[PATCHv3 08/10] xshm: Character device for XSHM channel access.

[Sjur BrÃndeland]

This patch introduces a character interface to the XSHM channels.
A misc device is created, providing asynchronous IO and management.

The character device implements ring-buffer handling, copying
data directly from the Shared Memory area into user buffers.

Signed-off-by: Sjur BrÃndeland <sjur.brandeland@xxxxxxxxxxxxxx>
---
 drivers/xshm/xshm_chr.c | 1262 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 1262 insertions(+), 0 deletions(-)
 create mode 100644 drivers/xshm/xshm_chr.c

diff --git a/drivers/xshm/xshm_chr.c b/drivers/xshm/xshm_chr.c
new file mode 100644
index 0000000..6951a90
--- /dev/null
+++ b/drivers/xshm/xshm_chr.c
@@ -0,0 +1,1262 @@
+/*
+ * Copyright (C) ST-Ericsson AB 2011
+ * Author:	Per Sigmond / Per.Sigmond@xxxxxxxxxxxxxx
+ *		Sjur BrÃndeland / sjur.brandeland@xxxxxxxxxxxxxx
+ * License terms: GNU General Public License (GPL) version 2
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s :" fmt, __func__
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/uaccess.h>
+#include <asm/uaccess.h>
+#include <asm/atomic.h>
+#include <linux/xshm/xshm_dev.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sjur BrÃndland <sjur.brandeland@xxxxxxxxxxxxxx>");
+
+static LIST_HEAD(xshmchr_chrdev_list);
+static spinlock_t list_lock;
+
+#define xdev_dbg(dev, fmt, arg...) \
+		dev_dbg(dev->misc.this_device, pr_fmt(fmt), ##arg)
+
+#define xdev_vdbg(dev, fmt, arg...) \
+		dev_vdbg(dev->misc.this_device, pr_fmt(fmt), ##arg)
+
+#define pr_xchrstate(dev, str, arg...)			\
+	xdev_vdbg(dev, str " State: %s %s\n", ##arg,	\
+		STATE_IS_PENDING(dev) ? "pending" : "", \
+		STATE_IS_OPEN(dev) ? "open" : "close")
+
+#define OPEN_TOUT			(25 * HZ)
+#define CONN_STATE_OPEN_BIT		0
+#define CONN_STATE_PENDING_BIT		1
+#define CONN_REMOTE_TEARDOWN_BIT	2
+#define CONN_EOF_BIT			4
+
+#define STATE_IS_OPEN(dev) test_bit(CONN_STATE_OPEN_BIT, \
+					(void *) &(dev)->conn_state)
+#define STATE_IS_REMOTE_TEARDOWN(dev) test_bit(CONN_REMOTE_TEARDOWN_BIT, \
+					(void *) &(dev)->conn_state)
+#define STATE_IS_PENDING(dev) test_bit(CONN_STATE_PENDING_BIT, \
+					(void *) &(dev)->conn_state)
+#define SET_STATE_OPEN(dev) (set_bit(CONN_STATE_OPEN_BIT,	\
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_STATE_OPEN:%d\n", dev->conn_state))
+#define SET_STATE_CLOSED(dev) (clear_bit(CONN_STATE_OPEN_BIT,	\
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_STATE_CLOSED:%d\n", dev->conn_state))
+#define SET_PENDING_ON(dev) (set_bit(CONN_STATE_PENDING_BIT,	\
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_PENDING_ON:%d\n", dev->conn_state))
+#define SET_PENDING_OFF(dev) (clear_bit(CONN_STATE_PENDING_BIT, \
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_PENDING_OFF:%d\n", dev->conn_state))
+#define SET_REMOTE_TEARDOWN(dev) (set_bit(CONN_REMOTE_TEARDOWN_BIT,	\
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_REMOTE_TEARDOWN:%d\n", dev->conn_state))
+#define CLEAR_REMOTE_TEARDOWN(dev) (clear_bit(CONN_REMOTE_TEARDOWN_BIT, \
+			(void *) &(dev)->conn_state), \
+			pr_devel("CLEAR_REMOTE_TEARDOWN:%d\n", dev->conn_state))
+#define SET_EOF(dev) (set_bit(CONN_EOF_BIT,	\
+			(void *) &(dev)->conn_state), \
+			pr_devel("SET_EOF:%d\n", dev->conn_state))
+#define CLEAR_EOF(dev) (clear_bit(CONN_EOF_BIT, \
+			(void *) &(dev)->conn_state), \
+			pr_devel("CLEAR_EOF:%d\n", dev->conn_state))
+#define STATE_IS_EOF(dev) test_bit(CONN_EOF_BIT, \
+					(void *) &(dev)->conn_state)
+
+#define CHR_READ_FLAG 0x01
+#define CHR_WRITE_FLAG 0x02
+
+#ifdef CONFIG_DEBUG_FS
+static struct dentry *debugfsdir;
+#include <linux/debugfs.h>
+#define	dbfs_atomic_inc(a) atomic_inc(a)
+#define	dbfs_atomic_add(v, a) atomic_add_return(v, a)
+#else
+#define	dbfs_atomic_inc(a) 0
+#define	dbfs_atomic_add(v, a) 0
+#endif
+
+struct ringbuf {
+	__le32 *ri;	/* Pointer to read-index in shared memory.*/
