Re: [PATCH] drm/sun4i: hdmi: add support for ddc-i2c-bus property

Måns Rullgård
2019-03-11T16:11:09Z

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.

--
Måns Rullgård