HSI: hsi_char: Add HSI char device driver

Add HSI char device driver to the kernel.

Signed-off-by: Andras Domokos <andras.domokos@nokia.com>
Signed-off-by: Carlos Chinea <carlos.chinea@nokia.com>

2 files changed, 865 insertions, 0 deletions

diff --git a/drivers/hsi/clients/hsi_char.c b/drivers/hsi/clients/hsi_char.c
new file mode 100644
index 000000000000..88a050df2389
--- /dev/null
+++ b/drivers/hsi/clients/hsi_char.c
@@ -0,0 +1,802 @@
+/*
+ * HSI character device driver, implements the character device
+ * interface.
+ *
+ * Copyright (C) 2010 Nokia Corporation. All rights reserved.
+ *
+ * Contact: Andras Domokos <andras.domokos@nokia.com>
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/kmemleak.h>
+#include <linux/ioctl.h>
+#include <linux/wait.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/uaccess.h>
+#include <linux/scatterlist.h>
+#include <linux/stat.h>
+#include <linux/hsi/hsi.h>
+#include <linux/hsi/hsi_char.h>
+
+#define HSC_DEVS                16 /* Num of channels */
+#define HSC_MSGS                4
+
+#define HSC_RXBREAK             0
+
+#define HSC_ID_BITS             6
+#define HSC_PORT_ID_BITS        4
+#define HSC_ID_MASK             3
+#define HSC_PORT_ID_MASK        3
+#define HSC_CH_MASK             0xf
+
+/*
+ * We support up to 4 controllers that can have up to 4
+ * ports, which should currently be more than enough.
+ */
+#define HSC_BASEMINOR(id, port_id) \
+                ((((id) & HSC_ID_MASK) << HSC_ID_BITS) | \
+                (((port_id) & HSC_PORT_ID_MASK) << HSC_PORT_ID_BITS))
+
+enum {
+        HSC_CH_OPEN,
+        HSC_CH_READ,
+        HSC_CH_WRITE,
+        HSC_CH_WLINE,
+};
+
+enum {
+        HSC_RX,
+        HSC_TX,
+};
+
+struct hsc_client_data;
+/**
+ * struct hsc_channel - hsi_char internal channel data
+ * @ch: channel number
+ * @flags: Keeps state of the channel (open/close, reading, writing)
+ * @free_msgs_list: List of free HSI messages/requests
+ * @rx_msgs_queue: List of pending RX requests
+ * @tx_msgs_queue: List of pending TX requests
+ * @lock: Serialize access to the lists
+ * @cl: reference to the associated hsi_client
+ * @cl_data: reference to the client data that this channels belongs to
+ * @rx_wait: RX requests wait queue
+ * @tx_wait: TX requests wait queue
+ */
+struct hsc_channel {
+        unsigned int            ch;
+        unsigned long           flags;
+        struct list_head        free_msgs_list;
+        struct list_head        rx_msgs_queue;
+        struct list_head        tx_msgs_queue;
+        spinlock_t              lock;
+        struct hsi_client       *cl;
+        struct hsc_client_data *cl_data;
+        wait_queue_head_t       rx_wait;
+        wait_queue_head_t       tx_wait;
+};
+
+/**
+ * struct hsc_client_data - hsi_char internal client data
+ * @cdev: Characther device associated to the hsi_client
+ * @lock: Lock to serialize open/close access
+ * @flags: Keeps track of port state (rx hwbreak armed)
+ * @usecnt: Use count for claiming the HSI port (mutex protected)
+ * @cl: Referece to the HSI client
+ * @channels: Array of channels accessible by the client
+ */
+struct hsc_client_data {
+        struct cdev             cdev;
+        struct mutex            lock;
+        unsigned long           flags;
+        unsigned int            usecnt;
+        struct hsi_client       *cl;
+        struct hsc_channel      channels[HSC_DEVS];