+	__le32 *wi;	/* Pointer to write-index in shared memory */
+	unsigned int size;/* Size of buffer */
+	void *data;	/* Buffer data in shared memory */
+};
+
+struct xshmchr_char_dev {
+	struct xshm_dev *xshm;
+	struct kref kref;
+	struct ringbuf rx, tx;
+	u32 conn_state;
+	char name[256];
+	struct miscdevice misc;
+	int file_mode;
+
+	/* Access to this struct and below layers */
+	struct mutex mutex;
+	wait_queue_head_t mgmt_wq;
+	/* List of misc test devices */
+	struct list_head list_field;
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *debugfs_device_dir;
+	atomic_t num_open;
+	atomic_t num_close;
+	atomic_t num_read;
+	atomic_t num_read_block;
+	atomic_t num_read_bytes;
+
+	atomic_t num_write;
+	atomic_t num_write_block;
+	atomic_t num_write_bytes;
+
+	atomic_t num_init;
+	atomic_t num_init_resp;
+	atomic_t num_deinit;
+	atomic_t num_deinit_resp;
+	atomic_t num_remote_teardown_ind;
+
+#endif
+};
+
+static void xshm_release(struct kref *kref)
+{
+	struct xshmchr_char_dev *dev;
+	dev = container_of(kref, struct xshmchr_char_dev, kref);
+	xdev_vdbg(dev, "Freeing device\n");
+	kfree(dev);
+}
+
+static void xshmchr_get(struct xshmchr_char_dev *dev)
+{
+	kref_get(&dev->kref);
+}
+
+static void xshmchr_put(struct xshmchr_char_dev *dev)
+{
+	kref_put(&dev->kref, xshm_release);
+}
+
+static inline unsigned int ringbuf_empty(struct ringbuf *rb)
+{
+	return *rb->wi == *rb->ri;
+}
+
+static inline unsigned int ringbuf_full(struct ringbuf *rb)
+{
+	return (le32_to_cpu(*rb->wi) + 1) % rb->size == le32_to_cpu(*rb->ri);
+}
+
+static int insert_ringbuf(struct ringbuf *rb, const char __user *from,
+		u32 len)
+{
+	u32 wi = le32_to_cpu(*rb->wi);
+	u32 ri = le32_to_cpu(*rb->ri);
+	u32 cpylen, cpylen2 = 0, notcpy;
+
+	pr_devel("insert: wi:%d ri:%d len:%d\n", wi, ri, len);
+	if (wi >= ri) {
+		len = min(len, rb->size - 1 - wi + ri);
+		cpylen = min(rb->size, wi + len) - wi;
+
+		/* Write is ahead of read, copy 'cpylen' data from 'wi' */
+		notcpy = copy_from_user(rb->data + wi, from, cpylen);
+		if (cpylen > 0 && notcpy == cpylen)
+			return -EIO;
+
+		if (cpylen < len && notcpy == 0) {
+			cpylen2 = min(ri - 1 , len - cpylen);
+
+			/* We have wrapped copy 'cpylen2' from start */
+			notcpy = copy_from_user(rb->data, from + cpylen,
+					cpylen2);
+		}
+	} else {
+		cpylen = min(ri - 1 - wi , len);
+
+		/* Read is ahead of write, copy from wi to (ri - 1) */
+		notcpy = copy_from_user(rb->data + wi, from, cpylen);
+		if (cpylen > 0 && notcpy == cpylen)
+			return -EIO;
+
+	}
+	/* Do write barrier before updating index */
+	smp_wmb();
+	*rb->wi = cpu_to_le32((wi + cpylen + cpylen2 - notcpy) % rb->size);
+	pr_devel("write ringbuf: wi: %d->%d l:%d\n",
+			wi, le32_to_cpu(*rb->wi), cpylen + cpylen2);
+	return cpylen + cpylen2 - notcpy;
+}
+
+static int extract_ringbuf(struct ringbuf *rb, void __user *to, u32 len)
+{
+	u32 wi = le32_to_cpu(*rb->wi);
+	u32 ri = le32_to_cpu(*rb->ri);
+	u32 cpylen = 0, cpylen2 = 0, notcpy;
+
+	pr_devel("extract: wi:%d ri:%d len:%d\n", wi, ri, len);
+	if (ri <= wi) {
+		len = min(wi - ri, len);
+
+		/* Read is ahead of write, copy 'len' data from 'ri' */
+		notcpy = copy_to_user(to, rb->data + ri, len);
+		if (len > 0 && notcpy == len)
+			return -EIO;
+
+		/* Do write barrier before updating index */
+		smp_wmb();
+		*rb->ri = cpu_to_le32(ri + len - notcpy);
+		pr_devel("read ringbuf: ri: %d->%d len:%d\n",
+			ri, le32_to_cpu(*rb->ri), len - notcpy);
+
+		return len - notcpy;
+	} else {
+		/* wr >= ri */
+		cpylen = min(rb->size - ri, len);
+
+		/* Write is ahead, copy 'cpylen' data from ri until end */
+		notcpy = copy_to_user(to, rb->data + ri, cpylen);
+		if (cpylen > 0 && notcpy == cpylen)
+			return -EIO;
+		if (cpylen < len && notcpy == 0) {
+			cpylen2 = min(wi , len - cpylen);
+			/* we have wrapped copy from [0 .. cpylen2] */
+			notcpy = copy_to_user(to + cpylen, rb->data, cpylen2);
