HID: add hid-cp2112 driver

This patch adds support for the Silicon Labs CP2112 "Single-Chip HID USB to
SMBus Master Bridge."

This is a HID device driver which registers as an i2c adapter and gpiochip to
expose these functions of the CP2112. The customizable USB descriptor fields
are exposed as sysfs attributes.  The SMBus byte-read, byte-data-read/write,
and word-data-read transfer modes have been tested by talking to an i2c
sensor.  The GPIO functions and USB descriptor field programming have also
been tested.

Signed-off-by: David Barksdale <dbarksdale@uplogix.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 1066 insertions, 0 deletions

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
new file mode 100644
index 000000000000..ca0f356a2384
--- /dev/null
+++ b/drivers/hid/hid-cp2112.c
@@ -0,0 +1,1066 @@
+/*
+ * hid-cp2112.c - Silicon Labs HID USB to SMBus master bridge
+ * Copyright (c) 2013,2014 Uplogix, Inc.
+ * David Barksdale <dbarksdale@uplogix.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ */
+
+/*
+ * The Silicon Labs CP2112 chip is a USB HID device which provides an
+ * SMBus controller for talking to slave devices and 8 GPIO pins. The
+ * host communicates with the CP2112 via raw HID reports.
+ *
+ * Data Sheet:
+ *   http://www.silabs.com/Support%20Documents/TechnicalDocs/CP2112.pdf
+ * Programming Interface Specification:
+ *   http://www.silabs.com/Support%20Documents/TechnicalDocs/AN495.pdf
+ */
+
+#include <linux/gpio.h>
+#include <linux/hid.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/nls.h>
+#include <linux/usb/ch9.h>
+#include "hid-ids.h"
+
+enum {
+	CP2112_GPIO_CONFIG		= 0x02,
+	CP2112_GPIO_GET			= 0x03,
+	CP2112_GPIO_SET			= 0x04,
+	CP2112_GET_VERSION_INFO		= 0x05,
+	CP2112_SMBUS_CONFIG		= 0x06,
+	CP2112_DATA_READ_REQUEST	= 0x10,
+	CP2112_DATA_WRITE_READ_REQUEST	= 0x11,
+	CP2112_DATA_READ_FORCE_SEND	= 0x12,
+	CP2112_DATA_READ_RESPONSE	= 0x13,
+	CP2112_DATA_WRITE_REQUEST	= 0x14,
+	CP2112_TRANSFER_STATUS_REQUEST	= 0x15,
+	CP2112_TRANSFER_STATUS_RESPONSE	= 0x16,
+	CP2112_CANCEL_TRANSFER		= 0x17,
+	CP2112_LOCK_BYTE		= 0x20,
+	CP2112_USB_CONFIG		= 0x21,
+	CP2112_MANUFACTURER_STRING	= 0x22,
+	CP2112_PRODUCT_STRING		= 0x23,
+	CP2112_SERIAL_STRING		= 0x24,
+};
+
+enum {
+	STATUS0_IDLE		= 0x00,
+	STATUS0_BUSY		= 0x01,
+	STATUS0_COMPLETE	= 0x02,
+	STATUS0_ERROR		= 0x03,
+};
+
+enum {
+	STATUS1_TIMEOUT_NACK		= 0x00,
+	STATUS1_TIMEOUT_BUS		= 0x01,
+	STATUS1_ARBITRATION_LOST	= 0x02,
+	STATUS1_READ_INCOMPLETE		= 0x03,
+	STATUS1_WRITE_INCOMPLETE	= 0x04,
+	STATUS1_SUCCESS			= 0x05,
+};
+
+struct cp2112_smbus_config_report {
+	u8 report;		/* CP2112_SMBUS_CONFIG */
+	__be32 clock_speed;	/* Hz */
+	u8 device_address;	/* Stored in the upper 7 bits */
+	u8 auto_send_read;	/* 1 = enabled, 0 = disabled */
+	__be16 write_timeout;	/* ms, 0 = no timeout */
+	__be16 read_timeout;	/* ms, 0 = no timeout */
+	u8 scl_low_timeout;	/* 1 = enabled, 0 = disabled */
+	__be16 retry_time;	/* # of retries, 0 = no limit */
+} __packed;
+
+struct cp2112_usb_config_report {
+	u8 report;	/* CP2112_USB_CONFIG */
+	__le16 vid;	/* Vendor ID */
+	__le16 pid;	/* Product ID */
+	u8 max_power;	/* Power requested in 2mA units */
+	u8 power_mode;	/* 0x00 = bus powered
+			   0x01 = self powered & regulator off
+			   0x02 = self powered & regulator on */
+	u8 release_major;
+	u8 release_minor;
+	u8 mask;	/* What fields to program */
+} __packed;
+
+struct cp2112_read_req_report {
+	u8 report;	/* CP2112_DATA_READ_REQUEST */
+	u8 slave_address;
+	__be16 length;
+} __packed;
+
+struct cp2112_write_read_req_report {
+	u8 report;	/* CP2112_DATA_WRITE_READ_REQUEST */
+	u8 slave_address;
+	__be16 length;
+	u8 target_address_length;
+	u8 target_address[16];
+} __packed;