+};
+
+/* Stores the major number dynamically allocated for hsi_char */
+static unsigned int hsc_major;
+/* Maximum buffer size that hsi_char will accept from userspace */
+static unsigned int max_data_size = 0x1000;
+module_param(max_data_size, uint, S_IRUSR | S_IWUSR);
+MODULE_PARM_DESC(max_data_size, "max read/write data size [4,8..65536] (^2)");
+
+static void hsc_add_tail(struct hsc_channel *channel, struct hsi_msg *msg,
+                                                        struct list_head *queue)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&channel->lock, flags);
+        list_add_tail(&msg->link, queue);
+        spin_unlock_irqrestore(&channel->lock, flags);
+}
+
+static struct hsi_msg *hsc_get_first_msg(struct hsc_channel *channel,
+                                                        struct list_head *queue)
+{
+        struct hsi_msg *msg = NULL;
+        unsigned long flags;
+
+        spin_lock_irqsave(&channel->lock, flags);
+
+        if (list_empty(queue))
+                goto out;
+
+        msg = list_first_entry(queue, struct hsi_msg, link);
+        list_del(&msg->link);
+out:
+        spin_unlock_irqrestore(&channel->lock, flags);
+
+        return msg;
+}
+
+static inline void hsc_msg_free(struct hsi_msg *msg)
+{
+        kfree(sg_virt(msg->sgt.sgl));
+        hsi_free_msg(msg);
+}
+
+static void hsc_free_list(struct list_head *list)
+{
+        struct hsi_msg *msg, *tmp;
+
+        list_for_each_entry_safe(msg, tmp, list, link) {
+                list_del(&msg->link);
+                hsc_msg_free(msg);
+        }
+}
+
+static void hsc_reset_list(struct hsc_channel *channel, struct list_head *l)
+{
+        unsigned long flags;
+        LIST_HEAD(list);
+
+        spin_lock_irqsave(&channel->lock, flags);
+        list_splice_init(l, &list);
+        spin_unlock_irqrestore(&channel->lock, flags);
+
+        hsc_free_list(&list);
+}
+
+static inline struct hsi_msg *hsc_msg_alloc(unsigned int alloc_size)
+{
+        struct hsi_msg *msg;
+        void *buf;
+
+        msg = hsi_alloc_msg(1, GFP_KERNEL);
+        if (!msg)
+                goto out;
+        buf = kmalloc(alloc_size, GFP_KERNEL);
+        if (!buf) {
+                hsi_free_msg(msg);
+                goto out;
+        }
+        sg_init_one(msg->sgt.sgl, buf, alloc_size);
+        /* Ignore false positive, due to sg pointer handling */
+        kmemleak_ignore(buf);
+
+        return msg;
+out:
+        return NULL;
+}
+
+static inline int hsc_msgs_alloc(struct hsc_channel *channel)
+{
+        struct hsi_msg *msg;
+        int i;
+
+        for (i = 0; i < HSC_MSGS; i++) {
+                msg = hsc_msg_alloc(max_data_size);
+                if (!msg)
+                        goto out;
+                msg->channel = channel->ch;
+                list_add_tail(&msg->link, &channel->free_msgs_list);
+        }
+
+        return 0;
+out:
+        hsc_free_list(&channel->free_msgs_list);
+
+        return -ENOMEM;
+}
+
+static inline unsigned int hsc_msg_len_get(struct hsi_msg *msg)
+{
+        return msg->sgt.sgl->length;
+}
+
+static inline void hsc_msg_len_set(struct hsi_msg *msg, unsigned int len)
+{
+        msg->sgt.sgl->length = len;
+}
+
+static void hsc_rx_completed(struct hsi_msg *msg)
+{
+        struct hsc_client_data *cl_data = hsi_client_drvdata(msg->cl);
+        struct hsc_channel *channel = cl_data->channels + msg->channel;
