Staging: most: add MOST driver's aim-cdev module

This patch adds the aim-cdev module of the MOST driver to the kernel's
driver staging area. This module is part of the MOST driver and handles
user space interaction by means of character devices.

This patch is needed in order to have access to MOST data through
character devices.
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/Kconfig

@@ -13,4 +13,6 @@ if MOST
 
 source "drivers/staging/most/mostcore/Kconfig"
 
+source "drivers/staging/most/aim-cdev/Kconfig"
+
 endif

drivers/staging/most/Makefile

 obj-$(CONFIG_MOSTCORE)	+= mostcore/
+obj-$(CONFIG_AIM_CDEV)	+= aim-cdev/

drivers/staging/most/aim-cdev/Kconfig

+#
+# MOST Cdev configuration
+#
+
+config AIM_CDEV
+	tristate "Cdev AIM"
+
+	---help---
+	  Say Y here if you want to commumicate via character devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called aim_cdev.
\ No newline at end of file

drivers/staging/most/aim-cdev/Makefile

+obj-$(CONFIG_AIM_CDEV) += aim_cdev.o
+
+aim_cdev-objs := cdev.o
+ccflags-y += -Idrivers/staging/most/mostcore/
\ No newline at end of file

drivers/staging/most/aim-cdev/cdev.c

+/*
+ * cdev.c - Application interfacing module for character devices
+ *
+ * Copyright (C) 2013-2015 Microchip Technology Germany II GmbH & Co. KG
+ *
+ * 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.
+ *
+ * This file is licensed under GPLv2.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/kfifo.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include "mostcore.h"
+
+static dev_t aim_devno;
+static struct class *aim_class;
+static struct ida minor_id;
+static unsigned int major;
+
+struct aim_channel {
+	wait_queue_head_t wq;
+	struct cdev cdev;
+	struct device *dev;
+	struct mutex io_mutex;
+	struct most_interface *iface;
+	struct most_channel_config *cfg;
+	unsigned int channel_id;
+	dev_t devno;
+	bool keep_mbo;
+	unsigned int mbo_offs;
+	struct mbo *stacked_mbo;
+	DECLARE_KFIFO_PTR(fifo, typeof(struct mbo *));
+	atomic_t access_ref;
+	struct list_head list;
+};
+#define to_channel(d) container_of(d, struct aim_channel, cdev)
+static struct list_head channel_list;
+static spinlock_t ch_list_lock;
+
+
+struct aim_channel *get_channel(struct most_interface *iface, int id)
+{
+	struct aim_channel *channel, *tmp;
+	unsigned long flags;
+	int found_channel = 0;
+
+	spin_lock_irqsave(&ch_list_lock, flags);
+	list_for_each_entry_safe(channel, tmp, &channel_list, list) {
+		if ((channel->iface == iface) && (channel->channel_id == id)) {
+			found_channel = 1;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&ch_list_lock, flags);
+	if (!found_channel)
+		return NULL;
+	return channel;
+}
+
+/**
+ * aim_open - implements the syscall to open the device
+ * @inode: inode pointer
+ * @filp: file pointer
+ *
+ * This stores the channel pointer in the private data field of
+ * the file structure and activates the channel within the core.
+ */
+static int aim_open(struct inode *inode, struct file *filp)
+{
+	struct aim_channel *channel;
+	int ret;
+
+	channel = to_channel(inode->i_cdev);
+	filp->private_data = channel;
+
+	if (((channel->cfg->direction == MOST_CH_RX) &&
+	     ((filp->f_flags & O_ACCMODE) != O_RDONLY))
+	    || ((channel->cfg->direction == MOST_CH_TX) &&
+		((filp->f_flags & O_ACCMODE) != O_WRONLY))) {
+		pr_info("WARN: Access flags mismatch\n");
+		return -EACCES;
+	}
+	if (!atomic_inc_and_test(&channel->access_ref)) {
+		pr_info("WARN: Device is busy\n");
+		atomic_dec(&channel->access_ref);
+		return -EBUSY;
+	}
+
+	ret = most_start_channel(channel->iface, channel->channel_id);
+	if (ret)