+
+struct cp2112_write_req_report {
+	u8 report;	/* CP2112_DATA_WRITE_REQUEST */
+	u8 slave_address;
+	u8 length;
+	u8 data[61];
+} __packed;
+
+struct cp2112_force_read_report {
+	u8 report;	/* CP2112_DATA_READ_FORCE_SEND */
+	__be16 length;
+} __packed;
+
+struct cp2112_xfer_status_report {
+	u8 report;	/* CP2112_TRANSFER_STATUS_RESPONSE */
+	u8 status0;	/* STATUS0_* */
+	u8 status1;	/* STATUS1_* */
+	__be16 retries;
+	__be16 length;
+} __packed;
+
+struct cp2112_string_report {
+	u8 dummy;		/* force .string to be aligned */
+	u8 report;		/* CP2112_*_STRING */
+	u8 length;		/* length in bytes of everyting after .report */
+	u8 type;		/* USB_DT_STRING */
+	wchar_t string[30];	/* UTF16_LITTLE_ENDIAN string */
+} __packed;
+
+/* Number of times to request transfer status before giving up waiting for a
+   transfer to complete. This may need to be changed if SMBUS clock, retries,
+   or read/write/scl_low timeout settings are changed. */
+static const int XFER_STATUS_RETRIES = 10;
+
+/* Time in ms to wait for a CP2112_DATA_READ_RESPONSE or
+   CP2112_TRANSFER_STATUS_RESPONSE. */
+static const int RESPONSE_TIMEOUT = 50;
+
+static const struct hid_device_id cp2112_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CYGNAL, USB_DEVICE_ID_CYGNAL_CP2112) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, cp2112_devices);
+
+struct cp2112_device {
+	struct i2c_adapter adap;
+	struct hid_device *hdev;
+	wait_queue_head_t wait;
+	u8 read_data[61];
+	u8 read_length;
+	int xfer_status;
+	atomic_t read_avail;
+	atomic_t xfer_avail;
+	struct gpio_chip gc;
+};
+
+static int gpio_push_pull = 0xFF;
+module_param(gpio_push_pull, int, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(gpio_push_pull, "GPIO push-pull configuration bitmask");
+
+static int cp2112_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
+{
+	struct cp2112_device *dev = container_of(chip, struct cp2112_device,
+						 gc);
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[5];
+	int ret;
+
+	ret = hdev->hid_get_raw_report(hdev, CP2112_GPIO_CONFIG, buf,
+				       sizeof(buf), HID_FEATURE_REPORT);
+	if (ret != sizeof(buf)) {
+		hid_err(hdev, "error requesting GPIO config: %d\n", ret);
+		return ret;
+	}
+
+	buf[1] &= ~(1 << offset);
+	buf[2] = gpio_push_pull;
+
+	ret = hdev->hid_output_raw_report(hdev, buf, sizeof(buf),
+					  HID_FEATURE_REPORT);
+	if (ret < 0) {
+		hid_err(hdev, "error setting GPIO config: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void cp2112_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+	struct cp2112_device *dev = container_of(chip, struct cp2112_device,
+						 gc);
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[3];
+	int ret;
+
+	buf[0] = CP2112_GPIO_SET;
+	buf[1] = value ? 0xff : 0;
+	buf[2] = 1 << offset;
+
+	ret = hdev->hid_output_raw_report(hdev, buf, sizeof(buf),
+					  HID_FEATURE_REPORT);
+	if (ret < 0)
+		hid_err(hdev, "error setting GPIO values: %d\n", ret);
+}
+
+static int cp2112_gpio_get(struct gpio_chip *chip, unsigned offset)
+{
+	struct cp2112_device *dev = container_of(chip, struct cp2112_device,
+						 gc);
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[2];
+	int ret;
+
+	ret = hdev->hid_get_raw_report(hdev, CP2112_GPIO_GET, buf, sizeof(buf),
+				       HID_FEATURE_REPORT);
+	if (ret != sizeof(buf)) {
+		hid_err(hdev, "error requesting GPIO values: %d\n", ret);
+		return ret;
+	}
+
+	return (buf[1] >> offset) & 1;
+}
+
+static int cp2112_gpio_direction_output(struct gpio_chip *chip,
+					unsigned offset, int value)
+{
+	struct cp2112_device *dev = container_of(chip, struct cp2112_device,
+						 gc);
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[5];
+	int ret;
+
+	cp2112_gpio_set(chip, offset, value);
