[PATCH 02/10] Input: synaptics-rmi4: Add I2C transport driver

[Andrew Duggan <aduggan@synaptics.com>]

Add the transport driver for devices using RMI4 over I2C.

Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
Signed-off-by: Christopher Heiny <cheiny@synaptics.com>
---
 drivers/input/rmi4/Kconfig   |  11 ++
 drivers/input/rmi4/Makefile  |   3 +
 drivers/input/rmi4/rmi_i2c.c | 260 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 274 insertions(+)
 create mode 100644 drivers/input/rmi4/rmi_i2c.c

diff --git a/drivers/input/rmi4/Kconfig b/drivers/input/rmi4/Kconfig
index 45a9ff4..e1c07fc 100644
--- a/drivers/input/rmi4/Kconfig
+++ b/drivers/input/rmi4/Kconfig
@@ -24,3 +24,14 @@ config RMI4_DEBUG
 	  if you are actively developing/debugging RMI4 features.
 
 	  If unsure, say N.
+
+config RMI4_I2C
+	tristate "RMI4 I2C Support"
+	depends on RMI4_CORE && I2C
+	help
+	  Say Y here if you want to support RMI4 devices connected to an I2C
+	  bus.
+
+	  If unsure, say Y.
+
+	  This feature is not currently available as a loadable module.
diff --git a/drivers/input/rmi4/Makefile b/drivers/input/rmi4/Makefile
index b33768f..0bb318d 100644
--- a/drivers/input/rmi4/Makefile
+++ b/drivers/input/rmi4/Makefile
@@ -1,4 +1,7 @@
 obj-$(CONFIG_RMI4_CORE) += rmi_core.o
 rmi_core-y := rmi_bus.o rmi_driver.o rmi_f01.o
 
