Staging: poch: Rx control register init

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / drivers / char / hvc_iucv.c

/*
 * hvc_iucv.c - z/VM IUCV back-end for the Hypervisor Console (HVC)
 *
 * This back-end for HVC provides terminal access via
 * z/VM IUCV communication paths.
 *
 * Copyright IBM Corp. 2008.
 *
 * Author(s):   Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
 */
#define KMSG_COMPONENT          "hvc_iucv"

#include <linux/types.h>
#include <asm/ebcdic.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <net/iucv/iucv.h>

#include "hvc_console.h"


/* HVC backend for z/VM IUCV */
#define HVC_IUCV_MAGIC          0xc9e4c3e5
#define MAX_HVC_IUCV_LINES      HVC_ALLOC_TTY_ADAPTERS
#define MEMPOOL_MIN_NR          (PAGE_SIZE / sizeof(struct iucv_tty_buffer)/4)

/* IUCV TTY message  */
#define MSG_VERSION             0x02    /* Message version */
#define MSG_TYPE_ERROR          0x01    /* Error message */
#define MSG_TYPE_TERMENV        0x02    /* Terminal environment variable */
#define MSG_TYPE_TERMIOS        0x04    /* Terminal IO struct update */
#define MSG_TYPE_WINSIZE        0x08    /* Terminal window size update */
#define MSG_TYPE_DATA           0x10    /* Terminal data */

#define MSG_SIZE(s)             ((s) + offsetof(struct iucv_tty_msg, data))
struct iucv_tty_msg {
        u8      version;                /* Message version */
        u8      type;                   /* Message type */
#define MSG_MAX_DATALEN         (~(u16)0)
        u16     datalen;                /* Payload length */
        u8      data[];                 /* Payload buffer */
} __attribute__((packed));

enum iucv_state_t {
        IUCV_DISCONN    = 0,
        IUCV_CONNECTED  = 1,
        IUCV_SEVERED    = 2,
};

enum tty_state_t {
        TTY_CLOSED      = 0,
        TTY_OPENED      = 1,
};

struct hvc_iucv_private {
        struct hvc_struct       *hvc; /* HVC console struct reference */
        u8                      srv_name[8];    /* IUCV service name (ebcdic) */
        enum iucv_state_t       iucv_state;     /* IUCV connection status */
        enum tty_state_t        tty_state;      /* TTY status */
        struct iucv_path        *path;          /* IUCV path pointer */
        spinlock_t              lock;           /* hvc_iucv_private lock */
        struct list_head        tty_outqueue;   /* outgoing IUCV messages */
        struct list_head        tty_inqueue;    /* incoming IUCV messages */
};

struct iucv_tty_buffer {
        struct list_head        list;   /* list pointer */
        struct iucv_message     msg;    /* store an incoming IUCV message */
        size_t                  offset; /* data buffer offset */
        struct iucv_tty_msg     *mbuf;  /* buffer to store input/output data */
};

/* IUCV callback handler */
static  int hvc_iucv_path_pending(struct iucv_path *, u8[8], u8[16]);
static void hvc_iucv_path_severed(struct iucv_path *, u8[16]);
static void hvc_iucv_msg_pending(struct iucv_path *, struct iucv_message *);
static void hvc_iucv_msg_complete(struct iucv_path *, struct iucv_message *);


/* Kernel module parameters */
static unsigned long hvc_iucv_devices;

/* Array of allocated hvc iucv tty lines... */
static struct hvc_iucv_private *hvc_iucv_table[MAX_HVC_IUCV_LINES];

/* Kmem cache and mempool for iucv_tty_buffer elements */
static struct kmem_cache *hvc_iucv_buffer_cache;
static mempool_t *hvc_iucv_mempool;

/* IUCV handler callback functions */
static struct iucv_handler hvc_iucv_handler = {
        .path_pending  = hvc_iucv_path_pending,
        .path_severed  = hvc_iucv_path_severed,
        .message_complete = hvc_iucv_msg_complete,
        .message_pending  = hvc_iucv_msg_pending,
};


/**
 * hvc_iucv_get_private() - Return a struct hvc_iucv_private instance.
 * @num:        The HVC virtual terminal number (vtermno)
 *
 * This function returns the struct hvc_iucv_private instance that corresponds
 * to the HVC virtual terminal number specified as parameter @num.
 */
struct hvc_iucv_private *hvc_iucv_get_private(uint32_t num)
{
        if ((num < HVC_IUCV_MAGIC) || (num - HVC_IUCV_MAGIC > hvc_iucv_devices))
                return NULL;
        return hvc_iucv_table[num - HVC_IUCV_MAGIC];
}