+
+	ret = hdev->hid_get_raw_report(hdev, CP2112_GPIO_CONFIG, buf,
+				       sizeof(buf), HID_FEATURE_REPORT);
+	if (ret != sizeof(buf)) {
+		hid_err(hdev, "error requesting GPIO config: %d\n", ret);
+		return ret;
+	}
+
+	buf[1] |= 1 << offset;
+	buf[2] = gpio_push_pull;
+
+	ret = hdev->hid_output_raw_report(hdev, buf, sizeof(buf),
+					  HID_FEATURE_REPORT);
+	if (ret < 0) {
+		hid_err(hdev, "error setting GPIO config: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int cp2112_hid_get(struct hid_device *hdev, unsigned char report_number,
+			  u8 *data, size_t count, unsigned char report_type)
+{
+	u8 *buf;
+	int ret;
+
+	buf = kmalloc(count, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = hdev->hid_get_raw_report(hdev, report_number, buf, count,
+				       report_type);
+	memcpy(data, buf, count);
+	kfree(buf);
+	return ret;
+}
+
+static int cp2112_hid_output(struct hid_device *hdev, u8 *data, size_t count,
+			     unsigned char report_type)
+{
+	u8 *buf;
+	int ret;
+
+	buf = kmemdup(data, count, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	ret = hdev->hid_output_raw_report(hdev, buf, count, report_type);
+	kfree(buf);
+	return ret;
+}
+
+static int cp2112_wait(struct cp2112_device *dev, atomic_t *avail)
+{
+	int ret = 0;
+
+	/* We have sent either a CP2112_TRANSFER_STATUS_REQUEST or a
+	 * CP2112_DATA_READ_FORCE_SEND and we are waiting for the response to
+	 * come in cp2112_raw_event or timeout. There will only be one of these
+	 * in flight at any one time. The timeout is extremely large and is a
+	 * last resort if the CP2112 has died. If we do timeout we don't expect
+	 * to receive the response which would cause data races, it's not like
+	 * we can do anything about it anyway.
+	 */
+	ret = wait_event_interruptible_timeout(dev->wait,
+		atomic_read(avail), msecs_to_jiffies(RESPONSE_TIMEOUT));
+	if (-ERESTARTSYS == ret)
+		return ret;
+	if (!ret)
+		return -ETIMEDOUT;
+
+	atomic_set(avail, 0);
+	return 0;
+}
+
+static int cp2112_xfer_status(struct cp2112_device *dev)
+{
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[2];
+	int ret;
+
+	buf[0] = CP2112_TRANSFER_STATUS_REQUEST;
+	buf[1] = 0x01;
+	atomic_set(&dev->xfer_avail, 0);
+
+	ret = cp2112_hid_output(hdev, buf, 2, HID_OUTPUT_REPORT);
+	if (ret < 0) {
+		hid_warn(hdev, "Error requesting status: %d\n", ret);
+		return ret;
+	}
+
+	ret = cp2112_wait(dev, &dev->xfer_avail);
+	if (ret)
+		return ret;
+
+	return dev->xfer_status;
+}
+
+static int cp2112_read(struct cp2112_device *dev, u8 *data, size_t size)
+{
+	struct hid_device *hdev = dev->hdev;
+	struct cp2112_force_read_report report;
+	int ret;
+
+	report.report = CP2112_DATA_READ_FORCE_SEND;
+	report.length = cpu_to_be16(size);
+
+	atomic_set(&dev->read_avail, 0);
+
+	ret = cp2112_hid_output(hdev, &report.report, sizeof(report),
+				HID_OUTPUT_REPORT);
+	if (ret < 0) {
+		hid_warn(hdev, "Error requesting data: %d\n", ret);
+		return ret;
+	}
+
+	ret = cp2112_wait(dev, &dev->read_avail);
+	if (ret)
+		return ret;
+
+	hid_dbg(hdev, "read %d of %d bytes requested\n",
+		dev->read_length, size);
+
+	if (size > dev->read_length)
+		size = dev->read_length;
+
+	memcpy(data, dev->read_data, size);
+	return dev->read_length;
+}
+
+static int cp2112_read_req(void *buf, u8 slave_address, u16 length)
+{
+	struct cp2112_read_req_report *report = buf;
+
+	if (length < 1 || length > 512)
+		return -EINVAL;
+
+	report->report = CP2112_DATA_READ_REQUEST;
+	report->slave_address = slave_address << 1;
+	report->length = cpu_to_be16(length);
+	return sizeof(*report);
+}
+
+static int cp2112_write_read_req(void *buf, u8 slave_address, u16 length,
+				 u8 command, u8 *data, u8 data_length)
+{
+	struct cp2112_write_read_req_report *report = buf;