+# Transports
+obj-$(CONFIG_RMI4_I2C) += rmi_i2c.o
+
 ccflags-$(CONFIG_RMI4_DEBUG) += -DDEBUG
diff --git a/drivers/input/rmi4/rmi_i2c.c b/drivers/input/rmi4/rmi_i2c.c
new file mode 100644
index 0000000..c6e680d
--- /dev/null
+++ b/drivers/input/rmi4/rmi_i2c.c
@@ -0,0 +1,260 @@
+/*
+ * Copyright (c) 2011-2015 Synaptics Incorporated
+ * Copyright (c) 2011 Unixphere
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/i2c.h>
+#include <linux/rmi.h>
+#include "rmi_driver.h"
+
+#define BUFFER_SIZE_INCREMENT 32
+
+/**
+ * struct rmi_i2c_xport - stores information for i2c communication
+ *
+ * @xport: The transport interface structure
+ *
+ * @page_mutex: Locks current page to avoid changing pages in unexpected ways.
+ * @page: Keeps track of the current virtual page
+ *
+ * @tx_buf: Buffer used for transmitting data to the sensor over i2c.
+ * @tx_buf_size: Size of the buffer
+ */
+struct rmi_i2c_xport {
+	struct rmi_transport_dev xport;
+	struct i2c_client *client;
+
+	struct mutex page_mutex;
+	int page;
+
+	u8 *tx_buf;
+	size_t tx_buf_size;
+};
+
+#define RMI_PAGE_SELECT_REGISTER 0xff
+#define RMI_I2C_PAGE(addr) (((addr) >> 8) & 0xff)
+
+/*
+ * rmi_set_page - Set RMI page
+ * @xport: The pointer to the rmi_transport_dev struct
+ * @page: The new page address.
+ *
+ * RMI devices have 16-bit addressing, but some of the transport
+ * implementations (like SMBus) only have 8-bit addressing. So RMI implements
+ * a page address at 0xff of every page so we can reliable page addresses
+ * every 256 registers.
+ *
+ * The page_mutex lock must be held when this function is entered.
+ *
+ * Returns zero on success, non-zero on failure.
+ */
+static int rmi_set_page(struct rmi_i2c_xport *rmi_i2c, u8 page)
+{
+	struct i2c_client *client = rmi_i2c->client;
+	u8 txbuf[2] = {RMI_PAGE_SELECT_REGISTER, page};
+	int retval;
+
+	retval = i2c_master_send(client, txbuf, sizeof(txbuf));
+	if (retval != sizeof(txbuf)) {
+		dev_err(&client->dev,
+			"%s: set page failed: %d.", __func__, retval);
+		return (retval < 0) ? retval : -EIO;
+	}
+
+	rmi_i2c->page = page;
+	return 0;
+}
+
+static int rmi_i2c_write_block(struct rmi_transport_dev *xport, u16 addr,
+			       const void *buf, size_t len)
+{
+	struct rmi_i2c_xport *rmi_i2c =
+		container_of(xport, struct rmi_i2c_xport, xport);
+	struct i2c_client *client = rmi_i2c->client;
+	size_t tx_size = len + 1;
+	int retval;
+
+	mutex_lock(&rmi_i2c->page_mutex);
+
+	if (!rmi_i2c->tx_buf || rmi_i2c->tx_buf_size < tx_size) {
+		if (rmi_i2c->tx_buf)
+			devm_kfree(&client->dev, rmi_i2c->tx_buf);
+		rmi_i2c->tx_buf_size = tx_size + BUFFER_SIZE_INCREMENT;
+		rmi_i2c->tx_buf = devm_kzalloc(&client->dev,
+					       rmi_i2c->tx_buf_size,
+					       GFP_KERNEL);
+		if (!rmi_i2c->tx_buf) {
+			rmi_i2c->tx_buf_size = 0;
+			retval = -ENOMEM;
+			goto exit;
+		}
+	}
+
+	rmi_i2c->tx_buf[0] = addr & 0xff;
+	memcpy(rmi_i2c->tx_buf + 1, buf, len);
+
+	if (RMI_I2C_PAGE(addr) != rmi_i2c->page) {
+		retval = rmi_set_page(rmi_i2c, RMI_I2C_PAGE(addr));
+		if (retval)
+			goto exit;
+	}
+
+	retval = i2c_master_send(client, rmi_i2c->tx_buf, tx_size);
+	if (retval == tx_size)
+		retval = 0;
+	else if (retval >= 0)
+		retval = -EIO;
+
+exit:
+	dev_dbg(&client->dev,
+		"write %zd bytes at %#06x: %d (%*ph)\n",
+		len, addr, retval, (int)len, buf);
+
+	mutex_unlock(&rmi_i2c->page_mutex);
+	return retval;
+}
+
+static int rmi_i2c_read_block(struct rmi_transport_dev *xport, u16 addr,
+			      void *buf, size_t len)
+{
+	struct rmi_i2c_xport *rmi_i2c =
+		container_of(xport, struct rmi_i2c_xport, xport);
+	struct i2c_client *client = rmi_i2c->client;
+	u8 addr_offset = addr & 0xff;
+	int retval;
+	struct i2c_msg msgs[] = {
+		{
+			.addr	= client->addr,
+			.len	= sizeof(addr_offset),
+			.buf	= &addr_offset,
+		},
+		{
+			.addr	= client->addr,
+			.flags	= I2C_M_RD,
+			.len	= len,
+			.buf	= buf,
+		},
+	};
+
+	mutex_lock(&rmi_i2c->page_mutex);
+
+	if (RMI_I2C_PAGE(addr) != rmi_i2c->page) {
+		retval = rmi_set_page(rmi_i2c, RMI_I2C_PAGE(addr));
+		if (retval)
+			goto exit;
+	}
+
+	retval = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (retval == ARRAY_SIZE(msgs))
+		retval = 0; /* success */
+	else if (retval >= 0)
+		retval = -EIO;
+
+exit:
+	dev_dbg(&client->dev,
+		"read %zd bytes at %#06x: %d (%*ph)\n",
+		len, addr, retval, (int)len, buf);
+
+	mutex_unlock(&rmi_i2c->page_mutex);
+	return retval;
+}
+
+static const struct rmi_transport_ops rmi_i2c_ops = {
+	.write_block	= rmi_i2c_write_block,
+	.read_block	= rmi_i2c_read_block,
+};
+
+static int rmi_i2c_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct rmi_device_platform_data *pdata;
+	struct rmi_device_platform_data *client_pdata =
+					dev_get_platdata(&client->dev);
+	struct rmi_i2c_xport *rmi_i2c;
+	int retval;
+
+	rmi_i2c = devm_kzalloc(&client->dev, sizeof(struct rmi_i2c_xport),
+				GFP_KERNEL);
+	if (!rmi_i2c)
+		return -ENOMEM;
+
+	pdata = &rmi_i2c->xport.pdata;
+
+	if (client_pdata)
+		*pdata = *client_pdata;
+
+	dev_dbg(&client->dev, "Probing %s.\n", dev_name(&client->dev));
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
+		dev_err(&client->dev,
+			"adapter does not support required functionality.\n");
+		return -ENODEV;
+	}
+
+	rmi_i2c->client = client;
+	mutex_init(&rmi_i2c->page_mutex);
+
+	rmi_i2c->xport.dev = &client->dev;
+	rmi_i2c->xport.proto_name = "i2c";
+	rmi_i2c->xport.ops = &rmi_i2c_ops;
+	rmi_i2c->xport.irq = client->irq;
+	rmi_i2c->xport.irq_flags = pdata->irq_flags;
+
+	/*
+	 * Setting the page to zero will (a) make sure the PSR is in a
+	 * known state, and (b) make sure we can talk to the device.
+	 */
+	retval = rmi_set_page(rmi_i2c, 0);
+	if (retval) {
+		dev_err(&client->dev, "Failed to set page select to 0.\n");
+		return retval;
+	}
+
+	retval = rmi_register_transport_device(&rmi_i2c->xport);
+	if (retval) {
+		dev_err(&client->dev, "Failed to register transport driver at 0x%.2X.\n",
+			client->addr);
+		return retval;
+	}
+
+	i2c_set_clientdata(client, rmi_i2c);
+
+	dev_info(&client->dev, "registered rmi i2c driver at %#04x.\n",
+			client->addr);
+	return 0;
+}
+
+static int rmi_i2c_remove(struct i2c_client *client)
+{
+	struct rmi_i2c_xport *rmi_i2c = i2c_get_clientdata(client);
+
+	rmi_unregister_transport_device(&rmi_i2c->xport);
+
+	return 0;
+}
+
+static const struct i2c_device_id rmi_id[] = {
+	{ "rmi_i2c", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, rmi_id);
+
+static struct i2c_driver rmi_i2c_driver = {
+	.driver = {
+		.owner	= THIS_MODULE,
+		.name	= "rmi_i2c",
+	},
+	.id_table	= rmi_id,
+	.probe		= rmi_i2c_probe,
+	.remove		= rmi_i2c_remove,
+};
+
+module_i2c_driver(rmi_i2c_driver);
+
+MODULE_AUTHOR("Christopher Heiny <cheiny@synaptics.com>");
+MODULE_DESCRIPTION("RMI I2C driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION(RMI_DRIVER_VERSION);
-- 
2.5.0