+
+        if (test_bit(HSC_CH_READ, &channel->flags)) {
+                hsc_add_tail(channel, msg, &channel->rx_msgs_queue);
+                wake_up(&channel->rx_wait);
+        } else {
+                hsc_add_tail(channel, msg, &channel->free_msgs_list);
+        }
+}
+
+static void hsc_rx_msg_destructor(struct hsi_msg *msg)
+{
+        msg->status = HSI_STATUS_ERROR;
+        hsc_msg_len_set(msg, 0);
+        hsc_rx_completed(msg);
+}
+
+static void hsc_tx_completed(struct hsi_msg *msg)
+{
+        struct hsc_client_data *cl_data = hsi_client_drvdata(msg->cl);
+        struct hsc_channel *channel = cl_data->channels + msg->channel;
+
+        if (test_bit(HSC_CH_WRITE, &channel->flags)) {
+                hsc_add_tail(channel, msg, &channel->tx_msgs_queue);
+                wake_up(&channel->tx_wait);
+        } else {
+                hsc_add_tail(channel, msg, &channel->free_msgs_list);
+        }
+}
+
+static void hsc_tx_msg_destructor(struct hsi_msg *msg)
+{
+        msg->status = HSI_STATUS_ERROR;
+        hsc_msg_len_set(msg, 0);
+        hsc_tx_completed(msg);
+}
+
+static void hsc_break_req_destructor(struct hsi_msg *msg)
+{
+        struct hsc_client_data *cl_data = hsi_client_drvdata(msg->cl);
+
+        hsi_free_msg(msg);
+        clear_bit(HSC_RXBREAK, &cl_data->flags);
+}
+
+static void hsc_break_received(struct hsi_msg *msg)
+{
+        struct hsc_client_data *cl_data = hsi_client_drvdata(msg->cl);
+        struct hsc_channel *channel = cl_data->channels;
+        int i, ret;
+
+        /* Broadcast HWBREAK on all channels */
+        for (i = 0; i < HSC_DEVS; i++, channel++) {
+                struct hsi_msg *msg2;
+
+                if (!test_bit(HSC_CH_READ, &channel->flags))
+                        continue;
+                msg2 = hsc_get_first_msg(channel, &channel->free_msgs_list);
+                if (!msg2)
+                        continue;
+                clear_bit(HSC_CH_READ, &channel->flags);
+                hsc_msg_len_set(msg2, 0);
+                msg2->status = HSI_STATUS_COMPLETED;
+                hsc_add_tail(channel, msg2, &channel->rx_msgs_queue);
+                wake_up(&channel->rx_wait);
+        }
+        hsi_flush(msg->cl);
+        ret = hsi_async_read(msg->cl, msg);
+        if (ret < 0)
+                hsc_break_req_destructor(msg);
+}
+
+static int hsc_break_request(struct hsi_client *cl)
+{
+        struct hsc_client_data *cl_data = hsi_client_drvdata(cl);
+        struct hsi_msg *msg;
+        int ret;
+
+        if (test_and_set_bit(HSC_RXBREAK, &cl_data->flags))
+                return -EBUSY;
+
+        msg = hsi_alloc_msg(0, GFP_KERNEL);
+        if (!msg) {
+                clear_bit(HSC_RXBREAK, &cl_data->flags);
+                return -ENOMEM;
+        }
+        msg->break_frame = 1;
+        msg->complete = hsc_break_received;
+        msg->destructor = hsc_break_req_destructor;
+        ret = hsi_async_read(cl, msg);
+        if (ret < 0)
+                hsc_break_req_destructor(msg);
+
+        return ret;
+}
+
+static int hsc_break_send(struct hsi_client *cl)
+{
+        struct hsi_msg *msg;
+        int ret;
+
+        msg = hsi_alloc_msg(0, GFP_ATOMIC);
+        if (!msg)
+                return -ENOMEM;
+        msg->break_frame = 1;
+        msg->complete = hsi_free_msg;
+        msg->destructor = hsi_free_msg;