+
+	if (length < 1 || length > 512
+	    || data_length > sizeof(report->target_address) - 1)
+		return -EINVAL;
+
+	report->report = CP2112_DATA_WRITE_READ_REQUEST;
+	report->slave_address = slave_address << 1;
+	report->length = cpu_to_be16(length);
+	report->target_address_length = data_length + 1;
+	report->target_address[0] = command;
+	memcpy(&report->target_address[1], data, data_length);
+	return data_length + 6;
+}
+
+static int cp2112_write_req(void *buf, u8 slave_address, u8 command, u8 *data,
+			    u8 data_length)
+{
+	struct cp2112_write_req_report *report = buf;
+
+	if (data_length > sizeof(report->data) - 1)
+		return -EINVAL;
+
+	report->report = CP2112_DATA_WRITE_REQUEST;
+	report->slave_address = slave_address << 1;
+	report->length = data_length + 1;
+	report->data[0] = command;
+	memcpy(&report->data[1], data, data_length);
+	return data_length + 4;
+}
+
+static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
+		       unsigned short flags, char read_write, u8 command,
+		       int size, union i2c_smbus_data *data)
+{
+	struct cp2112_device *dev = (struct cp2112_device *)adap->algo_data;
+	struct hid_device *hdev = dev->hdev;
+	u8 buf[64];
+	__be16 word;
+	size_t count;
+	size_t read_length = 0;
+	unsigned int retries;
+	int ret;
+
+	hid_dbg(hdev, "%s addr 0x%x flags 0x%x cmd 0x%x size %d\n",
+		read_write == I2C_SMBUS_WRITE ? "write" : "read",
+		addr, flags, command, size);
+
+	switch (size) {
+	case I2C_SMBUS_BYTE:
+		read_length = 1;
+
+		if (I2C_SMBUS_READ == read_write)
+			count = cp2112_read_req(buf, addr, read_length);
+		else
+			count = cp2112_write_req(buf, addr, data->byte, NULL,
+						 0);
+		break;
+	case I2C_SMBUS_BYTE_DATA:
+		read_length = 1;
+
+		if (I2C_SMBUS_READ == read_write)
+			count = cp2112_write_read_req(buf, addr, read_length,
+						      command, NULL, 0);
+		else
+			count = cp2112_write_req(buf, addr, command,
+						 &data->byte, 1);
+		break;
+	case I2C_SMBUS_WORD_DATA:
+		read_length = 2;
+		word = cpu_to_be16(data->word);
+
+		if (I2C_SMBUS_READ == read_write)
+			count = cp2112_write_read_req(buf, addr, read_length,
+						      command, NULL, 0);
+		else
+			count = cp2112_write_req(buf, addr, command,
+						 (u8 *)&word, 2);
+		break;
+	case I2C_SMBUS_PROC_CALL:
+		size = I2C_SMBUS_WORD_DATA;
+		read_write = I2C_SMBUS_READ;
+		read_length = 2;
+		word = cpu_to_be16(data->word);
+
+		count = cp2112_write_read_req(buf, addr, read_length, command,
+					      (u8 *)&word, 2);
+		break;
+	case I2C_SMBUS_I2C_BLOCK_DATA:
+		size = I2C_SMBUS_BLOCK_DATA;
+		/* fallthrough */
+	case I2C_SMBUS_BLOCK_DATA:
+		if (I2C_SMBUS_READ == read_write) {
+			count = cp2112_write_read_req(buf, addr,
+						      I2C_SMBUS_BLOCK_MAX,
+						      command, NULL, 0);
+		} else {
+			count = cp2112_write_req(buf, addr, command,
+						 data->block,
+						 data->block[0] + 1);
+		}
+		break;
+	case I2C_SMBUS_BLOCK_PROC_CALL:
+		size = I2C_SMBUS_BLOCK_DATA;
+		read_write = I2C_SMBUS_READ;
+
+		count = cp2112_write_read_req(buf, addr, I2C_SMBUS_BLOCK_MAX,
+					      command, data->block,
+					      data->block[0] + 1);
+		break;
+	default:
+		hid_warn(hdev, "Unsupported transaction %d\n", size);
+		return -EOPNOTSUPP;
+	}
+
+	if (count < 0)
+		return count;
+
+	ret = hid_hw_power(hdev, PM_HINT_FULLON);
+	if (ret < 0) {
+		hid_err(hdev, "power management error: %d\n", ret);
+		return ret;
+	}
+
+	ret = cp2112_hid_output(hdev, buf, count, HID_OUTPUT_REPORT);
+	if (ret < 0) {
+		hid_warn(hdev, "Error starting transaction: %d\n", ret);
+		goto power_normal;
+	}
+
+	for (retries = 0; retries < XFER_STATUS_RETRIES; ++retries) {
+		ret = cp2112_xfer_status(dev);
+		if (-EBUSY == ret)
+			continue;
