| Message ID | 20160720095857.12297-5-maxime.ripard@free-electrons.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jul 20, 2016 at 11:58:54AM +0200, Maxime Ripard wrote: > Some boards have an entirely passive RGB to VGA bridge, based on either > DACs or resistor ladders. > > Those might or might not have an i2c bus routed to the VGA connector in > order to access the screen EDIDs. > > Add a bridge that doesn't do anything but expose the modes available on the > screen, either based on the EDIDs if available, or based on the XGA > standards. > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> > --- > .../bindings/display/bridge/dumb-vga.txt | 54 +++++ > drivers/gpu/drm/bridge/Kconfig | 6 + > drivers/gpu/drm/bridge/Makefile | 1 + > drivers/gpu/drm/bridge/dumb-vga.c | 232 +++++++++++++++++++++ > 4 files changed, 293 insertions(+) > create mode 100644 Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > create mode 100644 drivers/gpu/drm/bridge/dumb-vga.c > > diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > new file mode 100644 > index 000000000000..0056ffa2b31d > --- /dev/null > +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > @@ -0,0 +1,54 @@ > +Passive RGB to VGA bridge > +------------------------- > + > +This binding is aimed for entirely passive RGB to VGA bridges that do not > +require any configuration. > + > +Required properties: > + > +- compatible: Must be "dumb-vga-bridge" > + > +Required nodes: > + > +This device has two video ports. Their connections are modeled using the OF > +graph bindings specified in Documentation/devicetree/bindings/graph.txt. > + > +- Video port 0 for RGB input > +- Video port 1 for VGA output > + > + > +Example > +------- > + > +bridge { > + compatible = "dumb-vga-bridge"; > + #address-cells = <1>; > + #size-cells = <0>; > + > + ports { > + #address-cells = <1>; > + #size-cells = <0>; > + > + port@0 { > + #address-cells = <1>; > + #size-cells = <0>; > + reg = <0>; > + > + vga_bridge_in: endpoint@0 { > + reg = <0>; Don't need a unit address here. > + remote-endpoint = <&tcon0_out_vga>; > + }; > + }; > + > + port@1 { > + #address-cells = <1>; > + #size-cells = <0>; > + reg = <1>; > + > + vga_bridge_out: endpoint@0 { > + reg = <0>; Ditto. > + remote-endpoint = <&vga_con_in>; Would be good to show the connector node in the example too. With those changes, Acked-by: Rob Herring <robh@kernel.org>
Hi, On 07/20/2016 03:28 PM, Maxime Ripard wrote: > Some boards have an entirely passive RGB to VGA bridge, based on either > DACs or resistor ladders. > > Those might or might not have an i2c bus routed to the VGA connector in > order to access the screen EDIDs. > > Add a bridge that doesn't do anything but expose the modes available on the > screen, either based on the EDIDs if available, or based on the XGA > standards. Our eventual aim is to separate out the connectors from the bridge drivers wherever possible. In the future, a KMS driver using the bridge would be responsible for establishing the links between the bridge and encoder, and the encoder and connector. If in the future we remove the connector pieces from this driver to create a separate generic VGA connector driver, we'll end up with a bridge driver whose main functionality is to convert RGB signals to VGA. The EDID parts would move to the VGA connector driver. In your platform's case, there is no software needed to translate RGB to VGA, but maybe in the future, we might need to add an optional regulator in the driver to support another platform. Therefore, the bridge driver would still be handy to have. Keeping this in consideration, I think this driver (and the DT binding) should be called "dumb-rgb-to-vga-bridge", or "rgb-to-vga-bridge" since that's what the bridge HW primarily does. Thanks, Archit > > Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> > --- > .../bindings/display/bridge/dumb-vga.txt | 54 +++++ > drivers/gpu/drm/bridge/Kconfig | 6 + > drivers/gpu/drm/bridge/Makefile | 1 + > drivers/gpu/drm/bridge/dumb-vga.c | 232 +++++++++++++++++++++ > 4 files changed, 293 insertions(+) > create mode 100644 Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > create mode 100644 drivers/gpu/drm/bridge/dumb-vga.c > > diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > new file mode 100644 > index 000000000000..0056ffa2b31d > --- /dev/null > +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt > @@ -0,0 +1,54 @@ > +Passive RGB to VGA bridge > +------------------------- > + > +This binding is aimed for entirely passive RGB to VGA bridges that do not > +require any configuration. > + > +Required properties: > + > +- compatible: Must be "dumb-vga-bridge" > + > +Required nodes: > + > +This device has two video ports. Their connections are modeled using the OF > +graph bindings specified in Documentation/devicetree/bindings/graph.txt. > + > +- Video port 0 for RGB input > +- Video port 1 for VGA output > + > + > +Example > +------- > + > +bridge { > + compatible = "dumb-vga-bridge"; > + #address-cells = <1>; > + #size-cells = <0>; > + > + ports { > + #address-cells = <1>; > + #size-cells = <0>; > + > + port@0 { > + #address-cells = <1>; > + #size-cells = <0>; > + reg = <0>; > + > + vga_bridge_in: endpoint@0 { > + reg = <0>; > + remote-endpoint = <&tcon0_out_vga>; > + }; > + }; > + > + port@1 { > + #address-cells = <1>; > + #size-cells = <0>; > + reg = <1>; > + > + vga_bridge_out: endpoint@0 { > + reg = <0>; > + remote-endpoint = <&vga_con_in>; > + }; > + }; > + }; > +}; > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig > index a141921445f4..4a6560714397 100644 > --- a/drivers/gpu/drm/bridge/Kconfig > +++ b/drivers/gpu/drm/bridge/Kconfig > @@ -17,6 +17,12 @@ config DRM_ANALOGIX_ANX78XX > the HDMI output of an application processor to MyDP > or DisplayPort. > > +config DRM_DUMB_VGA > + tristate "Dumb RGB to VGA Bridge support" > + select DRM_KMS_HELPER > + help > + Support for passive RGB to VGA bridges > + > config DRM_DW_HDMI > tristate > select DRM_KMS_HELPER > diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile > index bfec9f8cb9d2..413d783828bb 100644 > --- a/drivers/gpu/drm/bridge/Makefile > +++ b/drivers/gpu/drm/bridge/Makefile > @@ -1,6 +1,7 @@ > ccflags-y := -Iinclude/drm > > obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o > +obj-$(CONFIG_DRM_DUMB_VGA) += dumb-vga.o > obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o > obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o > obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o > diff --git a/drivers/gpu/drm/bridge/dumb-vga.c b/drivers/gpu/drm/bridge/dumb-vga.c > new file mode 100644 > index 000000000000..c197be591fb6 > --- /dev/null > +++ b/drivers/gpu/drm/bridge/dumb-vga.c > @@ -0,0 +1,232 @@ > + > +#include <linux/module.h> > +#include <linux/of_graph.h> > + > +#include <drm/drmP.h> > +#include <drm/drm_atomic_helper.h> > +#include <drm/drm_crtc.h> > +#include <drm/drm_crtc_helper.h> > + > +struct dumb_vga { > + struct drm_bridge bridge; > + struct drm_connector connector; > + > + struct i2c_adapter *ddc; > +}; > + > +static inline struct dumb_vga * > +drm_bridge_to_dumb_vga(struct drm_bridge *bridge) > +{ > + return container_of(bridge, struct dumb_vga, bridge); > +} > + > +static inline struct dumb_vga * > +drm_connector_to_dumb_vga(struct drm_connector *connector) > +{ > + return container_of(connector, struct dumb_vga, connector); > +} > + > +static int dumb_vga_get_modes(struct drm_connector *connector) > +{ > + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); > + struct edid *edid; > + int ret; > + > + if (IS_ERR(vga->ddc)) > + goto fallback; > + > + edid = drm_get_edid(connector, vga->ddc); > + if (!edid) { > + DRM_INFO("EDID readout failed, falling back to standard modes\n"); > + goto fallback; > + } > + > + drm_mode_connector_update_edid_property(connector, edid); > + return