+        ret = hsi_async_write(cl, msg);
+        if (ret < 0)
+                hsi_free_msg(msg);
+
+        return ret;
+}
+
+static int hsc_rx_set(struct hsi_client *cl, struct hsc_rx_config *rxc)
+{
+        struct hsi_config tmp;
+        int ret;
+
+        if ((rxc->mode != HSI_MODE_STREAM) && (rxc->mode != HSI_MODE_FRAME))
+                return -EINVAL;
+        if ((rxc->channels == 0) || (rxc->channels > HSC_DEVS))
+                return -EINVAL;
+        if (rxc->channels & (rxc->channels - 1))
+                return -EINVAL;
+        if ((rxc->flow != HSI_FLOW_SYNC) && (rxc->flow != HSI_FLOW_PIPE))
+                return -EINVAL;
+        tmp = cl->rx_cfg;
+        cl->rx_cfg.mode = rxc->mode;
+        cl->rx_cfg.channels = rxc->channels;
+        cl->rx_cfg.flow = rxc->flow;
+        ret = hsi_setup(cl);
+        if (ret < 0) {
+                cl->rx_cfg = tmp;
+                return ret;
+        }
+        if (rxc->mode == HSI_MODE_FRAME)
+                hsc_break_request(cl);
+
+        return ret;
+}
+
+static inline void hsc_rx_get(struct hsi_client *cl, struct hsc_rx_config *rxc)
+{
+        rxc->mode = cl->rx_cfg.mode;
+        rxc->channels = cl->rx_cfg.channels;
+        rxc->flow = cl->rx_cfg.flow;
+}
+
+static int hsc_tx_set(struct hsi_client *cl, struct hsc_tx_config *txc)
+{
+        struct hsi_config tmp;
+        int ret;
+
+        if ((txc->mode != HSI_MODE_STREAM) && (txc->mode != HSI_MODE_FRAME))
+                return -EINVAL;
+        if ((txc->channels == 0) || (txc->channels > HSC_DEVS))
+                return -EINVAL;
+        if (txc->channels & (txc->channels - 1))
+                return -EINVAL;
+        if ((txc->arb_mode != HSI_ARB_RR) && (txc->arb_mode != HSI_ARB_PRIO))
+                return -EINVAL;
+        tmp = cl->tx_cfg;
+        cl->tx_cfg.mode = txc->mode;
+        cl->tx_cfg.channels = txc->channels;
+        cl->tx_cfg.speed = txc->speed;
+        cl->tx_cfg.arb_mode = txc->arb_mode;
+        ret = hsi_setup(cl);
+        if (ret < 0) {
+                cl->tx_cfg = tmp;
+                return ret;
+        }
+
+        return ret;
+}
+
+static inline void hsc_tx_get(struct hsi_client *cl, struct hsc_tx_config *txc)
+{
+        txc->mode = cl->tx_cfg.mode;
+        txc->channels = cl->tx_cfg.channels;
+        txc->speed = cl->tx_cfg.speed;
+        txc->arb_mode = cl->tx_cfg.arb_mode;
+}
+
+static ssize_t hsc_read(struct file *file, char __user *buf, size_t len,
+                                                loff_t *ppos __maybe_unused)
+{
+        struct hsc_channel *channel = file->private_data;
+        struct hsi_msg *msg;
+        ssize_t ret;
+
+        if (len == 0)
+                return 0;
+        if (!IS_ALIGNED(len, sizeof(u32)))
+                return -EINVAL;
+        if (len > max_data_size)
+                len = max_data_size;
+        if (channel->ch >= channel->cl->rx_cfg.channels)
+                return -ECHRNG;
+        if (test_and_set_bit(HSC_CH_READ, &channel->flags))
+                return -EBUSY;
+        msg = hsc_get_first_msg(channel, &channel->free_msgs_list);
+        if (!msg) {
+                ret = -ENOSPC;
+                goto out;
+        }
+        hsc_msg_len_set(msg, len);
+        msg->complete = hsc_rx_completed;
+        msg->destructor = hsc_rx_msg_destructor;
+        ret = hsi_async_read(channel->cl, msg);
+        if (ret < 0) {