+		if (ret < 0)
+			goto power_normal;
+		break;
+	}
+
+	if (XFER_STATUS_RETRIES <= retries) {
+		hid_warn(hdev, "Transfer timed out, cancelling.\n");
+		buf[0] = CP2112_CANCEL_TRANSFER;
+		buf[1] = 0x01;
+
+		ret = cp2112_hid_output(hdev, buf, 2, HID_OUTPUT_REPORT);
+		if (ret < 0)
+			hid_warn(hdev, "Error cancelling transaction: %d\n",
+				 ret);
+
+		ret = -ETIMEDOUT;
+		goto power_normal;
+	}
+
+	if (I2C_SMBUS_WRITE == read_write) {
+		ret = 0;
+		goto power_normal;
+	}
+
+	if (I2C_SMBUS_BLOCK_DATA == size)
+		read_length = ret;
+
+	ret = cp2112_read(dev, buf, read_length);
+	if (ret < 0)
+		goto power_normal;
+	if (ret != read_length) {
+		hid_warn(hdev, "short read: %d < %d\n", ret, read_length);
+		ret = -EIO;
+		goto power_normal;
+	}
+
+	switch (size) {
+	case I2C_SMBUS_BYTE:
+	case I2C_SMBUS_BYTE_DATA:
+		data->byte = buf[0];
+		break;
+	case I2C_SMBUS_WORD_DATA:
+		data->word = be16_to_cpup((__be16 *)buf);
+		break;
+	case I2C_SMBUS_BLOCK_DATA:
+		if (read_length > I2C_SMBUS_BLOCK_MAX) {
+			ret = -EPROTO;
+			goto power_normal;
+		}
+
+		memcpy(data->block, buf, read_length);
+		break;
+	}
+
+	ret = 0;
+power_normal:
+	hid_hw_power(hdev, PM_HINT_NORMAL);
+	hid_dbg(hdev, "transfer finished: %d\n", ret);
+	return ret;
+}
+
+static u32 cp2112_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_SMBUS_BYTE |
+		I2C_FUNC_SMBUS_BYTE_DATA |
+		I2C_FUNC_SMBUS_WORD_DATA |
+		I2C_FUNC_SMBUS_BLOCK_DATA |
+		I2C_FUNC_SMBUS_I2C_BLOCK |
+		I2C_FUNC_SMBUS_PROC_CALL |
+		I2C_FUNC_SMBUS_BLOCK_PROC_CALL;
+}
+
+static const struct i2c_algorithm smbus_algorithm = {
+	.smbus_xfer	= cp2112_xfer,
+	.functionality	= cp2112_functionality,
+};
+
+static int cp2112_get_usb_config(struct hid_device *hdev,
+				 struct cp2112_usb_config_report *cfg)
+{
+	int ret;
+
+	ret = cp2112_hid_get(hdev, CP2112_USB_CONFIG, (u8 *)cfg, sizeof(*cfg),
+			     HID_FEATURE_REPORT);
+	if (ret != sizeof(*cfg)) {
+		hid_err(hdev, "error reading usb config: %d\n", ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int cp2112_set_usb_config(struct hid_device *hdev,
+				 struct cp2112_usb_config_report *cfg)
+{
+	int ret;
+
+	BUG_ON(cfg->report != CP2112_USB_CONFIG);
+
+	ret = cp2112_hid_output(hdev, (u8 *)cfg, sizeof(*cfg),
+				HID_FEATURE_REPORT);
+	if (ret != sizeof(*cfg)) {
+		hid_err(hdev, "error writing usb config: %d\n", ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static void chmod_sysfs_attrs(struct hid_device *hdev);
+
+#define CP2112_CONFIG_ATTR(name, store, format, ...) \
+static ssize_t name##_store(struct device *kdev, \
+			    struct device_attribute *attr, const char *buf, \
+			    size_t count) \
+{ \
+	struct hid_device *hdev = container_of(kdev, struct hid_device, dev); \
+	struct cp2112_usb_config_report cfg; \
+	int ret = cp2112_get_usb_config(hdev, &cfg); \
+	if (ret) \
+		return ret; \
+	store; \
+	ret = cp2112_set_usb_config(hdev, &cfg); \
+	if (ret) \
+		return ret; \
+	chmod_sysfs_attrs(hdev); \
+	return count; \
+} \
+static ssize_t name##_show(struct device *kdev, \
+			   struct device_attribute *attr, char *buf) \
+{ \
+	struct hid_device *hdev = container_of(kdev, struct hid_device, dev); \
+	struct cp2112_usb_config_report cfg; \
+	int ret = cp2112_get_usb_config(hdev, &cfg); \
+	if (ret) \
+		return ret; \
+	return scnprintf(buf, PAGE_SIZE, format, ##__VA_ARGS__); \
+} \
+DEVICE_ATTR_RW(name);
+
+CP2112_CONFIG_ATTR(vendor_id, ({
+	u16 vid;
+
+	if (sscanf(buf, "%hi", &vid) != 1)
+		return -EINVAL;
+
+	cfg.vid = cpu_to_le16(vid);
+	cfg.mask = 0x01;
+}), "0x%04x\n", le16_to_cpu(cfg.vid));
+
+CP2112_CONFIG_ATTR(product_id, ({
+	u16 pid;
+
+	if (sscanf(buf, "%hi", &pid) != 1)
+		return -EINVAL;
+
+	cfg.pid = cpu_to_le16(pid);
+	cfg.mask = 0x02;
