1 files changed, 318 insertions, 0 deletions
diff --git a/drivers/i2c/busses/i2c-cros-ec-tunnel.c b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
new file mode 100644
index 00000000000..8e7a71487bb
--- /dev/null
+++ b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
@@ -0,0 +1,318 @@
+/*
+ *  Copyright (C) 2013 Google, Inc
+ *
+ *  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.
+ *
+ * Expose an I2C passthrough to the ChromeOS EC.
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/**
+ * struct ec_i2c_device - Driver data for I2C tunnel
+ *
+ * @dev: Device node
+ * @adap: I2C adapter
+ * @ec: Pointer to EC device
+ * @remote_bus: The EC bus number we tunnel to on the other side.
+ * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
+ * @response_buf: Buffer for receiving data; we expect most transfers to fit.
+ */
+
+struct ec_i2c_device {
+	struct device *dev;
+	struct i2c_adapter adap;
+	struct cros_ec_device *ec;
+
+	u16 remote_bus;
+
+	u8 request_buf[256];
+	u8 response_buf[256];
+};
+
+/**
+ * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
+ *
+ * @i2c_msgs: The i2c messages to read
+ * @num: The number of i2c messages.
+ *
+ * Returns the number of bytes the messages will take up.
+ */
+static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
+{
+	int i;
+	int size;
+
+	size = sizeof(struct ec_params_i2c_passthru);
+	size += num * sizeof(struct ec_params_i2c_passthru_msg);
+	for (i = 0; i < num; i++)
+		if (!(i2c_msgs[i].flags & I2C_M_RD))
+			size += i2c_msgs[i].len;
+
+	return size;
+}
+
+/**
+ * ec_i2c_construct_message - construct a message to go to the EC
+ *
+ * This function effectively stuffs the standard i2c_msg format of Linux into
+ * a format that the EC understands.
+ *
+ * @buf: The buffer to fill.  We assume that the buffer is big enough.
+ * @i2c_msgs: The i2c messages to read.
+ * @num: The number of i2c messages.
+ * @bus_num: The remote bus number we want to talk to.
+ *
+ * Returns 0 or a negative error number.
+ */
+static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
+				    int num, u16 bus_num)
+{
+	struct ec_params_i2c_passthru *params;
+	u8 *out_data;
+	int i;
+
+	out_data = buf + sizeof(struct ec_params_i2c_passthru) +
+		   num * sizeof(struct ec_params_i2c_passthru_msg);
+
+	params = (struct ec_params_i2c_passthru *)buf;
+	params->port = bus_num;
+	params->num_msgs = num;
+	for (i = 0; i < num; i++) {
+		const struct i2c_msg *i2c_msg = &i2c_msgs[i];
+		struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
+
+		msg->len = i2c_msg->len;
+		msg->addr_flags = i2c_msg->addr;
+
+		if (i2c_msg->flags & I2C_M_TEN)
+			msg->addr_flags |= EC_I2C_FLAG_10BIT;
+
+		if (i2c_msg->flags & I2C_M_RD) {
+			msg->addr_flags |= EC_I2C_FLAG_READ;
+		} else {
+			memcpy(out_data, i2c_msg->buf, msg->len);
+			out_data += msg->len;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
+ *
+ * @i2c_msgs: The i2c messages to to fill up.
+ * @num: The number of i2c messages expected.
+ *
+ * Returns the number of response bytes expeced.
+ */
+static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
+{
+	int size;
+	int i;
+
+	size = sizeof(struct ec_response_i2c_passthru);
+	for (i = 0; i < num; i++)
+		if (i2c_msgs[i].flags & I2C_M_RD)
+			size += i2c_msgs[i].len;
+
+	return size;
+}
+
+/**
+ * ec_i2c_parse_response - Parse a response from the EC
+ *
+ * We'll take the EC's response and copy it back into msgs.
+ *
+ * @buf: The buffer to parse.
+ * @i2c_msgs: The i2c messages to to fill up.
+ * @num: The number of i2c messages; will be modified to include the actual
+ *	 number received.
+ *
+ * Returns 0 or a negative error number.