+		}
+		/* Do write barrier before updating index */
+		smp_wmb();
+
+		*rb->ri = cpu_to_le32((ri + cpylen + cpylen2 - notcpy)
+						% rb->size);
+		pr_devel("read ringbuf: ri: %d->%d cpylen:%d\n",
+			ri, le32_to_cpu(*rb->ri), cpylen + cpylen2 - notcpy);
+
+		return cpylen + cpylen2 - notcpy;
+	}
+}
+
+static void drain_ringbuf(struct xshmchr_char_dev *dev)
+{
+	/* Empty the ringbuf. */
+	*dev->xshm->cfg.rx.read = *dev->xshm->cfg.rx.write;
+	*dev->xshm->cfg.tx.write = *dev->xshm->cfg.tx.read;
+}
+
+static int open_cb(void *drv)
+{
+	struct xshmchr_char_dev *dev = drv;
+
+	pr_xchrstate(dev, "enter");
+	dbfs_atomic_inc(&dev->num_init_resp);
+	/* Signal reader that data is available. */
+	WARN_ON(!STATE_IS_OPEN(dev));
+	SET_PENDING_OFF(dev);
+	wake_up_interruptible_all(&dev->mgmt_wq);
+	pr_xchrstate(dev, "exit");
+	return 0;
+}
+
+static void close_cb(void *drv)
+{
+	struct xshmchr_char_dev *dev = drv;
+
+	pr_xchrstate(dev, "enter");
+	dbfs_atomic_inc(&dev->num_remote_teardown_ind);
+	if (STATE_IS_PENDING(dev) && !STATE_IS_OPEN(dev)) {
+		/* Normal close sequence */
+		SET_PENDING_OFF(dev);
+		CLEAR_REMOTE_TEARDOWN(dev);
+		SET_EOF(dev);
+		drain_ringbuf(dev);
+		dev->file_mode = 0;
+	} else {
+		/* Remote teardown, close should be called from user-space */
+		SET_REMOTE_TEARDOWN(dev);
+		SET_PENDING_OFF(dev);
+	}
+
+	wake_up_interruptible_all(&dev->mgmt_wq);
+	pr_xchrstate(dev, "exit");
+}
+
+static int ipc_rx_cb(void *drv)
+{
+	struct xshmchr_char_dev *dev = drv;
+
+	xdev_vdbg(dev, "enter\n");
+
+	if (unlikely(*dev->xshm->cfg.rx.state == cpu_to_le32(XSHM_CLOSED)))
+		return -ESHUTDOWN;
+
+	/*
+	 * Performance could perhaps be improved by having a WAIT
+	 * flag, similar to SOCK_ASYNC_WAITDATA, and only do wake up
+	 * when it's actually needed.
+	 */
+	wake_up_interruptible_all(&dev->mgmt_wq);
+	return 0;
+}
+
+static int ipc_tx_release_cb(void *drv)
+{
+	struct xshmchr_char_dev *dev = drv;
+
+	xdev_vdbg(dev, "enter\n");
+	wake_up_interruptible_all(&dev->mgmt_wq);
+	return 0;
+}
+
+/* Device Read function called from Linux kernel */
+static ssize_t xshmchr_chrread(struct file *filp, char __user *buf,
+	 size_t count, loff_t *f_pos)
+{
+	unsigned int len = 0;
+	int result;
+	struct xshmchr_char_dev *dev = filp->private_data;
+	ssize_t ret = -EIO;
+
+	if (dev == NULL) {
+		xdev_dbg(dev, "private_data not set!\n");
+		return -EBADFD;
+	}
+
+	/* I want to be alone on dev (except status and queue) */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		return -ERESTARTSYS;
+	}
+	xshmchr_get(dev);
+
+	if (!STATE_IS_OPEN(dev)) {
+		/* Device is closed or closing. */
+		if (!STATE_IS_PENDING(dev)) {
+			xdev_dbg(dev, "device is closed (by remote)\n");
+			ret = -ECONNRESET;
+		} else {
+			xdev_dbg(dev, "device is closing...\n");
+			ret = -EBADF;
+		}
+		goto read_error;
+	}
+
+	dbfs_atomic_inc(&dev->num_read);
+
+	/* Device is open or opening. */
+	if (STATE_IS_PENDING(dev)) {
+		xdev_vdbg(dev, "device is opening...\n");
+
+		dbfs_atomic_inc(&dev->num_read_block);
+		if (filp->f_flags & O_NONBLOCK) {
+			/* We can't block. */
+			xdev_dbg(dev, "exit: state pending and O_NONBLOCK\n");
+			ret = -EAGAIN;
+			goto read_error;
+		}
+
+		/*
+		 * To reach here client must do blocking open,
+		 * and start read() before open completes. This is
+		 * quite quirky, but let's handle it anyway.
+		 */
+		result =
+		    wait_event_interruptible(dev->mgmt_wq,
+					!STATE_IS_PENDING(dev) ||
+				    STATE_IS_REMOTE_TEARDOWN(dev));
+
+		if (result == -ERESTARTSYS) {
+			xdev_dbg(dev, "wait_event_interruptible"
+				 " woken by a signal (1)\n");
+			ret = -ERESTARTSYS;
+			goto read_error;
+		}
+		if (STATE_IS_REMOTE_TEARDOWN(dev)) {
+			xdev_dbg(dev,
+				"received remote_shutdown indication (1)\n");
+			ret = -ESHUTDOWN;
+			goto read_error;
+		}
+	}
+
+	/* Block if we don't have any received buffers.
+	 * The queue has its own lock.