+		atomic_dec(&channel->access_ref);
+	return ret;
+}
+
+/**
+ * aim_close - implements the syscall to close the device
+ * @inode: inode pointer
+ * @filp: file pointer
+ *
+ * This stops the channel within the core.
+ */
+static int aim_close(struct inode *inode, struct file *filp)
+{
+	int ret;
+	struct mbo *mbo;
+	struct aim_channel *channel = to_channel(inode->i_cdev);
+
+	mutex_lock(&channel->io_mutex);
+	if (!channel->dev) {
+		mutex_unlock(&channel->io_mutex);
+		atomic_dec(&channel->access_ref);
+		device_destroy(aim_class, channel->devno);
+		cdev_del(&channel->cdev);
+		kfifo_free(&channel->fifo);
+		list_del(&channel->list);
+		kfree(channel);
+		ida_simple_remove(&minor_id, MINOR(channel->devno));
+		wake_up_interruptible(&channel->wq);
+		return 0;
+	}
+	mutex_unlock(&channel->io_mutex);
+
+	while (0 != kfifo_out((struct kfifo *)&channel->fifo, &mbo, 1))
+		most_put_mbo(mbo);
+	if (channel->keep_mbo == true)
+		most_put_mbo(channel->stacked_mbo);
+	ret = most_stop_channel(channel->iface, channel->channel_id);
+	atomic_dec(&channel->access_ref);
+	wake_up_interruptible(&channel->wq);
+	return ret;
+}
+
+/**
+ * aim_write - implements the syscall to write to the device
+ * @filp: file pointer
+ * @buf: pointer to user buffer
+ * @count: number of bytes to write
+ * @offset: offset from where to start writing
+ */
+static ssize_t aim_write(struct file *filp, const char __user *buf,
+			 size_t count, loff_t *offset)
+{
+	int ret, err;
+	size_t actual_len = 0;
+	size_t max_len = 0;
+	ssize_t retval;
+	struct mbo *mbo;
+	struct aim_channel *channel = filp->private_data;
+
+	mutex_lock(&channel->io_mutex);
+	if (unlikely(!channel->dev)) {
+		mutex_unlock(&channel->io_mutex);
+		return -EPIPE;
+	}
+	mutex_unlock(&channel->io_mutex);
+
+	mbo = most_get_mbo(channel->iface, channel->channel_id);
+
+	if (!mbo && channel->dev) {
+		if ((filp->f_flags & O_NONBLOCK))
+			return -EAGAIN;
+		if (wait_event_interruptible(
+			    channel->wq,
+			    (mbo = most_get_mbo(channel->iface,
+						channel->channel_id)) ||
+			    (channel->dev == NULL)))
+			return -ERESTARTSYS;
+	}
+
+	mutex_lock(&channel->io_mutex);
+	if (unlikely(!channel->dev)) {
+		mutex_unlock(&channel->io_mutex);
+		err = -EPIPE;
+		goto error;
+	}
+	mutex_unlock(&channel->io_mutex);
+
+	max_len = channel->cfg->buffer_size;
+	actual_len = min(count, max_len);
+	mbo->buffer_length = actual_len;
+
+	retval = copy_from_user(mbo->virt_address, buf, mbo->buffer_length);
+	if (retval) {
+		err = -EIO;
+		goto error;
+	}
+
+	ret = most_submit_mbo(mbo);
+	if (ret) {
+		pr_info("submitting MBO to core failed\n");
+		err = ret;
+		goto error;
+	}
+	return actual_len - retval;
+error:
+	most_put_mbo(mbo);
+	return err;
+}
+
+/**
+ * aim_read - implements the syscall to read from the device
+ * @filp: file pointer
+ * @buf: pointer to user buffer
+ * @count: number of bytes to read
+ * @offset: offset from where to start reading
+ */
+static ssize_t
+aim_read(struct file *filp, char __user *buf, size_t count, loff_t *offset)
+{
+	ssize_t retval;
+	size_t not_copied, proc_len;
+	struct mbo *mbo;
+	struct aim_channel *channel = filp->private_data;
+
+	if (channel->keep_mbo == true) {
+		mbo = channel->stacked_mbo;
+		channel->keep_mbo = false;
+		goto start_copy;
+	}
+	while ((0 == kfifo_out(&channel->fifo, &mbo, 1))
+	       && (channel->dev != NULL)) {
+		if (filp->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		if (wait_event_interruptible(channel->wq,
+					     (!kfifo_is_empty(&channel->fifo) ||
+					      (channel->dev == NULL))))
+			return -ERESTARTSYS;
+	}
+
+start_copy:
+	/* make sure we don't submit to gone devices */
+	mutex_lock(&channel->io_mutex);
+	if (unlikely(!channel->dev)) {
+		mutex_unlock(&channel->io_mutex);
+		return -EIO;
+	}
+
+	if (count < mbo->processed_length)
+		channel->keep_mbo = true;
+
+	proc_len = min((int)count,
+		       (int)(mbo->processed_length - channel->mbo_offs));
+
+	not_copied = copy_to_user(buf,
+				  mbo->virt_address + channel->mbo_offs,
+				  proc_len);
+
+	retval = not_copied ? proc_len - not_copied : proc_len;
+
+	if (channel->keep_mbo == true) {
+		channel->mbo_offs = retval;
+		channel->stacked_mbo = mbo;
+	} else {
+		most_put_mbo(mbo);
+		channel->mbo_offs = 0;
+	}
+	mutex_unlock(&channel->io_mutex);
+	return retval;
+}
+
+/**
+ * Initialization of struct file_operations
+ */
+static const struct file_operations channel_fops = {
+	.owner = THIS_MODULE,
+	.read = aim_read,
+	.write = aim_write,
+	.open = aim_open,
+	.release = aim_close,
+};
+
+/**
+ * aim_disconnect_channel - disconnect a channel
+ * @iface: pointer to interface instance
+ * @channel_id: channel index
+ *
+ * This frees allocated memory and removes the cdev that represents this
+ * channel in user space.
+ */
+int aim_disconnect_channel(struct most_interface *iface, int channel_id)
+{
+	struct aim_channel *channel;
+	unsigned long flags;
+
+	if (!iface) {
+		pr_info("Bad interface pointer\n");
+		return -EINVAL;
+	}
+
+	channel = get_channel(iface, channel_id);
+	if (channel == NULL)
+		return -ENXIO;
+
+	mutex_lock(&channel->io_mutex);
+	channel->dev = NULL;
+	mutex_unlock(&channel->io_mutex);
+
+	if (atomic_read(&channel->access_ref)) {
+		device_destroy(aim_class, channel->devno);
+		cdev_del(&channel->cdev);
+		kfifo_free(&channel->fifo);
+		ida_simple_remove(&minor_id, MINOR(channel->devno));
+		spin_lock_irqsave(&ch_list_lock, flags);
+		list_del(&channel->list);
+		spin_unlock_irqrestore(&ch_list_lock, flags);
+		kfree(channel);
+	} else {
+		wake_up_interruptible(&channel->wq);
+	}
+	return 0;
+}
+
+/**
+ * aim_rx_completion - completion handler for rx channels
+ * @mbo: pointer to buffer object that has completed
+ *
+ * This searches for the channel linked to this MBO and stores it in the local
+ * fifo buffer.
+ */
+int aim_rx_completion(struct mbo *mbo)
+{
+	struct aim_channel *channel;
+
+	if (!mbo)
+		return -EINVAL;
+
+	channel = get_channel(mbo->ifp, mbo->hdm_channel_id);
+	if (channel == NULL)
+		return -ENXIO;
+
+	kfifo_in(&channel->fifo, &mbo, 1);
+#ifdef DEBUG_MESG
+	if (kfifo_is_full(&channel->fifo))
+		pr_info("WARN: Fifo is full\n");
+#endif
+	wake_up_interruptible(&channel->wq);
+	return 0;
+}
+
+/**
+ * aim_tx_completion - completion handler for tx channels
+ * @iface: pointer to interface instance
+ * @channel_id: channel index/ID
+ *
+ * This wakes sleeping processes in the wait-queue.
+ */
+int aim_tx_completion(struct most_interface *iface, int channel_id)
+{
+	struct aim_channel *channel;
+
+	if (!iface) {
+		pr_info("Bad interface pointer\n");
+		return -EINVAL;
+	}
+	if ((channel_id < 0) || (channel_id >= iface->num_channels)) {
+		pr_info("Channel ID out of range\n");
+		return -EINVAL;
+	}
+
+	channel = get_channel(iface, channel_id);
+	if (channel == NULL)
+		return -ENXIO;
+	wake_up_interruptible(&channel->wq);
+	return 0;
+}
+
+struct most_aim cdev_aim;
+
+/**
+ * aim_probe - probe function of the driver module
+ * @iface: pointer to interface instance
+ * @channel_id: channel index/ID
+ * @cfg: pointer to actual channel configuration
+ * @parent: pointer to kobject (needed for sysfs hook-up)
+ * @name: name of the device to be created
+ *
+ * This allocates achannel object and creates the device node in /dev