/**
 * alloc_tty_buffer() - Returns a new struct iucv_tty_buffer element.
 * @size:       Size of the internal buffer used to store data.
 * @flags:      Memory allocation flags passed to mempool.
 *
 * This function allocates a new struct iucv_tty_buffer element and, optionally,
 * allocates an internal data buffer with the specified size @size.
 * Note: The total message size arises from the internal buffer size and the
 *       members of the iucv_tty_msg structure.
 *
 * The function returns NULL if memory allocation has failed.
 */
static struct iucv_tty_buffer *alloc_tty_buffer(size_t size, gfp_t flags)
{
        struct iucv_tty_buffer *bufp;

        bufp = mempool_alloc(hvc_iucv_mempool, flags);
        if (!bufp)
                return NULL;
        memset(bufp, 0, sizeof(struct iucv_tty_buffer));

        if (size > 0) {
                bufp->msg.length = MSG_SIZE(size);
                bufp->mbuf = kmalloc(bufp->msg.length, flags);
                if (!bufp->mbuf) {
                        mempool_free(bufp, hvc_iucv_mempool);
                        return NULL;
                }
                bufp->mbuf->version = MSG_VERSION;
                bufp->mbuf->type    = MSG_TYPE_DATA;
                bufp->mbuf->datalen = (u16) size;
        }
        return bufp;
}

/**
 * destroy_tty_buffer() - destroy struct iucv_tty_buffer element.
 * @bufp:       Pointer to a struct iucv_tty_buffer element, SHALL NOT be NULL.
 *
 * The destroy_tty_buffer() function frees the internal data buffer and returns
 * the struct iucv_tty_buffer element back to the mempool for freeing.
 */
static void destroy_tty_buffer(struct iucv_tty_buffer *bufp)
{
        kfree(bufp->mbuf);
        mempool_free(bufp, hvc_iucv_mempool);
}

/**
 * destroy_tty_buffer_list() - call destroy_tty_buffer() for each list element.
 * @list:       List head pointer to a list containing struct iucv_tty_buffer
 *              elements.
 *
 * Calls destroy_tty_buffer() for each struct iucv_tty_buffer element in the
 * list @list.
 */
static void destroy_tty_buffer_list(struct list_head *list)
{
        struct iucv_tty_buffer *ent, *next;

        list_for_each_entry_safe(ent, next, list, list) {
                list_del(&ent->list);
                destroy_tty_buffer(ent);
        }
}

/**
 * hvc_iucv_write() - Receive IUCV message write data to HVC console buffer.
 * @priv:               Pointer to hvc_iucv_private structure.
 * @buf:                HVC console buffer for writing received terminal data.
 * @count:              HVC console buffer size.
 * @has_more_data:      Pointer to an int variable.
 *
 * The function picks up pending messages from the input queue and receives
 * the message data that is then written to the specified buffer @buf.
 * If the buffer size @count is less than the data message size, then the
 * message is kept on the input queue and @has_more_data is set to 1.
 * If the message data has been entirely written, the message is removed from
 * the input queue.
 *
 * The function returns the number of bytes written to the terminal, zero if
 * there are no pending data messages available or if there is no established
 * IUCV path.
 * If the IUCV path has been severed, then -EPIPE is returned to cause a
 * hang up (that is issued by the HVC console layer).
 */
static int hvc_iucv_write(struct hvc_iucv_private *priv,
                          char *buf, int count, int *has_more_data)
{
        struct iucv_tty_buffer *rb;
        int written;
        int rc;

        /* Immediately return if there is no IUCV connection */
        if (priv->iucv_state == IUCV_DISCONN)
                return 0;

        /* If the IUCV path has been severed, return -EPIPE to inform the
         * hvc console layer to hang up the tty device. */
        if (priv->iucv_state == IUCV_SEVERED)
                return -EPIPE;

        /* check if there are pending messages */
        if (list_empty(&priv->tty_inqueue))
                return 0;