+	 */
+	while (ringbuf_empty(&dev->rx)) {
+
+		if (filp->f_flags & O_NONBLOCK) {
+			xdev_vdbg(dev, "exit: O_NONBLOCK\n");
+			ret = -EAGAIN;
+			goto read_error;
+		}
+
+		/* Let writers in. */
+		mutex_unlock(&dev->mutex);
+
+		xdev_vdbg(dev, "wait for data\n");
+		/* Block reader until data arrives or device is closed. */
+		if (wait_event_interruptible(dev->mgmt_wq,
+				!ringbuf_empty(&dev->rx)
+				|| STATE_IS_REMOTE_TEARDOWN(dev)
+				|| !STATE_IS_OPEN(dev)) == -ERESTARTSYS) {
+			xdev_vdbg(dev, "event_interruptible woken by "
+				 "a signal, signal_pending(current) = %d\n",
+				signal_pending(current));
+			return -ERESTARTSYS;
+		}
+
+		xdev_vdbg(dev, "wakeup readq\n");
+
+		if (STATE_IS_REMOTE_TEARDOWN(dev) && ringbuf_empty(&dev->rx)) {
+			if (!STATE_IS_EOF(dev)) {
+				xdev_dbg(dev, "First EOF OK\n");
+				SET_EOF(dev);
+				ret = 0;
+				goto error_nolock;
+			}
+			xdev_dbg(dev, "2'nd EOF - remote_shutdown\n");
+			ret = -ECONNRESET;
+			goto error_nolock;
+		}
+
+		/* I want to be alone on dev (except status and queue). */
+		if (mutex_lock_interruptible(&dev->mutex)) {
+			xdev_dbg(dev, "mutex_lock_interruptible"
+					" got signalled\n");
+			return -ERESTARTSYS;
+		}
+
+		if (!STATE_IS_OPEN(dev)) {
+			/* Someone closed the link, report error. */
+			xdev_dbg(dev, "remote end shutdown!\n");
+			ret = -EBADF;
+			goto read_error;
+		}
+	}
+
+	xdev_vdbg(dev, "copy data\n");
+	len = extract_ringbuf(&dev->rx, buf, count);
+	if (len <= 0) {
+		xdev_dbg(dev, "Extracting from ringbuf failed\n");
+		ret = -EINVAL;
+		goto read_error;
+	}
+
+	/* Signal to modem that data is read from ringbuf */
+
+	dev->xshm->ipc_rx_release(dev->xshm, false);
+
+	dbfs_atomic_add(len, &dev->num_read_bytes);
+	/* Let the others in. */
+	mutex_unlock(&dev->mutex);
+	xshmchr_put(dev);
+	return len;
+
+read_error:
+	mutex_unlock(&dev->mutex);
+error_nolock:
+	xshmchr_put(dev);
+	return ret;
+}
+
+/* Device write function called from Linux kernel (misc device) */
+static ssize_t xshmchr_chrwrite(struct file *filp, const char __user *buf,
+		      size_t count, loff_t *f_pos)
+{
+	struct xshmchr_char_dev *dev = filp->private_data;
+	ssize_t ret = -EIO;
+	int result;
+	uint len = 0;
+
+	if (dev == NULL) {
+		xdev_dbg(dev, "private_data not set!\n");
+		ret = -EBADFD;
+		goto write_error_no_unlock;
+	}
+
+	pr_xchrstate(dev, "enter");
+
+	/* I want to be alone on dev (except status and queue). */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		ret = -ERESTARTSYS;
+		goto write_error_no_unlock;
+	}
+	xshmchr_get(dev);
+
+	dbfs_atomic_inc(&dev->num_write);
+	if (!STATE_IS_OPEN(dev)) {
+		/* Device is closed or closing. */
+		if (!STATE_IS_PENDING(dev)) {
+			xdev_dbg(dev, "device is closed (by remote)\n");
+			ret = -EPIPE;
+		} else {
+			xdev_dbg(dev, "device is closing...\n");
+			ret = -EBADF;
+		}
+		goto write_error;
+	}
+
+	/* Device is open or opening. */
+	if (STATE_IS_PENDING(dev)) {
+		xdev_dbg(dev, "device is opening...\n");
+
+		dbfs_atomic_inc(&dev->num_write_block);
+		if (filp->f_flags & O_NONBLOCK) {
+			/* We can't block */
+			xdev_dbg(dev, "exit: state pending and O_NONBLOCK\n");
+			ret = -EAGAIN;
+			goto write_error;
+		}
+
+		/* Blocking mode; state is pending and we need to wait
+		 * for its conclusion. (Shutdown_ind set pending off.)
+		 */
+		result =
+		    wait_event_interruptible(dev->mgmt_wq,
+					!STATE_IS_PENDING(dev) ||
+					STATE_IS_REMOTE_TEARDOWN(dev));
+		if (result == -ERESTARTSYS) {
+			xdev_dbg(dev, "wait_event_interruptible"
+				 " woken by a signal (1)\n");
+			ret = -ERESTARTSYS;
+			goto write_error;
+		}
+	}
+	if (STATE_IS_REMOTE_TEARDOWN(dev)) {
+		xdev_dbg(dev, "received remote_shutdown indication\n");
+		ret = -EPIPE;
+		goto write_error;
+	}
+
+	while (ringbuf_full(&dev->tx)) {
+		/* Flow is off. Check non-block flag. */
+		if (filp->f_flags & O_NONBLOCK) {
+			xdev_dbg(dev, "exit: O_NONBLOCK and tx flow off");
+			ret = -EAGAIN;
+			goto write_error;
+		}
+
+		/* Let readers in. */
+		mutex_unlock(&dev->mutex);
+
+		xdev_vdbg(dev, "wait for write space\n");
+		/* Wait until flow is on or device is closed. */
+		if (wait_event_interruptible(dev->mgmt_wq,
+					!ringbuf_full(&dev->tx)
+					|| !STATE_IS_OPEN(dev)
+					|| STATE_IS_REMOTE_TEARDOWN(dev)
+					) == -ERESTARTSYS) {
+			xdev_dbg(dev, "wait_event_interruptible"