+                hsc_add_tail(channel, msg, &channel->free_msgs_list);
+                goto out;
+        }
+
+        ret = wait_event_interruptible(channel->rx_wait,
+                                        !list_empty(&channel->rx_msgs_queue));
+        if (ret < 0) {
+                clear_bit(HSC_CH_READ, &channel->flags);
+                hsi_flush(channel->cl);
+                return -EINTR;
+        }
+
+        msg = hsc_get_first_msg(channel, &channel->rx_msgs_queue);
+        if (msg) {
+                if (msg->status != HSI_STATUS_ERROR) {
+                        ret = copy_to_user((void __user *)buf,
+                        sg_virt(msg->sgt.sgl), hsc_msg_len_get(msg));
+                        if (ret)
+                                ret = -EFAULT;
+                        else
+                                ret = hsc_msg_len_get(msg);
+                } else {
+                        ret = -EIO;
+                }
+                hsc_add_tail(channel, msg, &channel->free_msgs_list);
+        }
+out:
+        clear_bit(HSC_CH_READ, &channel->flags);
+
+        return ret;
+}
+
+static ssize_t hsc_write(struct file *file, const char __user *buf, size_t len,
+                                                loff_t *ppos __maybe_unused)
+{
+        struct hsc_channel *channel = file->private_data;
+        struct hsi_msg *msg;
+        ssize_t ret;
+
+        if ((len == 0) || !IS_ALIGNED(len, sizeof(u32)))
+                return -EINVAL;
+        if (len > max_data_size)
+                len = max_data_size;
+        if (channel->ch >= channel->cl->tx_cfg.channels)
+                return -ECHRNG;
+        if (test_and_set_bit(HSC_CH_WRITE, &channel->flags))
+                return -EBUSY;
+        msg = hsc_get_first_msg(channel, &channel->free_msgs_list);
+        if (!msg) {
+                clear_bit(HSC_CH_WRITE, &channel->flags);
+                return -ENOSPC;
+        }
+        if (copy_from_user(sg_virt(msg->sgt.sgl), (void __user *)buf, len)) {
+                ret = -EFAULT;
+                goto out;
+        }
+        hsc_msg_len_set(msg, len);
+        msg->complete = hsc_tx_completed;
+        msg->destructor = hsc_tx_msg_destructor;
+        ret = hsi_async_write(channel->cl, msg);
+        if (ret < 0)
+                goto out;
+
+        ret = wait_event_interruptible(channel->tx_wait,
+                                        !list_empty(&channel->tx_msgs_queue));
+        if (ret < 0) {
+                clear_bit(HSC_CH_WRITE, &channel->flags);
+                hsi_flush(channel->cl);
+                return -EINTR;
+        }
+
+        msg = hsc_get_first_msg(channel, &channel->tx_msgs_queue);
+        if (msg) {
+                if (msg->status == HSI_STATUS_ERROR)
+                        ret = -EIO;
+                else
+                        ret = hsc_msg_len_get(msg);
+
+                hsc_add_tail(channel, msg, &channel->free_msgs_list);
+        }
+out:
+        clear_bit(HSC_CH_WRITE, &channel->flags);
+
+        return ret;
+}
+
+static long hsc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        struct hsc_channel *channel = file->private_data;
+        unsigned int state;
+        struct hsc_rx_config rxc;
+        struct hsc_tx_config txc;
+        long ret = 0;
+
+        switch (cmd) {
+        case HSC_RESET:
+                hsi_flush(channel->cl);