+}), "0x%04x\n", le16_to_cpu(cfg.pid));
+
+CP2112_CONFIG_ATTR(max_power, ({
+	int mA;
+
+	if (sscanf(buf, "%i", &mA) != 1)
+		return -EINVAL;
+
+	cfg.max_power = (mA + 1) / 2;
+	cfg.mask = 0x04;
+}), "%u mA\n", cfg.max_power * 2);
+
+CP2112_CONFIG_ATTR(power_mode, ({
+	if (sscanf(buf, "%hhi", &cfg.power_mode) != 1)
+		return -EINVAL;
+
+	cfg.mask = 0x08;
+}), "%u\n", cfg.power_mode);
+
+CP2112_CONFIG_ATTR(release_version, ({
+	if (sscanf(buf, "%hhi.%hhi", &cfg.release_major, &cfg.release_minor)
+	    != 2)
+		return -EINVAL;
+
+	cfg.mask = 0x10;
+}), "%u.%u\n", cfg.release_major, cfg.release_minor);
+
+#undef CP2112_CONFIG_ATTR
+
+struct cp2112_pstring_attribute {
+	struct device_attribute attr;
+	unsigned char report;
+};
+
+static ssize_t pstr_store(struct device *kdev,
+			  struct device_attribute *kattr, const char *buf,
+			  size_t count)
+{
+	struct hid_device *hdev = container_of(kdev, struct hid_device, dev);
+	struct cp2112_pstring_attribute *attr =
+		container_of(kattr, struct cp2112_pstring_attribute, attr);
+	struct cp2112_string_report report;
+	int ret;
+
+	memset(&report, 0, sizeof(report));
+
+	ret = utf8s_to_utf16s(buf, count, UTF16_LITTLE_ENDIAN,
+			      report.string, ARRAY_SIZE(report.string));
+	report.report = attr->report;
+	report.length = ret * sizeof(report.string[0]) + 2;
+	report.type = USB_DT_STRING;
+
+	ret = cp2112_hid_output(hdev, &report.report, report.length + 1,
+				HID_FEATURE_REPORT);
+	if (ret != report.length + 1) {
+		hid_err(hdev, "error writing %s string: %d\n", kattr->attr.name,
+			ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	chmod_sysfs_attrs(hdev);
+	return count;
+}
+
+static ssize_t pstr_show(struct device *kdev,
+			 struct device_attribute *kattr, char *buf)
+{
+	struct hid_device *hdev = container_of(kdev, struct hid_device, dev);
+	struct cp2112_pstring_attribute *attr =
+		container_of(kattr, struct cp2112_pstring_attribute, attr);
+	struct cp2112_string_report report;
+	u8 length;
+	int ret;
+
+	ret = cp2112_hid_get(hdev, attr->report, &report.report,
+			     sizeof(report) - 1, HID_FEATURE_REPORT);
+	if (ret < 3) {
+		hid_err(hdev, "error reading %s string: %d\n", kattr->attr.name,
+			ret);
+		if (ret < 0)
+			return ret;
+		return -EIO;
+	}
+
+	if (report.length < 2) {
+		hid_err(hdev, "invalid %s string length: %d\n",
+			kattr->attr.name, report.length);
+		return -EIO;
+	}
+
+	length = report.length > ret - 1 ? ret - 1 : report.length;
+	length = (length - 2) / sizeof(report.string[0]);
+	ret = utf16s_to_utf8s(report.string, length, UTF16_LITTLE_ENDIAN, buf,
+			      PAGE_SIZE - 1);
+	buf[ret++] = '\n';
+	return ret;
+}
+
+#define CP2112_PSTR_ATTR(name, _report) \
+struct cp2112_pstring_attribute dev_attr_##name = { \
+	.attr = __ATTR(name, (S_IWUSR | S_IRUGO), pstr_show, pstr_store), \
+	.report = _report, \
+};
+
+CP2112_PSTR_ATTR(manufacturer,	CP2112_MANUFACTURER_STRING);
+CP2112_PSTR_ATTR(product,	CP2112_PRODUCT_STRING);
+CP2112_PSTR_ATTR(serial,	CP2112_SERIAL_STRING);
+
+#undef CP2112_PSTR_ATTR
+
+static const struct attribute_group cp2112_attr_group = {
+	.attrs = (struct attribute *[]){
+		&dev_attr_vendor_id.attr,
+		&dev_attr_product_id.attr,
+		&dev_attr_max_power.attr,
+		&dev_attr_power_mode.attr,
+		&dev_attr_release_version.attr,
+		&dev_attr_manufacturer.attr.attr,
+		&dev_attr_product.attr.attr,
+		&dev_attr_serial.attr.attr,
+		NULL
+	}
+};
+
+/* Chmoding our sysfs attributes is simply a way to expose which fields in the
+ * PROM have already been programmed. We do not depend on this preventing
+ * writing to these attributes since the CP2112 will simply ignore writes to
+ * already-programmed fields. This is why there is no sense in fixing this
+ * racy behaviour.