+				 " woken by a signal (1)\n");
+			ret = -ERESTARTSYS;
+			goto write_error_no_unlock;
+		}
+
+		/* I want to be alone on dev (except status and queue). */
+		if (mutex_lock_interruptible(&dev->mutex)) {
+			xdev_dbg(dev, "mutex_lock_interruptible "
+					"got signalled\n");
+			ret = -ERESTARTSYS;
+			goto write_error_no_unlock;
+		}
+
+		xdev_vdbg(dev, "wakeup got write space\n");
+		if (!STATE_IS_OPEN(dev)) {
+			/* Someone closed the link, report error. */
+			xdev_dbg(dev, "remote end shutdown!\n");
+			ret = -EPIPE;
+			goto write_error;
+		}
+		if (STATE_IS_REMOTE_TEARDOWN(dev)) {
+			xdev_dbg(dev, "received remote_shutdown indication\n");
+			ret = -ESHUTDOWN;
+			goto write_error;
+		}
+	}
+	len = insert_ringbuf(&dev->tx, buf, count);
+	xdev_vdbg(dev, "inserted %d bytes\n", len);
+	if (len <= 0) {
+		xdev_dbg(dev, "transmit failed, error = %d\n",
+				(int) ret);
+		goto write_error;
+	}
+
+	dbfs_atomic_add(len, &dev->num_write_bytes);
+
+	/* Signal to modem that data is put in ringbuf */
+	dev->xshm->ipc_tx(dev->xshm);
+
+	mutex_unlock(&dev->mutex);
+	xshmchr_put(dev);
+	return len;
+
+write_error:
+	mutex_unlock(&dev->mutex);
+write_error_no_unlock:
+	xshmchr_put(dev);
+	return ret;
+}
+
+static unsigned int xshmchr_chrpoll(struct file *filp, poll_table *waittab)
+{
+	struct xshmchr_char_dev *dev = filp->private_data;
+	unsigned int mask = 0;
+
+	if (dev == NULL) {
+		xdev_dbg(dev, "private_data not set!\n");
+		return -EBADFD;
+	}
+
+	/* I want to be alone on dev (except status and queue). */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		mask |= POLLERR;
+		goto out_unlocked;
+	}
+	xshmchr_get(dev);
+
+	if (STATE_IS_REMOTE_TEARDOWN(dev)) {
+		xdev_dbg(dev, "not open\n");
+		mask |= POLLRDHUP | POLLHUP;
+		goto out;
+	}
+
+	xdev_vdbg(dev, "poll wait\n");
+	poll_wait(filp, &dev->mgmt_wq, waittab);
+
+	if (STATE_IS_OPEN(dev) && STATE_IS_PENDING(dev))
+		goto out;
+
+	if (!ringbuf_empty(&dev->rx))
+		mask |= (POLLIN | POLLRDNORM);
+
+	if (!ringbuf_full(&dev->tx))
+		mask |= (POLLOUT | POLLWRNORM);
+
+out:
+	mutex_unlock(&dev->mutex);
+out_unlocked:
+	xdev_vdbg(dev, "poll return mask=0x%04x\n", mask);
+	xshmchr_put(dev);
+	return mask;
+}
+
+/* Usage:
+ * minor >= 0 : find from minor
+ * minor < 0 and name == name : find from name
+ * minor < 0 and name == NULL : get first
+ */
+
+static struct xshmchr_char_dev *find_device(int minor, char *name,
+					 int remove_from_list)
+{
+	struct list_head *list_node;
+	struct list_head *n;
+	struct xshmchr_char_dev *dev = NULL;
+	struct xshmchr_char_dev *tmp;
+	spin_lock(&list_lock);
+	pr_devel("start looping\n");
+	list_for_each_safe(list_node, n, &xshmchr_chrdev_list) {
+		tmp = list_entry(list_node, struct xshmchr_char_dev,
+				list_field);
+		if (minor >= 0) {	/* find from minor */
+			if (tmp->misc.minor == minor)
+				dev = tmp;
+
+		} else if (name) {	/* find from name */
+			if (!strncmp(tmp->name, name, sizeof(tmp->name)))
+				dev = tmp;
+		} else {	/* take first */
+			dev = tmp;
+		}
+
+		if (dev) {
+			xdev_vdbg(dev, "match %d, %s\n",
+				      minor, name);
+			if (remove_from_list)
+				list_del(list_node);
+			break;
+		}
+	}
+	spin_unlock(&list_lock);
+	return dev;
+}
+
+static int xshmchr_chropen(struct inode *inode, struct file *filp)
+{
+	struct xshmchr_char_dev *dev = NULL;
+	int result = -1;
+	int minor = iminor(inode);
+	int mode = 0;
+	int ret = -EIO;
+
+	dev = find_device(minor, NULL, 0);
+	pr_xchrstate(dev, "enter");
+
+	if (dev == NULL) {
+		xdev_dbg(dev, "Could not find device\n");
+		return -EBADF;
+	}
+
+	/* I want to be alone on dev (except status and queue). */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		return -ERESTARTSYS;
+	}
+
+	xshmchr_get(dev);
+	dbfs_atomic_inc(&dev->num_open);
+	filp->private_data = dev;
+
+	switch (filp->f_flags & O_ACCMODE) {
+	case O_RDONLY:
+		mode = CHR_READ_FLAG;
+		break;
+	case O_WRONLY:
+		mode = CHR_WRITE_FLAG;
+		break;
+	case O_RDWR:
+		mode = CHR_READ_FLAG | CHR_WRITE_FLAG;
+		break;
+	}
+
+	/* If device is not open, make sure device is in fully closed state. */
+	if (!STATE_IS_OPEN(dev)) {
+		/* Has link close response been received
+		 * (if we ever sent it)?
+		 */
+		if (STATE_IS_PENDING(dev)) {
+			/* Still waiting for close response from remote.
+			 * If opened non-blocking, report "would block".
