amd.com>,
	linux-samsung-soc@vger.kernel.org,
	"Joonyoung Shim" <jy0922.shim@samsung.com>,
	linux-rockchip@lists.infradead.org,
	"Vincent Abriou" <vincent.abriou@st.com>,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Jonathan Hunter" <jonathanh@nvidia.com>,
	"Maxime Ripard" <maxime.ripard@bootlin.com>,
	"Chen-Yu Tsai" <wens@csie.org>, "Kukjin Kim" <kgene@kernel.org>,
	"NXP Linux Team" <linux-imx@nxp.com>, "CK Hu" <ck.hu@mediatek.co>
Subject: Re: [PATCH v5 02/24] drm: Add drm_connector_init() variant with ddc
Date: Mon, 29 Jul 2019 11:42:43 +0300	[thread overview]
Message-ID: <875znlp6yk.fsf@intel.com> (raw)
In-Reply-To: <53f5ded2971235e5b63c9a3ed4ed8bccf10c78f2.1563960855.git.andrzej.p@collabora.com>

On Wed, 24 Jul 2019, Andrzej Pietrasiewicz <andrzej.p@collabora.com> wrote:
> Allow passing ddc adapter pointer to the init function. Even if
> drm_connector_init() sometime in the future decides to e.g. memset() all
> connector fields to zeros, the newly added function ensures that at its
> completion the ddc member of connector is correctly set.
>
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 19 +++++++++++++++++++
>  include/drm/drm_connector.h     |  5 +++++
>  2 files changed, 24 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 068d4b05f1be..06fbfc44fb48 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -296,6 +296,25 @@ int drm_connector_init(struct drm_device *dev,
>  }
>  EXPORT_SYMBOL(drm_connector_init);
>  
> +int drm_connector_init_with_ddc(struct drm_device *dev,
> +				struct drm_connector *connector,
> +				const struct drm_connector_funcs *funcs,
> +				int connector_type,
> +				struct i2c_adapter *ddc)

Playing the devil's advocate here a bit. What if you end up adding
another thing you need to initialize like this? Are you going to need
three more functions to account for the combinations? Init with ddc,
with foo, with ddc and foo? So I generally frown upon interfaces like
this.

If everyone thinks this is the way to go, I'm not going to stand in the
way, but personally I'd rather switch over all of i915 to a new version
of drm_connector_init() that just takes another parameter.

BR,
Jani.

> +{
> +	int ret;
> +
> +	ret = drm_connector_init(dev, connector, funcs, connector_type);
> +	if (ret)
> +		return ret;
> +
> +	/* provide ddc symlink in sysfs */
> +	connector->ddc = ddc;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_connector_init_with_ddc);
> +
>  /**
>   * drm_connector_attach_edid_property - attach edid property.
>   * @connector: the connector
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 33a6fff85fdb..937fda9c1374 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1410,6 +1410,11 @@ int drm_connector_init(struct drm_device *dev,
>  		       struct drm_connector *connector,
>  		       const struct drm_connector_funcs *funcs,
>  		       int connector_type);
> +int drm_connector_init_with_ddc(struct drm_device *dev,
> +				struct drm_connector *connector,
> +				const struct drm_connector_funcs *funcs,
> +				int connector_type,
> +				struct i2c_adapter *ddc);
>  void drm_connector_attach_edid_property(struct drm_connector *connector);
>  int drm_connector_register(struct drm_connector *connector);
>  void drm_connector_unregister(struct drm_connector *connector);

-- 
Jani Nikula, Intel Open Source Graphics Center
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