        /* receive a iucv message and flip data to the tty (ldisc) */
        rb = list_first_entry(&priv->tty_inqueue, struct iucv_tty_buffer, list);

        written = 0;
        if (!rb->mbuf) { /* message not yet received ... */
                /* allocate mem to store msg data; if no memory is available
                 * then leave the buffer on the list and re-try later */
                rb->mbuf = kmalloc(rb->msg.length, GFP_ATOMIC);
                if (!rb->mbuf)
                        return -ENOMEM;

                rc = __iucv_message_receive(priv->path, &rb->msg, 0,
                                            rb->mbuf, rb->msg.length, NULL);
                switch (rc) {
                case 0: /* Successful       */
                        break;
                case 2: /* No message found */
                case 9: /* Message purged   */
                        break;
                default:
                        written = -EIO;
                }
                /* remove buffer if an error has occured or received data
                 * is not correct */
                if (rc || (rb->mbuf->version != MSG_VERSION) ||
                          (rb->msg.length    != MSG_SIZE(rb->mbuf->datalen)))
                        goto out_remove_buffer;
        }

        switch (rb->mbuf->type) {
        case MSG_TYPE_DATA:
                written = min_t(int, rb->mbuf->datalen - rb->offset, count);
                memcpy(buf, rb->mbuf->data + rb->offset, written);
                if (written < (rb->mbuf->datalen - rb->offset)) {
                        rb->offset += written;
                        *has_more_data = 1;
                        goto out_written;
                }
                break;

        case MSG_TYPE_WINSIZE:
                if (rb->mbuf->datalen != sizeof(struct winsize))
                        break;
                hvc_resize(priv->hvc, *((struct winsize *)rb->mbuf->data));
                break;

        case MSG_TYPE_ERROR:    /* ignored ... */
        case MSG_TYPE_TERMENV:  /* ignored ... */
        case MSG_TYPE_TERMIOS:  /* ignored ... */
                break;
        }

out_remove_buffer:
        list_del(&rb->list);
        destroy_tty_buffer(rb);
        *has_more_data = !list_empty(&priv->tty_inqueue);

out_written:
        return written;
}

/**
 * hvc_iucv_get_chars() - HVC get_chars operation.
 * @vtermno:    HVC virtual terminal number.
 * @buf:        Pointer to a buffer to store data
 * @count:      Size of buffer available for writing
 *
 * The hvc_console thread calls this method to read characters from
 * the terminal backend. If an IUCV communication path has been established,
 * pending IUCV messages are received and data is copied into buffer @buf
 * up to @count bytes.
 *
 * Locking:     The routine gets called under an irqsave() spinlock; and
 *              the routine locks the struct hvc_iucv_private->lock to call
 *              helper functions.
 */
static int hvc_iucv_get_chars(uint32_t vtermno, char *buf, int count)
{
        struct hvc_iucv_private *priv = hvc_iucv_get_private(vtermno);
        int written;
        int has_more_data;

        if (count <= 0)
                return 0;

        if (!priv)
                return -ENODEV;

        spin_lock(&priv->lock);
        has_more_data = 0;
        written = hvc_iucv_write(priv, buf, count, &has_more_data);
        spin_unlock(&priv->lock);

        /* if there are still messages on the queue... schedule another run */
        if (has_more_data)
                hvc_kick();

        return written;
}

/**
 * hvc_iucv_send() - Send an IUCV message containing terminal data.
 * @priv:       Pointer to struct hvc_iucv_private instance.
 * @buf:        Buffer containing data to send.
 * @size:       Size of buffer and amount of data to send.
 *
 * If an IUCV communication path is established, the function copies the buffer
 * data to a newly allocated struct iucv_tty_buffer element, sends the data and
 * puts the element to the outqueue.
 *
 * If there is no IUCV communication path established, the function returns 0.
 * If an existing IUCV communicaton path has been severed, the function returns
 * -EPIPE (can be passed to HVC layer to cause a tty hangup).
 */
static int hvc_iucv_send(struct hvc_iucv_private *priv, const char *buf,
                         int count)
{
        struct iucv_tty_buffer *sb;
        int rc;
        u16 len;

        if (priv->iucv_state == IUCV_SEVERED)
                return -EPIPE;

        if (priv->iucv_state == IUCV_DISCONN)
                return 0;

        len = min_t(u16, MSG_MAX_DATALEN, count);