drm_add_edid_modes(connector, edid); > + > +fallback: > + /* > + * In case we cannot retrieve the EDIDs (broken or missing i2c > + * bus), fallback on the XGA standards > + */ > + ret = drm_add_modes_noedid(connector, 1920, 1200); > + > + /* And prefer a mode pretty much anyone can handle */ > + drm_set_preferred_mode(connector, 1024, 768); > + > + return ret; > +} > + > +static struct drm_encoder * > +dumb_vga_best_encoder(struct drm_connector *connector) > +{ > + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); > + > + return vga->bridge.encoder; > +} > + > +static struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = { > + .get_modes = dumb_vga_get_modes, > + .best_encoder = dumb_vga_best_encoder, > +}; > + > +static enum drm_connector_status > +dumb_vga_connector_detect(struct drm_connector *connector, bool force) > +{ > + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); > + > + /* > + * Even if we have an I2C bus, we can't assume that the cable > + * is disconnected if drm_probe_ddc. Some cables don't wire > + * the DDC pins, or the I2C bus might be disfunctional. > + */ > + if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc)) > + return connector_status_connected; > + > + return connector_status_unknown; > +} > + > +static void > +dumb_vga_connector_destroy(struct drm_connector *connector) > +{ > + drm_connector_cleanup(connector); > +} > + > +static struct drm_connector_funcs dumb_vga_con_funcs = { > + .dpms = drm_atomic_helper_connector_dpms, > + .detect = dumb_vga_connector_detect, > + .fill_modes = drm_helper_probe_single_connector_modes, > + .destroy = dumb_vga_connector_destroy, > + .reset = drm_atomic_helper_connector_reset, > + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state, > + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state, > +}; > + > +static int dumb_vga_attach(struct drm_bridge *bridge) > +{ > + struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge); > + int ret; > + > + if (!bridge->encoder) { > + DRM_ERROR("Missing encoder\n"); > + return -ENODEV; > + } > + > + drm_connector_helper_add(&vga->connector, > + &dumb_vga_con_helper_funcs); > + ret = drm_connector_init(bridge->dev, &vga->connector, > + &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA); > + if (ret) { > + DRM_ERROR("Failed to initialize connector\n"); > + return ret; > + } > + > + drm_mode_connector_attach_encoder(&vga->connector, > + bridge->encoder); > + > + return 0; > +} > + > +static void dumb_vga_nop(struct drm_bridge *bridge) {}; > + > +static struct drm_bridge_funcs dumb_vga_bridge_funcs = { > + .attach = dumb_vga_attach, > + .enable = dumb_vga_nop, > + .disable = dumb_vga_nop, > + .pre_enable = dumb_vga_nop, > + .post_disable = dumb_vga_nop, We don't need to install nops here, the drm bridge core skips calling the op if it can't find it. > +}; > + > +static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev) > +{ > + struct device_node *end_node, *phandle, *remote; > + struct i2c_adapter *ddc; > + > + end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1); > + if (!end_node) { > + dev_err(dev, "Missing connector endpoint\n"); > + return ERR_PTR(-ENODEV); > + } > + > + remote = of_graph_get_remote_port_parent(end_node); > + of_node_put(end_node); > + if (!remote) { > + dev_err(dev, "Enable to parse remote node\n"); > + return ERR_PTR(-EINVAL); > + } > + > + phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0); > + of_node_put(remote); > + if (!phandle) > + return ERR_PTR(-ENODEV); > + > + ddc = of_get_i2c_adapter_by_node(phandle); > + of_node_put(phandle); > + if (!ddc) > + return ERR_PTR(-EPROBE_DEFER); > + > + return ddc; > +} > + > +static int dumb_vga_probe(struct platform_device *pdev) > +{ > + struct dumb_vga *vga; > + int ret; > + > + vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL); > + if (!vga) > + return -ENOMEM; > + platform_set_drvdata(pdev, vga); > + > + vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev); > + if (IS_ERR(vga->ddc)) { > + if (PTR_ERR(vga->ddc) == -ENODEV) { > + dev_info(&pdev->dev, > + "No i2c bus specified... Disabling EDID readout\n"); > + } else { > + dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n"); > + return PTR_ERR(vga->ddc); > + } > + } > + > + vga->bridge.funcs = &dumb_vga_bridge_funcs; > + vga->bridge.of_node = pdev->dev.of_node; > + > + ret = drm_bridge_add(&vga->bridge); > + if (ret && !IS_ERR(vga->ddc)) > + i2c_put_adapter(vga->ddc); > + > + return ret; > +} > + > +static int dumb_vga_remove(struct platform_device *pdev) > +{ > + struct dumb_vga *vga = platform_get_drvdata(pdev); > + > + drm_bridge_remove(&vga->bridge); > + > + if (!IS_ERR(vga->ddc)) > + i2c_put_adapter(vga->ddc); > + > + return 0; > +} > + > +static const struct of_device_id dumb_vga_match[] = { > + { .compatible = "dumb-vga-bridge" }, > + {}, > +}; > +MODULE_DEVICE_TABLE(of, dumb_vga_match); > + > +struct platform_driver dumb_vga_driver = { > + .probe = dumb_vga_probe, > + .remove = dumb_vga_remove, > + .driver = { > + .name = "dumb-vga-bridge", > + .of_match_table = dumb_vga_match, > + }, > +}; > +module_platform_driver(dumb_vga_driver); > + > +MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>"); > +MODULE_DESCRIPTION("Dumb RGB to VGA bridge driver"); > +MODULE_LICENSE("GPL"); >
Hi Archit, On Thu, Jul 21, 2016 at 03:23:18PM +0530, Archit Taneja wrote: > Hi, > > On 07/20/2016 03:28 PM, Maxime Ripard wrote: > >Some boards have an entirely passive RGB to VGA bridge, based on either > >DACs or resistor ladders. > > > >Those might or might not have an i2c bus routed to the VGA connector in > >order to access the screen EDIDs. > > > >Add a bridge that doesn't do anything but expose the modes available on the > >screen, either based on the EDIDs if available, or based on the XGA > >standards. > > Our eventual aim is to separate out the connectors from the bridge > drivers wherever possible. In the future, a KMS driver using the > bridge would be responsible for establishing the links between > the bridge and encoder, and the encoder and connector. > > If in the future we remove the connector pieces from this driver > to create a separate generic VGA connector driver, we'll end up > with a bridge driver whose main functionality is to convert RGB > signals to VGA. The EDID parts would move to the VGA connector > driver. In your platform's case, there is no software needed > to translate RGB to VGA, but maybe in the future, we might need > to add an optional regulator in the driver to support another > platform. Therefore, the bridge driver would still be handy to > have. > > Keeping this in consideration, I think this driver (and the DT > binding) should be called "dumb-rgb-to-vga-bridge", or > "rgb-to-vga-bridge" since that's what the bridge HW primarily > does. That works for me. I'll change it and repost. Thanks! Maxime
diff --git a/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt new file mode 100644 index 000000000000..0056ffa2b31d --- /dev/null +++ b/Documentation/devicetree/bindings/display/bridge/dumb-vga.txt @@ -0,0 +1,54 @@ +Passive RGB to VGA bridge +------------------------- + +This binding is aimed for entirely passive RGB to VGA bridges that do not +require any configuration. + +Required properties: + +- compatible: Must be "dumb-vga-bridge" + +Required nodes: + +This device has two video ports. Their connections are modeled using the OF +graph bindings specified in Documentation/devicetree/bindings/graph.txt. + +- Video port 0 for RGB input +- Video port 1 for VGA output + + +Example +------- + +bridge { + compatible = "dumb-vga-bridge"; + #address-cells = <1>; + #size-cells = <0>; + + ports { + #address-cells = <1>; + #size-cells = <0>; + + port@0 { + #address-cells = <1>; + #size-cells = <0>; + reg = <0>; + + vga_bridge_in: endpoint@0 { + reg = <0>; + remote-endpoint = <&tcon0_out_vga>; + }; + }; + + port@1 { + #address-cells = <1>; + #size-cells = <0>; + reg = <1>; + + vga_bridge_out: endpoint@0 { + reg = <0>; + remote-endpoint = <&vga_con_in>; + }; + }; + }; +}; diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig index a141921445f4..4a6560714397 100644 --- a/drivers/gpu/drm/bridge/Kconfig +++ b/drivers/gpu/drm/bridge/Kconfig @@ -17,6 +17,12 @@ config DRM_ANALOGIX_ANX78XX the HDMI output of an application processor to MyDP or DisplayPort. +config DRM_DUMB_VGA + tristate "Dumb RGB to VGA Bridge support" + select DRM_KMS_HELPER + help + Support for passive RGB to VGA bridges + config DRM_DW_HDMI tristate select DRM_KMS_HELPER diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile index bfec9f8cb9d2..413d783828bb 100644 --- a/drivers/gpu/drm/bridge/Makefile +++ b/drivers/gpu/drm/bridge/Makefile @@ -1,6 +1,7 @@ ccflags-y := -Iinclude/drm obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o +obj-$(CONFIG_DRM_DUMB_VGA) += dumb-vga.o obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o diff --git a/drivers/gpu/drm/bridge/dumb-vga.c b/drivers/gpu/drm/bridge/dumb-vga.c new file mode 100644 index 000000000000..c197be591fb6 --- /dev/null +++ b/drivers/gpu/drm/bridge/dumb-vga.c @@ -0,0 +1,232 @@ + +#include <linux/module.h> +#include <linux/of_graph.h> + +#include <drm/drmP.h> +#include <drm/drm_atomic_helper.h> +#include <drm/drm_crtc.h> +#include <drm/drm_crtc_helper.h> + +struct dumb_vga { + struct drm_bridge bridge; + struct drm_connector connector; + + struct i2c_adapter *ddc; +}; + +static inline struct dumb_vga * +drm_bridge_to_dumb_vga(struct drm_bridge *bridge) +{ + return container_of(bridge, struct dumb_vga, bridge); +} + +static inline struct dumb_vga * +drm_connector_to_dumb_vga(struct drm_connector *connector) +{ + return container_of(connector, struct dumb_vga, connector); +} + +static int dumb_vga_get_modes(struct drm_connector *connector) +{ + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); + struct edid *edid; + int ret; + + if (IS_ERR(vga->ddc)) + goto fallback; + + edid = drm_get_edid(connector, vga->ddc); + if (!edid) { + DRM_INFO("EDID readout failed, falling back to standard modes\n"); + goto fallback; + } + + drm_mode_connector_update_edid_property(connector, edid); + return drm_add_edid_modes(connector, edid); + +fallback: + /* + * In case we cannot retrieve the EDIDs (broken or missing i2c + * bus), fallback on the XGA standards + */ + ret = drm_add_modes_noedid(connector, 1920, 1200); + + /* And prefer a mode pretty much anyone can handle */ + drm_set_preferred_mode(connector, 1024, 768); + + return ret; +} + +static struct drm_encoder * +dumb_vga_best_encoder(struct drm_connector *connector) +{ + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); + + return vga->bridge.encoder; +} + +static struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = { + .get_modes = dumb_vga_get_modes, + .best_encoder = dumb_vga_best_encoder, +}; + +static enum drm_connector_status +dumb_vga_connector_detect(struct drm_connector *connector, bool force) +{ + struct dumb_vga *vga = drm_connector_to_dumb_vga(connector); + + /* + * Even if we have an I2C bus, we can't assume that the cable + * is disconnected if drm_probe_ddc. Some cables don't wire + * the DDC pins, or the I2C bus might be disfunctional. + */ + if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc)) + return connector_status_connected; + + return connector_status_unknown; +} + +static void +dumb_vga_connector_destroy(struct drm_connector *connector) +{ + drm_connector_cleanup(connector); +} + +static struct drm_connector_funcs dumb_vga_con_funcs = { + .dpms = drm_atomic_helper_connector_dpms, + .detect = dumb_vga_connector_detect, + .fill_modes = drm_helper_probe_single_connector_modes, + .destroy = dumb_vga_connector_destroy, + .reset = drm_atomic_helper_connector_reset, + .