+ */
+static void chmod_sysfs_attrs(struct hid_device *hdev)
+{
+	struct attribute **attr;
+	u8 buf[2];
+	int ret;
+
+	ret = cp2112_hid_get(hdev, CP2112_LOCK_BYTE, buf, sizeof(buf),
+			     HID_FEATURE_REPORT);
+	if (ret != sizeof(buf)) {
+		hid_err(hdev, "error reading lock byte: %d\n", ret);
+		return;
+	}
+
+	for (attr = cp2112_attr_group.attrs; *attr; ++attr) {
+		umode_t mode = (buf[1] & 1) ? S_IWUSR | S_IRUGO : S_IRUGO;
+		ret = sysfs_chmod_file(&hdev->dev.kobj, *attr, mode);
+		if (ret < 0)
+			hid_err(hdev, "error chmoding sysfs file %s\n",
+				(*attr)->name);
+		buf[1] >>= 1;
+	}
+}
+
+static int cp2112_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct cp2112_device *dev;
+	u8 buf[3];
+	struct cp2112_smbus_config_report config;
+	int ret;
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_open(hdev);
+	if (ret) {
+		hid_err(hdev, "hw open failed\n");
+		goto err_hid_stop;
+	}
+
+	ret = hid_hw_power(hdev, PM_HINT_FULLON);
+	if (ret < 0) {
+		hid_err(hdev, "power management error: %d\n", ret);
+		goto err_hid_close;
+	}
+
+	ret = cp2112_hid_get(hdev, CP2112_GET_VERSION_INFO, buf, sizeof(buf),
+			     HID_FEATURE_REPORT);
+	if (ret != sizeof(buf)) {
+		hid_err(hdev, "error requesting version\n");
+		if (ret >= 0)
+			ret = -EIO;
+		goto err_power_normal;
+	}
+
+	hid_info(hdev, "Part Number: 0x%02X Device Version: 0x%02X\n",
+		 buf[1], buf[2]);
+
+	ret = cp2112_hid_get(hdev, CP2112_SMBUS_CONFIG, (u8 *)&config,
+			     sizeof(config), HID_FEATURE_REPORT);
+	if (ret != sizeof(config)) {
+		hid_err(hdev, "error requesting SMBus config\n");
+		if (ret >= 0)
+			ret = -EIO;
+		goto err_power_normal;
+	}
+
+	config.retry_time = cpu_to_be16(1);
+
+	ret = cp2112_hid_output(hdev, (u8 *)&config, sizeof(config),
+				HID_FEATURE_REPORT);
+	if (ret != sizeof(config)) {
+		hid_err(hdev, "error setting SMBus config\n");
+		if (ret >= 0)
+			ret = -EIO;
+		goto err_power_normal;
+	}
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev) {
+		ret = -ENOMEM;
+		goto err_power_normal;
+	}
+
+	hid_set_drvdata(hdev, (void *)dev);
+	dev->hdev		= hdev;
+	dev->adap.owner		= THIS_MODULE;
+	dev->adap.class		= I2C_CLASS_HWMON;
+	dev->adap.algo		= &smbus_algorithm;
+	dev->adap.algo_data	= dev;
+	dev->adap.dev.parent	= &hdev->dev;
+	snprintf(dev->adap.name, sizeof(dev->adap.name),
+		 "CP2112 SMBus Bridge on hiddev%d", hdev->minor);
+	init_waitqueue_head(&dev->wait);
+
+	hid_device_io_start(hdev);
+	ret = i2c_add_adapter(&dev->adap);
+	hid_device_io_stop(hdev);
+
+	if (ret) {
+		hid_err(hdev, "error registering i2c adapter\n");
+		goto err_free_dev;
+	}
+
+	hid_dbg(hdev, "adapter registered\n");
+
+	dev->gc.label			= "cp2112_gpio";
+	dev->gc.direction_input		= cp2112_gpio_direction_input;
+	dev->gc.direction_output	= cp2112_gpio_direction_output;
+	dev->gc.set			= cp2112_gpio_set;
+	dev->gc.get			= cp2112_gpio_get;
+	dev->gc.base			= -1;
+	dev->gc.ngpio			= 8;
+	dev->gc.can_sleep		= 1;
+	dev->gc.dev			= &hdev->dev;
+
+	ret = gpiochip_add(&dev->gc);
+	if (ret < 0) {
+		hid_err(hdev, "error registering gpio chip\n");
+		goto err_free_i2c;
+	}
+