        /* allocate internal buffer to store msg data and also compute total
         * message length */
        sb = alloc_tty_buffer(len, GFP_ATOMIC);
        if (!sb)
                return -ENOMEM;

        sb->mbuf->datalen = len;
        memcpy(sb->mbuf->data, buf, len);

        list_add_tail(&sb->list, &priv->tty_outqueue);

        rc = __iucv_message_send(priv->path, &sb->msg, 0, 0,
                                 (void *) sb->mbuf, sb->msg.length);
        if (rc) {
                list_del(&sb->list);
                destroy_tty_buffer(sb);
                len = 0;
        }

        return len;
}

/**
 * hvc_iucv_put_chars() - HVC put_chars operation.
 * @vtermno:    HVC virtual terminal number.
 * @buf:        Pointer to an buffer to read data from
 * @count:      Size of buffer available for reading
 *
 * The hvc_console thread calls this method to write characters from
 * to the terminal backend.
 * The function calls hvc_iucv_send() under the lock of the
 * struct hvc_iucv_private instance that corresponds to the tty @vtermno.
 *
 * Locking:     The method gets called under an irqsave() spinlock; and
 *              locks struct hvc_iucv_private->lock.
 */
static int hvc_iucv_put_chars(uint32_t vtermno, const char *buf, int count)
{
        struct hvc_iucv_private *priv = hvc_iucv_get_private(vtermno);
        int sent;

        if (count <= 0)
                return 0;

        if (!priv)
                return -ENODEV;

        spin_lock(&priv->lock);
        sent = hvc_iucv_send(priv, buf, count);
        spin_unlock(&priv->lock);

        return sent;
}

/**
 * hvc_iucv_notifier_add() - HVC notifier for opening a TTY for the first time.
 * @hp: Pointer to the HVC device (struct hvc_struct)
 * @id: Additional data (originally passed to hvc_alloc): the index of an struct
 *      hvc_iucv_private instance.
 *
 * The function sets the tty state to TTY_OPEN for the struct hvc_iucv_private
 * instance that is derived from @id. Always returns 0.
 *
 * Locking:     struct hvc_iucv_private->lock, spin_lock_bh
 */
static int hvc_iucv_notifier_add(struct hvc_struct *hp, int id)
{
        struct hvc_iucv_private *priv;

        priv = hvc_iucv_get_private(id);
        if (!priv)
                return 0;

        spin_lock_bh(&priv->lock);
        priv->tty_state = TTY_OPENED;
        spin_unlock_bh(&priv->lock);

        return 0;
}

/**
 * hvc_iucv_cleanup() - Clean up function if the tty portion is finally closed.
 * @priv:       Pointer to the struct hvc_iucv_private instance.
 *
 * The functions severs the established IUCV communication path (if any), and
 * destroy struct iucv_tty_buffer elements from the in- and outqueue. Finally,
 * the functions resets the states to TTY_CLOSED and IUCV_DISCONN.
 */
static void hvc_iucv_cleanup(struct hvc_iucv_private *priv)
{
        destroy_tty_buffer_list(&priv->tty_outqueue);
        destroy_tty_buffer_list(&priv->tty_inqueue);

        priv->tty_state = TTY_CLOSED;
        priv->iucv_state = IUCV_DISCONN;
}

/**
 * hvc_iucv_notifier_hangup() - HVC notifier for tty hangups.
 * @hp: Pointer to the HVC device (struct hvc_struct)
 * @id: Additional data (originally passed to hvc_alloc): the index of an struct
 *      hvc_iucv_private instance.
 *
 * This routine notifies the HVC backend that a tty hangup (carrier loss,
 * virtual or otherwise) has occured.
 *
 * The HVC backend for z/VM IUCV ignores virtual hangups (vhangup()), to keep
 * an existing IUCV communication path established.
 * (Background: vhangup() is called from user space (by getty or login) to
 *              disable writing to the tty by other applications).
 *
 * If the tty has been opened (e.g. getty) and an established IUCV path has been
 * severed (we caused the tty hangup in that case), then the functions invokes
 * hvc_iucv_cleanup() to clean up.
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static void hvc_iucv_notifier_hangup(struct hvc_struct *hp, int id)
{
        struct hvc_iucv_private *priv;

        priv = hvc_iucv_get_private(id);
        if (!priv)
                return;

        spin_lock_bh(&priv->lock);
        /* NOTE: If the hangup was scheduled by ourself (from the iucv
         *       path_servered callback [IUCV_SEVERED]), then we have to
         *       finally clean up the tty backend structure and set state to
         *       TTY_CLOSED.
         *
         *       If the tty was hung up otherwise (e.g. vhangup()), then we
         *       ignore this hangup and keep an established IUCV path open...
         *       (...the reason is that we are not able to connect back to the
         *       client if we disconnect on hang up) */
        priv->tty_state = TTY_CLOSED;

        if (priv->iucv_state == IUCV_SEVERED)
                hvc_iucv_cleanup(priv);
        spin_unlock_bh(&priv->lock);
}