+ */
+static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
+				 int *num)
+{
+	const struct ec_response_i2c_passthru *resp;
+	const u8 *in_data;
+	int i;
+
+	in_data = buf + sizeof(struct ec_response_i2c_passthru);
+
+	resp = (const struct ec_response_i2c_passthru *)buf;
+	if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
+		return -ETIMEDOUT;
+	else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
+		return -EREMOTEIO;
+
+	/* Other side could send us back fewer messages, but not more */
+	if (resp->num_msgs > *num)
+		return -EPROTO;
+	*num = resp->num_msgs;
+
+	for (i = 0; i < *num; i++) {
+		struct i2c_msg *i2c_msg = &i2c_msgs[i];
+
+		if (i2c_msgs[i].flags & I2C_M_RD) {
+			memcpy(i2c_msg->buf, in_data, i2c_msg->len);
+			in_data += i2c_msg->len;
+		}
+	}
+
+	return 0;
+}
+
+static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
+		       int num)
+{
+	struct ec_i2c_device *bus = adap->algo_data;
+	struct device *dev = bus->dev;
+	const u16 bus_num = bus->remote_bus;
+	int request_len;
+	int response_len;
+	u8 *request = NULL;
+	u8 *response = NULL;
+	int result;
+
+	request_len = ec_i2c_count_message(i2c_msgs, num);
+	if (request_len < 0) {
+		dev_warn(dev, "Error constructing message %d\n", request_len);
+		result = request_len;
+		goto exit;
+	}
+	response_len = ec_i2c_count_response(i2c_msgs, num);
+	if (response_len < 0) {
+		/* Unexpected; no errors should come when NULL response */
+		dev_warn(dev, "Error preparing response %d\n", response_len);
+		result = response_len;
+		goto exit;
+	}
+
+	if (request_len <= ARRAY_SIZE(bus->request_buf)) {
+		request = bus->request_buf;
+	} else {
+		request = kzalloc(request_len, GFP_KERNEL);
+		if (request == NULL) {
+			result = -ENOMEM;
+			goto exit;
+		}
+	}
+	if (response_len <= ARRAY_SIZE(bus->response_buf)) {
+		response = bus->response_buf;
+	} else {
+		response = kzalloc(response_len, GFP_KERNEL);
+		if (response == NULL) {
+			result = -ENOMEM;
+			goto exit;
+		}
+	}
+
+	ec_i2c_construct_message(request, i2c_msgs, num, bus_num);
+	result = bus->ec->command_sendrecv(bus->ec, EC_CMD_I2C_PASSTHRU,
+					   request, request_len,
+					   response, response_len);
+	if (result)
+		goto exit;
+
+	result = ec_i2c_parse_response(response, i2c_msgs, &num);
+	if (result < 0)
+		goto exit;
+
+	/* Indicate success by saying how many messages were sent */
+	result = num;
+exit:
+	if (request != bus->request_buf)
+		kfree(request);
+	if (response != bus->response_buf)
+		kfree(response);
+
+	return result;
+}
+
+static u32 ec_i2c_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm ec_i2c_algorithm = {
+	.master_xfer	= ec_i2c_xfer,
+	.functionality	= ec_i2c_functionality,
+};
+
+static int ec_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
+	struct device *dev = &pdev->dev;
+	struct ec_i2c_device *bus = NULL;
+	u32 remote_bus;
+	int err;
+
+	if (!ec->command_sendrecv) {
+		dev_err(dev, "Missing sendrecv\n");
+		return -EINVAL;
+	}
+
+	bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
+	if (bus == NULL)
+		return -ENOMEM;
+
+	err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
+	if (err) {
+		dev_err(dev, "Couldn't read remote-bus property\n");
+		return err;
+	}
+	bus->remote_bus = remote_bus;
+
+	bus->ec = ec;
+	bus->dev = dev;
+
+	bus->adap.owner = THIS_MODULE;
+	strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
+	bus->adap.algo = &ec_i2c_algorithm;
+	bus->adap.algo_data = bus;
+	bus->adap.dev.parent = &pdev->dev;
+	bus->adap.dev.of_node = np;
+
+	err = i2c_add_adapter(&bus->adap);
+	if (err) {
+		dev_err(dev, "cannot register i2c adapter\n");
+		return err;
+	}
+	platform_set_drvdata(pdev, bus);
+
+	return err;
+}
+
+static int ec_i2c_remove(struct platform_device *dev)
+{
+	struct ec_i2c_device *bus = platform_get_drvdata(dev);
+
+	i2c_del_adapter(&bus->adap);
+
+	return 0;
+}
+
+static struct platform_driver ec_i2c_tunnel_driver = {
+	.probe = ec_i2c_probe,
+	.remove = ec_i2c_remove,
+	.driver = {
+		.name = "cros-ec-i2c-tunnel",
+	},
+};
+
+module_platform_driver(ec_i2c_tunnel_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("EC I2C tunnel driver");
+MODULE_ALIAS("platform:cros-ec-i2c-tunnel");