+			 */
+			if (filp->f_flags & O_NONBLOCK) {
+				xdev_vdbg(dev,
+					"exit: O_NONBLOCK && close pending\n");
+				ret = -EAGAIN;
+				goto open_error;
+			}
+
+			xdev_vdbg(dev, "WAIT for close response from remote\n");
+
+			/*
+			 * Blocking mode; close is pending and we need to wait
+			 * for its conclusion. However modem may be dead,
+			 * or resureccted and alive waiting for
+			 * an open ack.
+			 * It's hard to get this rigth - if state is
+			 * pending. We have missed a state update,
+			 * let's just wait for ack, and then proceede
+			 * with watever state we have.
+			 */
+			result =
+			    wait_event_interruptible_timeout(dev->mgmt_wq,
+					    !STATE_IS_PENDING(dev) ||
+					    STATE_IS_REMOTE_TEARDOWN(dev),
+					    OPEN_TOUT);
+
+			if (result == -ERESTARTSYS) {
+				xdev_dbg(dev, "wait_event_interruptible"
+					" woken by a signal (1)\n");
+				ret = -ERESTARTSYS;
+				goto open_error;
+			}
+
+			if (result == 0) {
+				SET_PENDING_OFF(dev);
+				pr_xchrstate(dev,
+				    "Timeout -pending close -Clear pending");
+			} else
+				pr_xchrstate(dev, "wakeup (wait for close)");
+		}
+	}
+
+	/* Device is now either closed, pending open or open */
+	if (STATE_IS_OPEN(dev) && !STATE_IS_PENDING(dev)) {
+		/* Open */
+		xdev_vdbg(dev, "Device is already opened (dev=%p) check"
+				"access f_flags = 0x%x file_mode = 0x%x\n",
+				dev, mode, dev->file_mode);
+
+		if (mode & dev->file_mode) {
+			xdev_vdbg(dev, "Access mode already in use 0x%x\n",
+					mode);
+			ret = -EBUSY;
+			goto open_error;
+		}
+	} else {
+
+		/* We are closed or pending open.
+		 * If closed:	    send link setup
+		 * If pending open: link setup already sent (we could have been
+		 *		    interrupted by a signal last time)
+		 */
+		if (!STATE_IS_OPEN(dev)) {
+			/* First opening of file; do connect */
+
+			SET_STATE_OPEN(dev);
+			SET_PENDING_ON(dev);
+			CLEAR_EOF(dev);
+			/* Send "open" by resetting indexes */
+			result = dev->xshm->open(dev->xshm);
+
+			if (result < 0) {
+				xdev_dbg(dev, "can't open channel\n");
+				ret = -EIO;
+				SET_STATE_CLOSED(dev);
+				SET_PENDING_OFF(dev);
+				goto open_error;
+			}
+			dbfs_atomic_inc(&dev->num_init);
+		}
+
+		/* If opened non-blocking, report "success".
+		 */
+		if (filp->f_flags & O_NONBLOCK) {
+			xdev_vdbg(dev, "EXIT: O_NONBLOCK success\n");
+			ret = 0;
+			goto open_success;
+		}
+
+		xdev_vdbg(dev, "WAIT for connect response\n");
+		/*
+		 * misc_open holds a global mutex anyway so there is no
+		 * reason to release our own while waiting
+		 */
+		result =
+		    wait_event_interruptible_timeout(dev->mgmt_wq,
+				    !STATE_IS_PENDING(dev) ||
+				    STATE_IS_REMOTE_TEARDOWN(dev),
+				    OPEN_TOUT);
+		if (result == 0) {
+			xdev_dbg(dev, "wait_event_interruptible timeout (1)\n");
+			ret = -ETIMEDOUT;
+			goto open_error;
+		}
+		if (result == -ERESTARTSYS) {
+			xdev_dbg(dev, "wait_event_interruptible woken by sig");
+			ret = -ERESTARTSYS;
+			goto open_error;
+		}
+		if (STATE_IS_REMOTE_TEARDOWN(dev)) {
+			xdev_dbg(dev, "received remote_shutdown indication\n");
+			ret = -ESHUTDOWN;
+			goto open_error;
+		}
+
+		pr_xchrstate(dev, "wakeup (wait for open)");
+		if (!STATE_IS_OPEN(dev)) {
+			/* Lower layers said "no". */
+			xdev_dbg(dev, "xshmchr_chropen: Closed received\n");
+			ret = -EPIPE;
+			goto open_error;
+		}
+
+		xdev_vdbg(dev, "connect received\n");
+	}
+open_success:
+	/* Open is OK. */
+	dev->file_mode |= mode;
+
+	xdev_vdbg(dev, "file mode = %x\n", dev->file_mode);
+	pr_xchrstate(dev, "exit");
+
+	mutex_unlock(&dev->mutex);
+	xshmchr_put(dev);
+	return 0;
+
+open_error:
+	dev->xshm->close(dev->xshm);
+	SET_STATE_CLOSED(dev);
+	SET_PENDING_OFF(dev);
+	mutex_unlock(&dev->mutex);
+	xshmchr_put(dev);
+	return ret;
+}
+
+static int xshmchr_chrrelease(struct inode *inode, struct file *filp)
+{
+	struct xshmchr_char_dev *dev = NULL;
+	int minor = iminor(inode);
+	int mode = 0;
+
+
+	dev = find_device(minor, NULL, 0);
+	if (dev == NULL) {
+		xdev_dbg(dev, "Could not find device\n");
+		return -EBADF;
+	}
+
+	pr_xchrstate(dev, "enter");
+
+	/* I want to be alone on dev (except status queue). */
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		return -ERESTARTSYS;
+	}
+
+	xshmchr_get(dev);
+	dbfs_atomic_inc(&dev->num_close);
+
+	/* Is the device open? */
+	if (!STATE_IS_OPEN(dev)) {
+		xdev_vdbg(dev, "Device not open (dev=%p)\n",
+			      dev);
+		mutex_unlock(&dev->mutex);
+		xshmchr_put(dev);
+		return 0;
+	}
+
+	switch (filp->f_flags & O_ACCMODE) {
+	case O_RDONLY:
+		mode = CHR_READ_FLAG;
+		break;
+	case O_WRONLY:
+		mode = CHR_WRITE_FLAG;
+		break;
+	case O_RDWR:
+		mode = CHR_READ_FLAG | CHR_WRITE_FLAG;
+		break;
+	}
+
+	dev->file_mode &= ~mode;
+	if (dev->file_mode) {
+		xdev_vdbg(dev, "Device is kept open by someone else, "
+			 " don't close. XSHMCHR connection - file_mode = %x\n",
+			 dev->file_mode);
+		mutex_unlock(&dev->mutex);
+		xshmchr_put(dev);
+		return 0;
+	}
+
+	/* IS_CLOSED have double meaning:
+	 * 1) Spontanous Remote Shutdown Request.