/**
 * hvc_iucv_notifier_del() - HVC notifier for closing a TTY for the last time.
 * @hp:         Pointer to the HVC device (struct hvc_struct)
 * @id:         Additional data (originally passed to hvc_alloc):
 *              the index of an struct hvc_iucv_private instance.
 *
 * This routine notifies the HVC backend that the last tty device file
 * descriptor has been closed.
 * The function calls hvc_iucv_cleanup() to clean up the struct hvc_iucv_private
 * instance.
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static void hvc_iucv_notifier_del(struct hvc_struct *hp, int id)
{
        struct hvc_iucv_private *priv;
        struct iucv_path        *path;

        priv = hvc_iucv_get_private(id);
        if (!priv)
                return;

        spin_lock_bh(&priv->lock);
        path = priv->path;              /* save reference to IUCV path */
        priv->path = NULL;
        hvc_iucv_cleanup(priv);
        spin_unlock_bh(&priv->lock);

        /* sever IUCV path outside of priv->lock due to lock ordering of:
         * priv->lock <--> iucv_table_lock */
        if (path) {
                iucv_path_sever(path, NULL);
                iucv_path_free(path);
        }
}

/**
 * hvc_iucv_path_pending() - IUCV handler to process a connection request.
 * @path:       Pending path (struct iucv_path)
 * @ipvmid:     Originator z/VM system identifier
 * @ipuser:     User specified data for this path
 *              (AF_IUCV: port/service name and originator port)
 *
 * The function uses the @ipuser data to check to determine if the pending
 * path belongs to a terminal managed by this HVC backend.
 * If the check is successful, then an additional check is done to ensure
 * that a terminal cannot be accessed multiple times (only one connection
 * to a terminal is allowed). In that particular case, the pending path is
 * severed. If it is the first connection, the pending path is accepted and
 * associated to the struct hvc_iucv_private. The iucv state is updated to
 * reflect that a communication path has been established.
 *
 * Returns 0 if the path belongs to a terminal managed by the this HVC backend;
 * otherwise returns -ENODEV in order to dispatch this path to other handlers.
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static  int hvc_iucv_path_pending(struct iucv_path *path,
                                  u8 ipvmid[8], u8 ipuser[16])
{
        struct hvc_iucv_private *priv;
        u8 nuser_data[16];
        int i, rc;

        priv = NULL;
        for (i = 0; i < hvc_iucv_devices; i++)
                if (hvc_iucv_table[i] &&
                    (0 == memcmp(hvc_iucv_table[i]->srv_name, ipuser, 8))) {
                        priv = hvc_iucv_table[i];
                        break;
                }

        if (!priv)
                return -ENODEV;

        spin_lock(&priv->lock);

        /* If the terminal is already connected or being severed, then sever
         * this path to enforce that there is only ONE established communication
         * path per terminal. */
        if (priv->iucv_state != IUCV_DISCONN) {
                iucv_path_sever(path, ipuser);
                iucv_path_free(path);
                goto out_path_handled;
        }

        /* accept path */
        memcpy(nuser_data, ipuser + 8, 8);  /* remote service (for af_iucv) */
        memcpy(nuser_data + 8, ipuser, 8);  /* local service  (for af_iucv) */
        path->msglim = 0xffff;              /* IUCV MSGLIMIT */
        path->flags &= ~IUCV_IPRMDATA;      /* TODO: use IUCV_IPRMDATA */
        rc = iucv_path_accept(path, &hvc_iucv_handler, nuser_data, priv);
        if (rc) {
                iucv_path_sever(path, ipuser);
                iucv_path_free(path);
                goto out_path_handled;
        }
        priv->path = path;
        priv->iucv_state = IUCV_CONNECTED;

