From: Maxime Ripard <maxime.ripard@bootlin.com>
To: "Måns Rullgård" <mans@mansr.com>
Cc: David Airlie <airlied@linux.ie>, Chen-Yu Tsai <wens@csie.org>,
dri-devel@lists.freedesktop.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/sun4i: hdmi: add support for ddc-i2c-bus property
Date: Thu, 14 Mar 2019 16:41:05 +0100 [thread overview]
Message-ID: <20190314154105.o6r7hzeuiyajxh7v@flea> (raw)
In-Reply-To: <yw1xef7d4cit.fsf@mansr.com>
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On Mon, Mar 11, 2019 at 04:11:06PM +0000, Måns Rullgård wrote:
> Maxime Ripard <maxime.ripard@bootlin.com> writes:
>
> > Hi!
> >
> > On Mon, Mar 11, 2019 at 01:47:13PM +0000, Mans Rullgard wrote:
> >> Sometimes it is desirabled to use a separate i2c controller for ddc
> >> access. This adds support for the ddc-i2c-bus property of the
> >> hdmi-connector node, using the specified controller if provided.
> >>
> >> Signed-off-by: Mans Rullgard <mans@mansr.com>
> >> ---
> >> drivers/gpu/drm/sun4i/sun4i_hdmi.h | 1 +
> >> drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 37 +++++++++++++++++++++++---
> >> 2 files changed, 35 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi.h b/drivers/gpu/drm/sun4i/sun4i_hdmi.h
> >> index b685ee11623d..b08c4453d47c 100644
> >> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi.h
> >> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi.h
> >> @@ -269,6 +269,7 @@ struct sun4i_hdmi {
> >> struct clk *tmds_clk;
> >>
> >> struct i2c_adapter *i2c;
> >> + struct i2c_adapter *ddc_i2c;
> >>
> >> /* Regmap fields for I2C adapter */
> >> struct regmap_field *field_ddc_en;
> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> >> index 061d2e0d9011..5b2fac79f5d6 100644
> >> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> >> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
> >> @@ -212,7 +212,7 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector)
> >> struct edid *edid;
> >> int ret;
> >>
> >> - edid = drm_get_edid(connector, hdmi->i2c);
> >> + edid = drm_get_edid(connector, hdmi->ddc_i2c ?: hdmi->i2c);
> >
> > You can't test whether ddc_i2c is NULL or not...
> >
> >> if (!edid)
> >> return 0;
> >>
> >> @@ -228,6 +228,28 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector)
> >> return ret;
> >> }
> >>
> >> +static struct i2c_adapter *sun4i_hdmi_get_ddc(struct device *dev)
> >> +{
> >> + struct device_node *phandle, *remote;
> >> + struct i2c_adapter *ddc;
> >> +
> >> + remote = of_graph_get_remote_node(dev->of_node, 1, -1);
> >> + if (!remote)
> >> + return ERR_PTR(-EINVAL);
> >> +
> >> + phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
> >> + of_node_put(remote);
> >> + if (!phandle)
> >> + return NULL;
> >> +
> >> + ddc = of_get_i2c_adapter_by_node(phandle);
> >> + of_node_put(phandle);
> >> + if (!ddc)
> >> + return ERR_PTR(-EPROBE_DEFER);
> >> +
> >> + return ddc;
> >
> > ... Since even in (most) error cases you're returning a !NULL pointer.
> >
> >> +}
> >> +
> >> static const struct drm_connector_helper_funcs sun4i_hdmi_connector_helper_funcs = {
> >> .get_modes = sun4i_hdmi_get_modes,
> >> };
> >> @@ -575,6 +597,12 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
> >> goto err_disable_mod_clk;
> >> }
> >>
> >> + hdmi->ddc_i2c = sun4i_hdmi_get_ddc(dev);
> >> + if (IS_ERR(hdmi->ddc_i2c)) {
>
> ... which is checked here.
>
> The property is optional, so the idea was to return null in that case
> and use the built-in controller. If the property exists but some error
> occurs, we want to abort rather than proceed with the fallback which
> almost certainly won't work.
>
> Maybe I got something wrong in that logic.
Indeed, I just got confused. I guess returning ENODEV in such a case,
and testing for that, would make things more obvious.
Thanks!
Maxime
--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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next prev parent reply other threads:[~2019-03-14 15:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-11 13:47 [PATCH] drm/sun4i: hdmi: add support for ddc-i2c-bus property Mans Rullgard
2019-03-11 15:47 ` Maxime Ripard
2019-03-11 16:11 ` Måns Rullgård
2019-03-14 15:41 ` Maxime Ripard [this message]
2019-03-14 16:09 ` Måns Rullgård
2019-03-18 15:50 ` Maxime Ripard
2019-03-18 16:23 ` Måns Rullgård
2019-03-19 12:34 ` Maxime Ripard
2019-03-19 12:48 ` Måns Rullgård
2019-03-21 15:44 ` Maxime Ripard
2019-03-21 18:00 ` Måns Rullgård
2019-03-26 19:49 ` Maxime Ripard
2019-03-28 13:02 ` Mans Rullgard
2019-04-01 11:58 ` Maxime Ripard
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