[PATCH 1/3] video: add simple, transparent, bridge implementation

[Ahmad Fatoum]

This enables support for simple bridges, i.e. bridges that can be
used without initialization.

This is e.g. the case with bridges that have persistent configuration,
the kernel has a full-fledged driver to configure the bridge and persist it.

The bootloader then needs to do nothing more. Having such a transparent
bridge allows reusing the kernel device tree without changing the graph
specification.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 .../video/display/bridge/simple-bridge.txt    | 41 +++++++++++++
 drivers/video/Kconfig                         |  7 +++
 drivers/video/Makefile                        |  2 +-
 drivers/video/simple-bridge.c                 | 57 +++++++++++++++++++
 4 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/video/display/bridge/simple-bridge.txt
 create mode 100644 drivers/video/simple-bridge.c

diff --git a/Documentation/devicetree/bindings/video/display/bridge/simple-bridge.txt b/Documentation/devicetree/bindings/video/display/bridge/simple-bridge.txt
new file mode 100644
index 000000000000..b1485569d992
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/display/bridge/simple-bridge.txt
@@ -0,0 +1,41 @@
+Simple display bridge
+=====================
+
+bridge node
+-----------
+
+Required properties:
+	- compatible : "barebox,simple-bridge".
+	- #address-cells : must be <1>
+	- #size-cells : must be <0>
+	- video interfaces: Device node should contain two video interface port
+			    nodes for input and output according to [1].
+			    - port at 0 - bridge input
+			    - port at 1 - bridge output
+
+[1]: dts/Bindings/media/video-interfaces.txt
+
+
+Example:
+	fpga-display-bridge at 0 {
+		compatible = "barebox,simple-bridge";
+		reg = <0>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		port at 0 {
+			reg = <0>;
+
+			ch0_lcd_in: endpoint {
+				remote-endpoint = <&parallel_display_out>;
+			};
+		};
+
+		port at 1 {
+			reg = <1>;
+
+			ch0_out: endpoint {
+				remote-endpoint = <&disp1_in>;
+			};
+		};
+	};
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index a26bace176a1..b153978492a9 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -161,4 +161,11 @@ config DRIVER_VIDEO_SIMPLE_PANEL
 	  Linux Kernel implementation this one is able to understand display-timings
 	  nodes so that it's not necessary to keep a list of all known displays
 	  with their corresponding timings in barebox.
+
+config DRIVER_VIDEO_SIMPLE_BRIDGE
+	bool "Simple bridge support"
+	depends on OFTREE
+	help
+	  This enables support for simple bridges, i.e. bridges that can be
+	  used without initialization.
 endif
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 01fabe880920..2296c14ccc73 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -24,4 +24,4 @@ obj-$(CONFIG_DRIVER_VIDEO_IMX_IPUV3) += imx-ipu-v3/
 obj-$(CONFIG_DRIVER_VIDEO_EFI_GOP) += efi_gop.o
 obj-$(CONFIG_DRIVER_VIDEO_FB_SSD1307) += ssd1307fb.o
 obj-$(CONFIG_BACKLIGHT_RAVE_SP)	+= rave-sp-backlight.o
-
+obj-$(CONFIG_DRIVER_VIDEO_SIMPLE_BRIDGE)	+= simple-bridge.o
diff --git a/drivers/video/simple-bridge.c b/drivers/video/simple-bridge.c
new file mode 100644
index 000000000000..0d6621df7b0c
--- /dev/null
+++ b/drivers/video/simple-bridge.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// SPDX-FileCopyright-Text: 2020 Pengutronix, Ahmad Fatoum <a.fatoum at pengutronix.de>
+
+#include <common.h>
+#include <init.h>
+#include <driver.h>
+#include <video/vpl.h>
+#include <of_graph.h>
+
+enum { BRIDGE_INPUT_PORT = 0, BRIDGE_OUTPUT_PORT = 1 };
+
+struct simple_bridge_priv {
+	struct device_d	*dev;
+	struct vpl	vpl;
+};
+
+static int simple_bridge_ioctl(struct vpl *vpl, unsigned int port,
+			       unsigned int cmd, void *ptr)
+{
+	struct simple_bridge_priv *priv = container_of(vpl, struct simple_bridge_priv, vpl);
+
+	dev_dbg(priv->dev, "ioctl(port=%d, cmd=0x%08x)\n", port, cmd);
+
+	return vpl_ioctl(vpl, BRIDGE_OUTPUT_PORT, cmd, ptr);
+}
+
+static int simple_bridge_probe(struct device_d *dev)
+{
+	struct simple_bridge_priv *priv;
+	struct device_node *port;
+
+	priv = xzalloc(sizeof(*priv));
+	priv->dev = dev;
+
+	port = of_graph_get_port_by_id(dev->device_node, BRIDGE_OUTPUT_PORT);
+	if (!port) {
+		dev_err(dev, "No remote panel found\n");
+		return -ENODEV;
+	}
+
+	priv->vpl.node = dev->device_node;
+	priv->vpl.ioctl = simple_bridge_ioctl;
+
+	return vpl_register(&priv->vpl);
+}
+
+static const struct of_device_id __maybe_unused simple_bridge_match[] = {
+	{ .compatible = "barebox,simple-bridge" },
+	{ /* sentinel */ },
+};
+
+static struct driver_d simple_bridge_driver = {
+	.name		= "simple-bridge",
+	.probe		= simple_bridge_probe,
+	.of_compatible	= DRV_OF_COMPAT(simple_bridge_match),
+};
+device_platform_driver(simple_bridge_driver);
-- 
2.28.0