+                break;
+        case HSC_SET_PM:
+                if (copy_from_user(&state, (void __user *)arg, sizeof(state)))
+                        return -EFAULT;
+                if (state == HSC_PM_DISABLE) {
+                        if (test_and_set_bit(HSC_CH_WLINE, &channel->flags))
+                                return -EINVAL;
+                        ret = hsi_start_tx(channel->cl);
+                } else if (state == HSC_PM_ENABLE) {
+                        if (!test_and_clear_bit(HSC_CH_WLINE, &channel->flags))
+                                return -EINVAL;
+                        ret = hsi_stop_tx(channel->cl);
+                } else {
+                        ret = -EINVAL;
+                }
+                break;
+        case HSC_SEND_BREAK:
+                return hsc_break_send(channel->cl);
+        case HSC_SET_RX:
+                if (copy_from_user(&rxc, (void __user *)arg, sizeof(rxc)))
+                        return -EFAULT;
+                return hsc_rx_set(channel->cl, &rxc);
+        case HSC_GET_RX:
+                hsc_rx_get(channel->cl, &rxc);
+                if (copy_to_user((void __user *)arg, &rxc, sizeof(rxc)))
+                        return -EFAULT;
+                break;
+        case HSC_SET_TX:
+                if (copy_from_user(&txc, (void __user *)arg, sizeof(txc)))
+                        return -EFAULT;
+                return hsc_tx_set(channel->cl, &txc);
+        case HSC_GET_TX:
+                hsc_tx_get(channel->cl, &txc);
+                if (copy_to_user((void __user *)arg, &txc, sizeof(txc)))
+                        return -EFAULT;
+                break;
+        default:
+                return -ENOIOCTLCMD;
+        }
+
+        return ret;
+}
+
+static inline void __hsc_port_release(struct hsc_client_data *cl_data)
+{
+        BUG_ON(cl_data->usecnt == 0);
+
+        if (--cl_data->usecnt == 0) {
+                hsi_flush(cl_data->cl);
+                hsi_release_port(cl_data->cl);
+        }
+}
+
+static int hsc_open(struct inode *inode, struct file *file)
+{
+        struct hsc_client_data *cl_data;
+        struct hsc_channel *channel;
+        int ret = 0;
+
+        pr_debug("open, minor = %d\n", iminor(inode));
+
+        cl_data = container_of(inode->i_cdev, struct hsc_client_data, cdev);
+        mutex_lock(&cl_data->lock);
+        channel = cl_data->channels + (iminor(inode) & HSC_CH_MASK);
+
+        if (test_and_set_bit(HSC_CH_OPEN, &channel->flags)) {
+                ret = -EBUSY;
+                goto out;
+        }
+        /*
+         * Check if we have already claimed the port associated to the HSI
+         * client. If not then try to claim it, else increase its refcount
+         */
+        if (cl_data->usecnt == 0) {
+                ret = hsi_claim_port(cl_data->cl, 0);
+                if (ret < 0)
+                        goto out;
+                hsi_setup(cl_data->cl);
+        }
+        cl_data->usecnt++;
+
+        ret = hsc_msgs_alloc(channel);
+        if (ret < 0) {
+                __hsc_port_release(cl_data);
+                goto out;
+        }
+
+        file->private_data = channel;
+        mutex_unlock(&cl_data->lock);
+
+        return ret;
+out:
+        mutex_unlock(&cl_data->lock);
+
+        return ret;
+}
+
+static int hsc_release(struct inode *inode __maybe_unused, struct file *file)
+{