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state, + .atomic_destroy_state = drm_atomic_helper_connector_destroy_state, +}; + +static int dumb_vga_attach(struct drm_bridge *bridge) +{ + struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge); + int ret; + + if (!bridge->encoder) { + DRM_ERROR("Missing encoder\n"); + return -ENODEV; + } + + drm_connector_helper_add(&vga->connector, + &dumb_vga_con_helper_funcs); + ret = drm_connector_init(bridge->dev, &vga->connector, + &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA); + if (ret) { + DRM_ERROR("Failed to initialize connector\n"); + return ret; + } + + drm_mode_connector_attach_encoder(&vga->connector, + bridge->encoder); + + return 0; +} + +static void dumb_vga_nop(struct drm_bridge *bridge) {}; + +static struct drm_bridge_funcs dumb_vga_bridge_funcs = { + .attach = dumb_vga_attach, + .enable = dumb_vga_nop, + .disable = dumb_vga_nop, + .pre_enable = dumb_vga_nop, + .post_disable = dumb_vga_nop, +}; + +static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev) +{ + struct device_node *end_node, *phandle, *remote; + struct i2c_adapter *ddc; + + end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1); + if (!end_node) { + dev_err(dev, "Missing connector endpoint\n"); + return ERR_PTR(-ENODEV); + } + + remote = of_graph_get_remote_port_parent(end_node); + of_node_put(end_node); + if (!remote) { + dev_err(dev, "Enable to parse remote node\n"); + return ERR_PTR(-EINVAL); + } + + phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0); + of_node_put(remote); + if (!phandle) + return ERR_PTR(-ENODEV); + + ddc = of_get_i2c_adapter_by_node(phandle); + of_node_put(phandle); + if (!ddc) + return ERR_PTR(-EPROBE_DEFER); + + return ddc; +} + +static int dumb_vga_probe(struct platform_device *pdev) +{ + struct dumb_vga *vga; + int ret; + + vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL); + if (!vga) + return -ENOMEM; + platform_set_drvdata(pdev, vga); + + vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev); + if (IS_ERR(vga->ddc)) { + if (PTR_ERR(vga->ddc) == -ENODEV) { + dev_info(&pdev->dev, + "No i2c bus specified... Disabling EDID readout\n"); + } else { + dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n"); + return PTR_ERR(vga->ddc); + } + } + + vga->bridge.funcs = &dumb_vga_bridge_funcs; + vga->bridge.of_node = pdev->dev.of_node; + + ret = drm_bridge_add(&vga->bridge); + if (ret && !IS_ERR(vga->ddc)) + i2c_put_adapter(vga->ddc); + + return ret; +} + +static int dumb_vga_remove(struct platform_device *pdev) +{ + struct dumb_vga *vga = platform_get_drvdata(pdev); + + drm_bridge_remove(&vga->bridge); + + if (!IS_ERR(vga->ddc)) + i2c_put_adapter(vga->ddc); + + return 0; +} + +static const struct of_device_id dumb_vga_match[] = { + { .compatible = "dumb-vga-bridge" }, + {}, +}; +MODULE_DEVICE_TABLE(of, dumb_vga_match); + +struct platform_driver dumb_vga_driver = { + .probe = dumb_vga_probe, + .remove = dumb_vga_remove, + .driver = { + .name = "dumb-vga-bridge", + .of_match_table = dumb_vga_match, + }, +}; +module_platform_driver(dumb_vga_driver); + +MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>"); +MODULE_DESCRIPTION("Dumb RGB to VGA bridge driver"); +MODULE_LICENSE("GPL");
Some boards have an entirely passive RGB to VGA bridge, based on either DACs or resistor ladders. Those might or might not have an i2c bus routed to the VGA connector in order to access the screen EDIDs. Add a bridge that doesn't do anything but expose the modes available on the screen, either based on the EDIDs if available, or based on the XGA standards. Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com> --- .../bindings/display/bridge/dumb-vga.txt | 54 +++++ drivers/gpu/drm/bridge/Kconfig | 6 + drivers/gpu/drm/bridge/Makefile | 1 + drivers/gpu/drm/bridge/dumb-vga.c | 232 +++++++++++++++++++++ 4 files changed, 293 insertions(+) create mode 100644 Documentation/devicetree/bindings/display/bridge/dumb-vga.txt create mode 100644 drivers/gpu/drm/bridge/dumb-vga.c