out_path_handled:
        spin_unlock(&priv->lock);
        return 0;
}

/**
 * hvc_iucv_path_severed() - IUCV handler to process a path sever.
 * @path:       Pending path (struct iucv_path)
 * @ipuser:     User specified data for this path
 *              (AF_IUCV: port/service name and originator port)
 *
 * The function also severs the path (as required by the IUCV protocol) and
 * sets the iucv state to IUCV_SEVERED for the associated struct
 * hvc_iucv_private instance. Later, the IUCV_SEVERED state triggers a tty
 * hangup (hvc_iucv_get_chars() / hvc_iucv_write()).
 *
 * If tty portion of the HVC is closed then clean up the outqueue in addition.
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static void hvc_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
{
        struct hvc_iucv_private *priv = path->private;

        spin_lock(&priv->lock);
        priv->iucv_state = IUCV_SEVERED;

        /* NOTE: If the tty has not yet been opened by a getty program
         *       (e.g. to see console messages), then cleanup the
         *       hvc_iucv_private structure to allow re-connects.
         *
         *       If the tty has been opened, the get_chars() callback returns
         *       -EPIPE to signal the hvc console layer to hang up the tty. */
        priv->path = NULL;
        if (priv->tty_state == TTY_CLOSED)
                hvc_iucv_cleanup(priv);
        spin_unlock(&priv->lock);

        /* finally sever path (outside of priv->lock due to lock ordering) */
        iucv_path_sever(path, ipuser);
        iucv_path_free(path);
}

/**
 * hvc_iucv_msg_pending() - IUCV handler to process an incoming IUCV message.
 * @path:       Pending path (struct iucv_path)
 * @msg:        Pointer to the IUCV message
 *
 * The function stores an incoming message on the input queue for later
 * processing (by hvc_iucv_get_chars() / hvc_iucv_write()).
 * However, if the tty has not yet been opened, the message is rejected.
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static void hvc_iucv_msg_pending(struct iucv_path *path,
                                 struct iucv_message *msg)
{
        struct hvc_iucv_private *priv = path->private;
        struct iucv_tty_buffer *rb;

        spin_lock(&priv->lock);

        /* reject messages if tty has not yet been opened */
        if (priv->tty_state == TTY_CLOSED) {
                iucv_message_reject(path, msg);
                goto unlock_return;
        }

        /* allocate buffer an empty buffer element */
        rb = alloc_tty_buffer(0, GFP_ATOMIC);
        if (!rb) {
                iucv_message_reject(path, msg);
                goto unlock_return;     /* -ENOMEM */
        }
        rb->msg = *msg;

        list_add_tail(&rb->list, &priv->tty_inqueue);

        hvc_kick();     /* wakup hvc console thread */

unlock_return:
        spin_unlock(&priv->lock);
}

/**
 * hvc_iucv_msg_complete() - IUCV handler to process message completion
 * @path:       Pending path (struct iucv_path)
 * @msg:        Pointer to the IUCV message
 *
 * The function is called upon completion of message delivery and the
 * message is removed from the outqueue. Additional delivery information
 * can be found in msg->audit: rejected messages (0x040000 (IPADRJCT)) and
 * purged messages (0x010000 (IPADPGNR)).
 *
 * Locking:     struct hvc_iucv_private->lock
 */
static void hvc_iucv_msg_complete(struct iucv_path *path,
                                  struct iucv_message *msg)
{
        struct hvc_iucv_private *priv = path->private;
        struct iucv_tty_buffer  *ent, *next;
        LIST_HEAD(list_remove);

        spin_lock(&priv->lock);
        list_for_each_entry_safe(ent, next, &priv->tty_outqueue, list)
                if (ent->msg.id == msg->id) {
                        list_move(&ent->list, &list_remove);
                        break;
                }
        spin_unlock(&priv->lock);
        destroy_tty_buffer_list(&list_remove);
}


/* HVC operations */
static struct hv_ops hvc_iucv_ops = {
        .get_chars = hvc_iucv_get_chars,
        .put_chars = hvc_iucv_put_chars,
        .notifier_add = hvc_iucv_notifier_add,
        .notifier_del = hvc_iucv_notifier_del,
        .notifier_hangup = hvc_iucv_notifier_hangup,
};