+        struct hsc_channel *channel = file->private_data;
+        struct hsc_client_data *cl_data = channel->cl_data;
+
+        mutex_lock(&cl_data->lock);
+        file->private_data = NULL;
+        if (test_and_clear_bit(HSC_CH_WLINE, &channel->flags))
+                hsi_stop_tx(channel->cl);
+        __hsc_port_release(cl_data);
+        hsc_reset_list(channel, &channel->rx_msgs_queue);
+        hsc_reset_list(channel, &channel->tx_msgs_queue);
+        hsc_reset_list(channel, &channel->free_msgs_list);
+        clear_bit(HSC_CH_READ, &channel->flags);
+        clear_bit(HSC_CH_WRITE, &channel->flags);
+        clear_bit(HSC_CH_OPEN, &channel->flags);
+        wake_up(&channel->rx_wait);
+        wake_up(&channel->tx_wait);
+        mutex_unlock(&cl_data->lock);
+
+        return 0;
+}
+
+static const struct file_operations hsc_fops = {
+        .owner          = THIS_MODULE,
+        .read           = hsc_read,
+        .write          = hsc_write,
+        .unlocked_ioctl = hsc_ioctl,
+        .open           = hsc_open,
+        .release        = hsc_release,
+};
+
+static void __devinit hsc_channel_init(struct hsc_channel *channel)
+{
+        init_waitqueue_head(&channel->rx_wait);
+        init_waitqueue_head(&channel->tx_wait);
+        spin_lock_init(&channel->lock);
+        INIT_LIST_HEAD(&channel->free_msgs_list);
+        INIT_LIST_HEAD(&channel->rx_msgs_queue);
+        INIT_LIST_HEAD(&channel->tx_msgs_queue);
+}
+
+static int __devinit hsc_probe(struct device *dev)
+{
+        const char devname[] = "hsi_char";
+        struct hsc_client_data *cl_data;
+        struct hsc_channel *channel;
+        struct hsi_client *cl = to_hsi_client(dev);
+        unsigned int hsc_baseminor;
+        dev_t hsc_dev;
+        int ret;
+        int i;
+
+        cl_data = kzalloc(sizeof(*cl_data), GFP_KERNEL);
+        if (!cl_data) {
+                dev_err(dev, "Could not allocate hsc_client_data\n");
+                return -ENOMEM;
+        }
+        hsc_baseminor = HSC_BASEMINOR(hsi_id(cl), hsi_port_id(cl));
+        if (!hsc_major) {
+                ret = alloc_chrdev_region(&hsc_dev, hsc_baseminor,
+                                                HSC_DEVS, devname);
+                if (ret > 0)
+                        hsc_major = MAJOR(hsc_dev);
+        } else {
+                hsc_dev = MKDEV(hsc_major, hsc_baseminor);
+                ret = register_chrdev_region(hsc_dev, HSC_DEVS, devname);
+        }
+        if (ret < 0) {
+                dev_err(dev, "Device %s allocation failed %d\n",
+                                        hsc_major ? "minor" : "major", ret);
+                goto out1;
+        }
+        mutex_init(&cl_data->lock);
+        hsi_client_set_drvdata(cl, cl_data);
+        cdev_init(&cl_data->cdev, &hsc_fops);
+        cl_data->cdev.owner = THIS_MODULE;
+        cl_data->cl = cl;
+        for (i = 0, channel = cl_data->channels; i < HSC_DEVS; i++, channel++) {
+                hsc_channel_init(channel);
+                channel->ch = i;
+                channel->cl = cl;
+                channel->cl_data = cl_data;
+        }
+
+        /* 1 hsi client -> N char devices (one for each channel) */
+        ret = cdev_add(&cl_data->cdev, hsc_dev, HSC_DEVS);
+        if (ret) {
+                dev_err(dev, "Could not add char device %d\n", ret);
+                goto out2;
+        }
+
