i2c: sw-edid: add a driver which simulates edid

This adds a driver which simulates a i2c bus with an attached EDID
memory. The memory content is read from the device tree.
This allows to simulate EDID data which may differ from an attached
display.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Dominik Sliwa <dominik.sliwa@toradex.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>

3 files changed, 175 insertions, 1 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 1c0b382ccc41..05c4266d8d92 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -708,6 +708,13 @@ config I2C_STU300
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-stu300.
 
+config I2C_SW_EDID
+	tristate "Simulated I2C adapter serving EDID data from the device tree"
+	help
+	  If you say yes to this option, support will be included for a
+	  simulated I2C adapter simulating an attached EDID memory @ 0x50.
+	  The EDID data is taken from the device tree.
+
 config I2C_TEGRA
 	tristate "NVIDIA Tegra internal I2C controller"
 	depends on ARCH_TEGRA
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 04fb39ed83b4..f978bd649b28 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -69,7 +69,8 @@ obj-$(CONFIG_I2C_SH7760)	+= i2c-sh7760.o
 obj-$(CONFIG_I2C_SH_MOBILE)	+= i2c-sh_mobile.o
 obj-$(CONFIG_I2C_SIMTEC)	+= i2c-simtec.o
 obj-$(CONFIG_I2C_SIRF)		+= i2c-sirf.o
-obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
+obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.
+obj-$(CONFIG_I2C_SW_EDID)	+= i2c-sw-edid.o
 CFLAGS_i2c-tegra.o		 = -Werror
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 CFLAGS_i2c-slave-tegra.o	 = -Werror
diff --git a/drivers/i2c/busses/i2c-sw-edid.c b/drivers/i2c/busses/i2c-sw-edid.c
new file mode 100644
index 000000000000..66c1885c843f
--- /dev/null
+++ b/drivers/i2c/busses/i2c-sw-edid.c
@@ -0,0 +1,166 @@
+/*
+ *	Copyright (C) 2018 Toradex AG
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version 2
+ *	of the License, or (at your option) any later version.
+ *
+ *	This program is distributed in the hope that it will be useful,
+ *	but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *	GNU General Public License for more details.
+ *
+ *	Simulated I2C adapter which provides EDID data out of the device tree.
+ */
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+
+/* This will be the driver name the kernel reports */
+#define DRIVER_NAME "i2c-sw-edid"
+
+struct i2c_sw_edid_struct {
+	struct i2c_adapter	adapter;
+	unsigned char		edid_data[512];
+};
+
+static const struct of_device_id i2c_sw_edid_dt_ids[] = {
+	{ .compatible = "sw-edid", .data = 0, },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, i2c_sw_edid_dt_ids);
+
+static int i2c_sw_edid_xfer(struct i2c_adapter *adapter,
+						struct i2c_msg *msgs, int num)
+{
+	static int data_ptr = 0;
+	unsigned int i;
+	int result = -EINVAL;
+	struct i2c_sw_edid_struct *i2c_sw_edid = i2c_get_adapdata(adapter);
+
+	dev_dbg(&i2c_sw_edid->adapter.dev, "<%s>\n", __func__);
+
+	/* read/write data */
+	for (i = 0; i < num; i++) {
+		result = 0;
+
+		/* we only simulate I2C device 0x50 */
+		if(msgs[i].addr != 0x50) {
+			result = -ENXIO;
+			goto out;
+		} else if (msgs[i].flags & I2C_M_RD) {
+			if ((data_ptr + msgs[i].len) >
+			    sizeof(i2c_sw_edid->edid_data)) {
+				result = -EINVAL;
+				goto out;
+			}
+			memcpy(msgs[i].buf, &(i2c_sw_edid->edid_data[data_ptr]),
+			       msgs[i].len);
+			data_ptr += msgs[i].len;
+		} else {
+			if (msgs[i].len == 1)
+				data_ptr = msgs[i].buf[0];
+		}
+	}
+out:
+	dev_dbg(&i2c_sw_edid->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
+		(result < 0) ? "error" : "success msg",
+			(result < 0) ? result : num);
+	return (result < 0) ? result : num;
+}
+
+static u32 i2c_sw_edid_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
+		| I2C_FUNC_SMBUS_READ_BLOCK_DATA;
+}
+
+static struct i2c_algorithm i2c_sw_edid_algo = {
+	.master_xfer	= i2c_sw_edid_xfer,
+	.functionality	= i2c_sw_edid_func,
+};
+
+static int i2c_sw_edid_probe(struct platform_device *pdev)
+{
+	struct i2c_sw_edid_struct *i2c_sw_edid;
+	int lenp, ret;
+
+	dev_dbg(&pdev->dev, "<%s>\n", __func__);
+
+	i2c_sw_edid = devm_kzalloc(&pdev->dev, sizeof(*i2c_sw_edid),
+				   GFP_KERNEL);
+	if (!i2c_sw_edid)
+		return -ENOMEM;
+
+	/* Setup i2c_sw_edid driver structure */
+	strlcpy(i2c_sw_edid->adapter.name, pdev->name,
+		sizeof(i2c_sw_edid->adapter.name));
+	i2c_sw_edid->adapter.owner		= THIS_MODULE;
+	i2c_sw_edid->adapter.algo		= &i2c_sw_edid_algo;
+	i2c_sw_edid->adapter.dev.parent		= &pdev->dev;
+	i2c_sw_edid->adapter.nr			= pdev->id;
+	i2c_sw_edid->adapter.dev.of_node	= pdev->dev.of_node;
+
+	/* Get EDID data */
+	(void) of_find_property(pdev->dev.of_node,"edid-data", &lenp);
+	lenp = min(lenp, (int)sizeof(i2c_sw_edid->edid_data));
+
+	of_property_read_u8_array(pdev->dev.of_node, "edid-data",
+		&i2c_sw_edid->edid_data[0], lenp);
+
+	/* Set up adapter data */
+	i2c_set_adapdata(&i2c_sw_edid->adapter, i2c_sw_edid);
+
+	/* Set up platform driver data */
+	platform_set_drvdata(pdev, i2c_sw_edid);
+
+	/* Add I2C adapter */
+	ret = i2c_add_numbered_adapter(&i2c_sw_edid->adapter);
+	if (ret < 0)
+		return ret;
+
+	dev_info(&i2c_sw_edid->adapter.dev, "SW EDID I2C adapter registered\n");
+
+	return 0;   /* Return OK */
+}
+
+static int i2c_sw_edid_remove(struct platform_device *pdev)
+{
+	struct i2c_sw_edid_struct *i2c_sw_edid = platform_get_drvdata(pdev);
+
+	/* remove adapter */
+	dev_dbg(&i2c_sw_edid->adapter.dev, "adapter removed\n");
+	i2c_del_adapter(&i2c_sw_edid->adapter);
+
+	return 0;
+}
+
+static struct platform_driver i2c_sw_edid_driver = {
+	.probe = i2c_sw_edid_probe,
+	.remove = i2c_sw_edid_remove,
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = i2c_sw_edid_dt_ids,
+	},
+};
+
+static int __init i2c_adap_sw_edid_init(void)
+{
+	return platform_driver_register(&i2c_sw_edid_driver);
+}
+subsys_initcall(i2c_adap_sw_edid_init);
+
+static void __exit i2c_adap_sw_edid_exit(void)
+{
+	platform_driver_unregister(&i2c_sw_edid_driver);
+}
+module_exit(i2c_adap_sw_edid_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Max Krummenacher");
+MODULE_DESCRIPTION("Simulated I2C adapter serving EDID data from the device tree");
+MODULE_ALIAS("platform:" DRIVER_NAME);