/**
 * hvc_iucv_alloc() - Allocates a new struct hvc_iucv_private instance
 * @id: hvc_iucv_table index
 *
 * This function allocates a new hvc_iucv_private struct and put the
 * instance into hvc_iucv_table at index @id.
 * Returns 0 on success; otherwise non-zero.
 */
static int __init hvc_iucv_alloc(int id)
{
        struct hvc_iucv_private *priv;
        char name[9];
        int rc;

        priv = kzalloc(sizeof(struct hvc_iucv_private), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        spin_lock_init(&priv->lock);
        INIT_LIST_HEAD(&priv->tty_outqueue);
        INIT_LIST_HEAD(&priv->tty_inqueue);

        /* Finally allocate hvc */
        priv->hvc = hvc_alloc(HVC_IUCV_MAGIC + id,
                              HVC_IUCV_MAGIC + id, &hvc_iucv_ops, PAGE_SIZE);
        if (IS_ERR(priv->hvc)) {
                rc = PTR_ERR(priv->hvc);
                kfree(priv);
                return rc;
        }

        /* setup iucv related information */
        snprintf(name, 9, "ihvc%-4d", id);
        memcpy(priv->srv_name, name, 8);
        ASCEBC(priv->srv_name, 8);

        hvc_iucv_table[id] = priv;
        return 0;
}

/**
 * hvc_iucv_init() - Initialization of HVC backend for z/VM IUCV
 */
static int __init hvc_iucv_init(void)
{
        int rc, i;

        if (!MACHINE_IS_VM) {
                pr_warning("The z/VM IUCV Hypervisor console cannot be "
                           "used without z/VM.\n");
                return -ENODEV;
        }

        if (!hvc_iucv_devices)
                return -ENODEV;

        if (hvc_iucv_devices > MAX_HVC_IUCV_LINES)
                return -EINVAL;

        hvc_iucv_buffer_cache = kmem_cache_create(KMSG_COMPONENT,
                                           sizeof(struct iucv_tty_buffer),
                                           0, 0, NULL);
        if (!hvc_iucv_buffer_cache) {
                pr_err("Not enough memory for driver initialization "
                        "(rs=%d).\n", 1);
                return -ENOMEM;
        }

        hvc_iucv_mempool = mempool_create_slab_pool(MEMPOOL_MIN_NR,
                                                    hvc_iucv_buffer_cache);
        if (!hvc_iucv_mempool) {
                pr_err("Not enough memory for driver initialization "
                        "(rs=%d).\n", 2);
                kmem_cache_destroy(hvc_iucv_buffer_cache);
                return -ENOMEM;
        }

        /* allocate hvc_iucv_private structs */
        for (i = 0; i < hvc_iucv_devices; i++) {
                rc = hvc_iucv_alloc(i);
                if (rc) {
                        pr_err("Could not create new z/VM IUCV HVC backend "
                                "rc=%d.\n", rc);
                        goto out_error_hvc;
                }
        }

        /* register IUCV callback handler */
        rc = iucv_register(&hvc_iucv_handler, 0);
        if (rc) {
                pr_err("Could not register iucv handler (rc=%d).\n", rc);
                goto out_error_iucv;
        }

        return 0;

out_error_iucv:
        iucv_unregister(&hvc_iucv_handler, 0);
out_error_hvc:
        for (i = 0; i < hvc_iucv_devices; i++)
                if (hvc_iucv_table[i]) {
                        if (hvc_iucv_table[i]->hvc)
                                hvc_remove(hvc_iucv_table[i]->hvc);
                        kfree(hvc_iucv_table[i]);
                }
        mempool_destroy(hvc_iucv_mempool);
        kmem_cache_destroy(hvc_iucv_buffer_cache);
        return rc;
}

/**
 * hvc_iucv_console_init() - Early console initialization
 */
static  int __init hvc_iucv_console_init(void)
{
        if (!MACHINE_IS_VM || !hvc_iucv_devices)
                return -ENODEV;
        return hvc_instantiate(HVC_IUCV_MAGIC, 0, &hvc_iucv_ops);
}

/**
 * hvc_iucv_config() - Parsing of hvc_iucv=  kernel command line parameter
 * @val:        Parameter value (numeric)
 */
static  int __init hvc_iucv_config(char *val)
{
         return strict_strtoul(val, 10, &hvc_iucv_devices);
}


module_init(hvc_iucv_init);
console_initcall(hvc_iucv_console_init);
__setup("hvc_iucv=", hvc_iucv_config);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("HVC back-end for z/VM IUCV.");
MODULE_AUTHOR("Hendrik Brueckner <brueckner@linux.vnet.ibm.com>");