+        return 0;
+out2:
+        unregister_chrdev_region(hsc_dev, HSC_DEVS);
+out1:
+        kfree(cl_data);
+
+        return ret;
+}
+
+static int __devexit hsc_remove(struct device *dev)
+{
+        struct hsi_client *cl = to_hsi_client(dev);
+        struct hsc_client_data *cl_data = hsi_client_drvdata(cl);
+        dev_t hsc_dev = cl_data->cdev.dev;
+
+        cdev_del(&cl_data->cdev);
+        unregister_chrdev_region(hsc_dev, HSC_DEVS);
+        hsi_client_set_drvdata(cl, NULL);
+        kfree(cl_data);
+
+        return 0;
+}
+
+static struct hsi_client_driver hsc_driver = {
+        .driver = {
+                .name   = "hsi_char",
+                .owner  = THIS_MODULE,
+                .probe  = hsc_probe,
+                .remove = __devexit_p(hsc_remove),
+        },
+};
+
+static int __init hsc_init(void)
+{
+        int ret;
+
+        if ((max_data_size < 4) || (max_data_size > 0x10000) ||
+                (max_data_size & (max_data_size - 1))) {
+                pr_err("Invalid max read/write data size");
+                return -EINVAL;
+        }
+
+        ret = hsi_register_client_driver(&hsc_driver);
+        if (ret) {
+                pr_err("Error while registering HSI/SSI driver %d", ret);
+                return ret;
+        }
+
+        pr_info("HSI/SSI char device loaded\n");
+
+        return 0;
+}
+module_init(hsc_init);
+
+static void __exit hsc_exit(void)
+{
+        hsi_unregister_client_driver(&hsc_driver);
+        pr_info("HSI char device removed\n");
+}
+module_exit(hsc_exit);
+
+MODULE_AUTHOR("Andras Domokos <andras.domokos@nokia.com>");
+MODULE_ALIAS("hsi:hsi_char");
+MODULE_DESCRIPTION("HSI character device");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/hsi/hsi_char.h b/include/linux/hsi/hsi_char.h
new file mode 100644
index 000000000000..76160b4f455d
--- /dev/null
+++ b/include/linux/hsi/hsi_char.h
@@ -0,0 +1,63 @@
+/*
+ * Part of the HSI character device driver.
+ *
+ * Copyright (C) 2010 Nokia Corporation. All rights reserved.
+ *
+ * Contact: Andras Domokos <andras.domokos at nokia.com>
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+
+#ifndef __HSI_CHAR_H
+#define __HSI_CHAR_H
+
+#define HSI_CHAR_MAGIC          'k'
+#define HSC_IOW(num, dtype)     _IOW(HSI_CHAR_MAGIC, num, dtype)
+#define HSC_IOR(num, dtype)     _IOR(HSI_CHAR_MAGIC, num, dtype)
+#define HSC_IOWR(num, dtype)    _IOWR(HSI_CHAR_MAGIC, num, dtype)
+#define HSC_IO(num)             _IO(HSI_CHAR_MAGIC, num)
+
+#define HSC_RESET               HSC_IO(16)
+#define HSC_SET_PM              HSC_IO(17)
+#define HSC_SEND_BREAK          HSC_IO(18)
+#define HSC_SET_RX              HSC_IOW(19, struct hsc_rx_config)
+#define HSC_GET_RX              HSC_IOW(20, struct hsc_rx_config)
+#define HSC_SET_TX              HSC_IOW(21, struct hsc_tx_config)
+#define HSC_GET_TX              HSC_IOW(22, struct hsc_tx_config)
+
+#define HSC_PM_DISABLE          0
+#define HSC_PM_ENABLE           1
+
+#define HSC_MODE_STREAM         1
+#define HSC_MODE_FRAME          2
+#define HSC_FLOW_SYNC           0
+#define HSC_ARB_RR              0
+#define HSC_ARB_PRIO            1
+
+struct hsc_rx_config {
+        uint32_t mode;
+        uint32_t flow;
+        uint32_t channels;
+};
+
+struct hsc_tx_config {
+        uint32_t mode;
+        uint32_t channels;
+        uint32_t speed;
+        uint32_t arb_mode;
+};
+
+#endif /* __HSI_CHAR_H */