+	 * 2) Ack on a channel teardown(disconnect)
+	 * Must clear bit, in case we previously received
+	 * a remote shudown request.
+	 */
+
+	SET_STATE_CLOSED(dev);
+	SET_PENDING_ON(dev);
+	CLEAR_REMOTE_TEARDOWN(dev);
+	SET_EOF(dev);
+
+	dev->xshm->close(dev->xshm);
+
+	dbfs_atomic_inc(&dev->num_deinit);
+
+	/* Empty the ringbuf */
+	drain_ringbuf(dev);
+	dev->file_mode = 0;
+
+	mutex_unlock(&dev->mutex);
+	pr_xchrstate(dev, "exit");
+	xshmchr_put(dev);
+	return 0;
+}
+
+static const struct file_operations xshmchr_chrfops = {
+	.owner = THIS_MODULE,
+	.read = xshmchr_chrread,
+	.write = xshmchr_chrwrite,
+	.open = xshmchr_chropen,
+	.release = xshmchr_chrrelease,
+	.poll = xshmchr_chrpoll,
+};
+
+static int cfshm_probe(struct xshm_dev *xshm)
+
+{
+	struct xshmchr_char_dev *dev = NULL;
+	int result;
+
+	pr_devel("cfshm_probe called\n");
+	if (xshm == NULL)
+		return 0;
+
+	/* Allocate device */
+	dev = kmalloc(sizeof(*dev), GFP_KERNEL);
+
+	if (!dev) {
+		pr_err("kmalloc failed.\n");
+		return -ENOMEM;
+	}
+
+	memset(dev, 0, sizeof(*dev));
+	kref_init(&dev->kref);
+
+	dev->xshm = xshm;
+	mutex_init(&dev->mutex);
+	init_waitqueue_head(&dev->mgmt_wq);
+
+	/* Fill in some information concerning the misc device. */
+	dev->misc.minor = MISC_DYNAMIC_MINOR;
+	if (strlen(xshm->cfg.name) == 0) {
+		xdev_dbg(dev, "XSHM device does not have a name\n");
+		return -EINVAL;
+	}
+	sprintf(dev->name, "%s", xshm->cfg.name);
+	dev->misc.name = dev->name;
+	dev->misc.fops = &xshmchr_chrfops;
+
+	dev->tx.ri = xshm->cfg.tx.read;
+	dev->tx.wi = xshm->cfg.tx.write;
+	dev->tx.data = xshm->cfg.tx.addr;
+	dev->tx.size = xshm->cfg.tx.ch_size - 1;
+
+	dev->rx.ri = xshm->cfg.rx.read;
+	dev->rx.wi = xshm->cfg.rx.write;
+	dev->rx.data = xshm->cfg.rx.addr;
+	dev->rx.size = xshm->cfg.rx.ch_size - 1;
+	if (dev->rx.size < 2 || dev->tx.size < 2) {
+		dev->rx.size = 0;
+		dev->tx.size = 0;
+		xdev_dbg(dev, "dev:error - channel size too small\n");
+		return -EINVAL;
+	}
+	dev->xshm->ipc_rx_cb = ipc_rx_cb;
+	dev->xshm->ipc_tx_release_cb = ipc_tx_release_cb;
+	dev->xshm->open_cb = open_cb;
+	dev->xshm->close_cb = close_cb;
+	dev->xshm->driver_data = dev;
+
+	mutex_lock(&dev->mutex);
+
+	/* Register the device. */
+	dev->misc.parent = &xshm->dev;
+	pr_devel("register dev:%s chr=%s(%s) dev=%p\n",
+			dev_name(&dev->xshm->dev),
+			dev->name, xshm->cfg.name, dev);
+	result = misc_register(&dev->misc);
+
+	/* Lock in order to try to stop someone from opening the device
+	 * too early. The misc device has its own lock. We cannot take our
+	 * lock until misc_register() is finished, because in open() the
+	 * locks are taken in this order (misc first and then dev).
+	 * So anyone managing to open the device between the misc_register
+	 * and the mutex_lock will get a "device not found" error. Don't
+	 * think it can be avoided.
