On Mon, Mar 18, 2019 at 04:23:56PM +0000, Måns Rullgård wrote:
Maxime Ripard maxime.ripard@bootlin.com writes:
On Thu, Mar 14, 2019 at 04:09:13PM +0000, Måns Rullgård wrote:
Maxime Ripard maxime.ripard@bootlin.com writes:
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.
There's also a case I hadn't thought of: property exists but isn't a valid phandle. What do you think is the correct action in that case?
I think we would have that one covered. of_parse_phandle will return !NULL, but then of_get_i2c_adapter_by_node will return NULL since we wouldn't have an associated i2c adapter to the bogus phandle, and you are checking for that already.
of_parse_phandle() doesn't differentiate between a missing property and an existing non-phandle value. The following cases are possible with this patch:
- ddc-i2c-bus points to valid i2c controller node: use this for ddc
- no ddc-i2c-bus property: return NULL, use internal i2c
- ddc-i2c-bus exists but isn't a phandle: likewise
- ddc-i2c-bus points to a non-i2c-controller node: EPROBE_DEFER
The last two cases obviously mean the devicetree is invalid, so perhaps it doesn't matter much what happens then. I don't think it's possible to distinguish between a well-formed phandle pointing to some bogus node and a good one where the i2c driver hasn't been probed yet.
Ah, I see what you mean now. Yeah, there's not much we can do against a wrong / corrupted DT. The DT validation would help prevent the third case, and possibly the fourth, but that's basically the only thing we can do.
Maxime
-- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com