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+int aim_probe(struct most_interface *iface, int channel_id,
+	      struct most_channel_config *cfg,
+	      struct kobject *parent, char *name)
+{
+	struct aim_channel *channel;
+	unsigned long cl_flags;
+	int retval;
+	int current_minor;
+
+	if ((!iface) || (!cfg) || (!parent) || (!name)) {
+		pr_info("Probing AIM with bad arguments");
+		return -EINVAL;
+	}
+	channel = get_channel(iface, channel_id);
+	if (channel)
+		return -EEXIST;
+
+	current_minor = ida_simple_get(&minor_id, 0, 0, GFP_KERNEL);
+	if (current_minor < 0)
+		return current_minor;
+
+	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
+	if (!channel) {
+		pr_info("failed to alloc channel object\n");
+		retval = -ENOMEM;
+		goto error_alloc_channel;
+	}
+
+	channel->devno = MKDEV(major, current_minor);
+	cdev_init(&channel->cdev, &channel_fops);
+	channel->cdev.owner = THIS_MODULE;
+	cdev_add(&channel->cdev, channel->devno, 1);
+	channel->iface = iface;
+	channel->cfg = cfg;
+	channel->channel_id = channel_id;
+	channel->mbo_offs = 0;
+	atomic_set(&channel->access_ref, -1);
+	INIT_KFIFO(channel->fifo);
+	retval = kfifo_alloc(&channel->fifo, cfg->num_buffers, GFP_KERNEL);
+	if (retval) {
+		pr_info("failed to alloc channel kfifo");
+		goto error_alloc_kfifo;
+	}
+	init_waitqueue_head(&channel->wq);
+	mutex_init(&channel->io_mutex);
+	spin_lock_irqsave(&ch_list_lock, cl_flags);
+	list_add_tail(&channel->list, &channel_list);
+	spin_unlock_irqrestore(&ch_list_lock, cl_flags);
+	channel->dev = device_create(aim_class,
+				     NULL,
+				     channel->devno,
+				     NULL,
+				     "%s", name);
+
+	retval = IS_ERR(channel->dev);
+	if (retval) {
+		pr_info("failed to create new device node %s\n", name);
+		goto error_create_device;
+	}
+	kobject_uevent(&channel->dev->kobj, KOBJ_ADD);
+	return 0;
+
+error_create_device:
+	kfifo_free(&channel->fifo);
+	list_del(&channel->list);
+error_alloc_kfifo:
+	cdev_del(&channel->cdev);
+	kfree(channel);
+error_alloc_channel:
+	ida_simple_remove(&minor_id, current_minor);
+	return retval;
+}
+
+struct most_aim cdev_aim = {
+	.name = "cdev",
+	.probe_channel = aim_probe,
+	.disconnect_channel = aim_disconnect_channel,
+	.rx_completion = aim_rx_completion,
+	.tx_completion = aim_tx_completion,
+};
+
+static int __init mod_init(void)
+{
+	pr_info("init()\n");
+
+	INIT_LIST_HEAD(&channel_list);
+	spin_lock_init(&ch_list_lock);
+	ida_init(&minor_id);
+
+	if (alloc_chrdev_region(&aim_devno, 0, 50, "cdev") < 0)
+		return -EIO;
+	major = MAJOR(aim_devno);
+
+	aim_class = class_create(THIS_MODULE, "most_cdev_aim");
+	if (IS_ERR(aim_class)) {
+		pr_err("no udev support\n");
+		goto free_cdev;
+	}
+
+	if (most_register_aim(&cdev_aim))
+		goto dest_class;
+	return 0;
+
+dest_class:
+	class_destroy(aim_class);
+free_cdev:
+	unregister_chrdev_region(aim_devno, 1);
+	return -EIO;
+}
+
+static void __exit mod_exit(void)
+{
+	struct aim_channel *channel, *tmp;
+
+	pr_info("exit module\n");
+
+	most_deregister_aim(&cdev_aim);
+
+	list_for_each_entry_safe(channel, tmp, &channel_list, list) {
+		device_destroy(aim_class, channel->devno);
+		cdev_del(&channel->cdev);
+		kfifo_free(&channel->fifo);
+		list_del(&channel->list);
+		ida_simple_remove(&minor_id, MINOR(channel->devno));
+		kfree(channel);
+	}
+	class_destroy(aim_class);
+	unregister_chrdev_region(aim_devno, 1);
+	ida_destroy(&minor_id);
+}
+
+module_init(mod_init);
+module_exit(mod_exit);
+MODULE_AUTHOR("Christian Gromm <christian.gromm@microchip.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("character device AIM for mostcore");