[mirror_ubuntu-artful-kernel.git] / drivers / hid / hid-cp2112.c

/*
 * 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 %zd 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 < %zd\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__); \
} \
static 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) \
static 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");