+	ret = sysfs_create_group(&hdev->dev.kobj, &cp2112_attr_group);
+	if (ret < 0) {
+		hid_err(hdev, "error creating sysfs attrs\n");
+		goto err_gpiochip_remove;
+	}
+
+	chmod_sysfs_attrs(hdev);
+	hid_hw_power(hdev, PM_HINT_NORMAL);
+
+	return ret;
+
+err_gpiochip_remove:
+	if (gpiochip_remove(&dev->gc) < 0)
+		hid_err(hdev, "error removing gpio chip\n");
+err_free_i2c:
+	i2c_del_adapter(&dev->adap);
+err_free_dev:
+	kfree(dev);
+err_power_normal:
+	hid_hw_power(hdev, PM_HINT_NORMAL);
+err_hid_close:
+	hid_hw_close(hdev);
+err_hid_stop:
+	hid_hw_stop(hdev);
+	return ret;
+}
+
+static void cp2112_remove(struct hid_device *hdev)
+{
+	struct cp2112_device *dev = hid_get_drvdata(hdev);
+
+	sysfs_remove_group(&hdev->dev.kobj, &cp2112_attr_group);
+	if (gpiochip_remove(&dev->gc))
+		hid_err(hdev, "unable to remove gpio chip\n");
+	i2c_del_adapter(&dev->adap);
+	/* i2c_del_adapter has finished removing all i2c devices from our
+	 * adapter. Well behaved devices should no longer call our cp2112_xfer
+	 * and should have waited for any pending calls to finish. It has also
+	 * waited for device_unregister(&adap->dev) to complete. Therefore we
+	 * can safely free our struct cp2112_device.
+	 */
+	hid_hw_close(hdev);
+	hid_hw_stop(hdev);
+	kfree(dev);
+}
+
+static int cp2112_raw_event(struct hid_device *hdev, struct hid_report *report,
+			    u8 *data, int size)
+{
+	struct cp2112_device *dev = hid_get_drvdata(hdev);
+	struct cp2112_xfer_status_report *xfer = (void *)data;
+
+	switch (data[0]) {
+	case CP2112_TRANSFER_STATUS_RESPONSE:
+		hid_dbg(hdev, "xfer status: %02x %02x %04x %04x\n",
+			xfer->status0, xfer->status1,
+			be16_to_cpu(xfer->retries), be16_to_cpu(xfer->length));
+
+		switch (xfer->status0) {
+		case STATUS0_IDLE:
+			dev->xfer_status = -EAGAIN;
+			break;
+		case STATUS0_BUSY:
+			dev->xfer_status = -EBUSY;
+			break;
+		case STATUS0_COMPLETE:
+			dev->xfer_status = be16_to_cpu(xfer->length);
+			break;
+		case STATUS0_ERROR:
+			switch (xfer->status1) {
+			case STATUS1_TIMEOUT_NACK:
+			case STATUS1_TIMEOUT_BUS:
+				dev->xfer_status = -ETIMEDOUT;
+				break;
+			default:
+				dev->xfer_status = -EIO;
+				break;
+			}
+			break;
+		default:
+			dev->xfer_status = -EINVAL;
+			break;
+		}
+
+		atomic_set(&dev->xfer_avail, 1);
+		break;
+	case CP2112_DATA_READ_RESPONSE:
+		hid_dbg(hdev, "read response: %02x %02x\n", data[1], data[2]);
+
+		dev->read_length = data[2];
+		if (dev->read_length > sizeof(dev->read_data))
+			dev->read_length = sizeof(dev->read_data);
+
+		memcpy(dev->read_data, &data[3], dev->read_length);
+		atomic_set(&dev->read_avail, 1);
+		break;
+	default:
+		hid_err(hdev, "unknown report\n");
+
+		return 0;
+	}
+
+	wake_up_interruptible(&dev->wait);
+	return 1;
+}
+
+static struct hid_driver cp2112_driver = {
+	.name		= "cp2112",
+	.id_table	= cp2112_devices,
+	.probe		= cp2112_probe,
+	.remove		= cp2112_remove,
+	.raw_event	= cp2112_raw_event,
+};
+
+module_hid_driver(cp2112_driver);
+MODULE_DESCRIPTION("Silicon Labs HID USB to SMBus master bridge");
+MODULE_AUTHOR("David Barksdale <dbarksdale@uplogix.com>");
+MODULE_LICENSE("GPL");
+