+	 */
+
+	if (result < 0) {
+		pr_warn("error - %d, can't register misc\n",
+				result);
+		mutex_unlock(&dev->mutex);
+		goto err_failed;
+	}
+
+	xdev_vdbg(dev, "Registered dev with name=%s minor=%d, dev=%p\n",
+			dev->misc.name, dev->misc.minor, dev->misc.this_device);
+
+	SET_STATE_CLOSED(dev);
+	SET_PENDING_OFF(dev);
+	CLEAR_REMOTE_TEARDOWN(dev);
+	CLEAR_EOF(dev);
+
+	/* Add the device. */
+	spin_lock(&list_lock);
+	list_add(&dev->list_field, &xshmchr_chrdev_list);
+	spin_unlock(&list_lock);
+
+#ifdef CONFIG_DEBUG_FS
+	if (debugfsdir != NULL) {
+		dev->debugfs_device_dir =
+		    debugfs_create_dir(dev->misc.name, debugfsdir);
+		debugfs_create_u32("conn_state", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir, &dev->conn_state);
+		debugfs_create_u32("num_open", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_open);
+		debugfs_create_u32("num_close", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_close);
+		debugfs_create_u32("num_init", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_init);
+		debugfs_create_u32("num_init_resp", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_init_resp);
+		debugfs_create_u32("num_deinit", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_deinit);
+		debugfs_create_u32("num_deinit_resp", S_IRUSR | S_IWUSR,
+				   dev->debugfs_device_dir,
+				   (u32 *) &dev->num_deinit_resp);
+		debugfs_create_u32("num_remote_teardown_ind",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_remote_teardown_ind);
+		debugfs_create_u32("num_read",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_read);
+		debugfs_create_u32("num_read_block",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_read_block);
+		debugfs_create_u32("num_read_bytes",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_read_bytes);
+		debugfs_create_u32("num_write",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_write);
+		debugfs_create_u32("num_write_block",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_write_block);
+		debugfs_create_u32("num_write_bytes",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				   (u32 *) &dev->num_write_bytes);
+
+		debugfs_create_u32("rx_write_index",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.rx.write);
+		debugfs_create_u32("rx_read_index",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.rx.read);
+		debugfs_create_u32("rx_state",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.rx.state);
+		debugfs_create_u32("tx_write_index",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.tx.write);
+		debugfs_create_u32("tx_read_index",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.tx.read);
+		debugfs_create_u32("tx_state",
+				   S_IRUSR | S_IWUSR, dev->debugfs_device_dir,
+				(u32 *) dev->xshm->cfg.tx.state);
+
+	}
+#endif
+	mutex_unlock(&dev->mutex);
+	return 0;
+err_failed:
+	xshmchr_put(dev);
+	return result;
+}
+
+static int chrdev_remove(struct xshmchr_char_dev *dev)
+{
+	if (!dev)
+		return -EBADF;
+
+	if (STATE_IS_OPEN(dev)) {
+		xdev_dbg(dev, "Device is opened "
+			 "(dev=%p) file_mode = 0x%x\n",
+			 dev, dev->file_mode);
+		SET_STATE_CLOSED(dev);
+		SET_PENDING_OFF(dev);
+		wake_up_interruptible_all(&dev->mgmt_wq);
+	}
+
+	if (mutex_lock_interruptible(&dev->mutex)) {
+		xdev_dbg(dev, "mutex_lock_interruptible got signalled\n");
+		xshmchr_put(dev);
+		return -ERESTARTSYS;
+	}
+
+	drain_ringbuf(dev);
+
+	misc_deregister(&dev->misc);
+
+	/* Remove from list. */
+	list_del(&dev->list_field);
+
+#ifdef CONFIG_DEBUG_FS
+	if (dev->debugfs_device_dir != NULL)
+		debugfs_remove_recursive(dev->debugfs_device_dir);
+#endif
+
+	mutex_unlock(&dev->mutex);
+	xshmchr_put(dev);
+	return 0;
+}
+
+static void cfshm_remove(struct xshm_dev *xshm)
+{
+	int err;
+
+	pr_devel("unregister pdev:%s chr=%s xshm=%p\n",
+			dev_name(&xshm->dev),
+			xshm->cfg.name, xshm);
+
+	err = chrdev_remove(xshm->driver_data);
+	if (err)
+		pr_debug("removing char-dev:%s failed.%d\n",
+					xshm->cfg.name, err);
+
+	xshm->ipc_rx_cb = NULL;
+	xshm->ipc_tx_release_cb = NULL;
+	xshm->open_cb = NULL;
+	xshm->close_cb = NULL;
+	xshm->driver_data = NULL;
+}
+
+static struct xshm_driver cfshm_drv = {
+	.mode = XSHM_STREAM_MODE,
+	.probe = cfshm_probe,
+	.remove = cfshm_remove,
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.owner = THIS_MODULE,
+	},
+};
+
+
+static int __init xshmchr_chrinit_module(void)
+{
+	int err;
+	pr_devel("xshm init\n");
+	spin_lock_init(&list_lock);
+
+	/* Register xshm driver. */
+	err = xshm_register_driver(&cfshm_drv);
+	if (err) {
+		printk(KERN_ERR "Could not register SHM driver: %d.\n",
+			err);
+		goto err_dev_register;
+	}
+
+#ifdef CONFIG_DEBUG_FS
+	debugfsdir = debugfs_create_dir("xshm_chr", NULL);
+#endif
+
+ err_dev_register:
+	return err;
+
+}
+
+static void __exit xshmchr_chrexit_module(void)
+{
+	int result;
+	struct xshmchr_char_dev *dev = NULL;
+
+	/* Unregister xshm driver. */
+	xshm_unregister_driver(&cfshm_drv);
+
+	do {
+		/* Remove any device (the first in the list). */
+		dev = find_device(-1, NULL, 0);
+		result = chrdev_remove(dev);
+	} while (result == 0);
+
+#ifdef CONFIG_DEBUG_FS
+	if (debugfsdir != NULL)
+		debugfs_remove_recursive(debugfsdir);
+#endif
+
+}
+
+module_init(xshmchr_chrinit_module);
+module_exit(xshmchr_chrexit_module);
-- 
1.7.1

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