drivers: most: add character device interface driver

This patch adds the character device (cdev) driver source file
most_cdev.c and modifies the Makefiles and Kconfigs accordingly.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Link: https://lore.kernel.org/r/1597922595-27493-1-git-send-email-christian.gromm@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 553 insertions, 0 deletions

diff --git a/drivers/most/Kconfig b/drivers/most/Kconfig
index 60fc0820dad3..ebfe84e69715 100644
--- a/drivers/most/Kconfig
+++ b/drivers/most/Kconfig
@@ -23,4 +23,13 @@ config MOST_USB_HDM
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called most_usb.
+
+config MOST_CDEV
+	tristate "Cdev"
+
+	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 most_cdev.
 endif
diff --git a/drivers/most/Makefile b/drivers/most/Makefile
index 6a3cb9056288..8b53ca46633f 100644
--- a/drivers/most/Makefile
+++ b/drivers/most/Makefile
@@ -4,3 +4,4 @@ most_core-y :=	core.o \
 		configfs.o
 
 obj-$(CONFIG_MOST_USB_HDM) += most_usb.o
+obj-$(CONFIG_MOST_CDEV) += most_cdev.o
diff --git a/drivers/most/most_cdev.c b/drivers/most/most_cdev.c
new file mode 100644
index 000000000000..044880760b58
--- /dev/null
+++ b/drivers/most/most_cdev.c
@@ -0,0 +1,543 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * cdev.c - Character device component for Mostcore
+ *
+ * Copyright (C) 2013-2015 Microchip Technology Germany II GmbH & Co. KG
+ */
+
+#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/poll.h>
+#include <linux/kfifo.h>
+#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/most.h>
+
+#define CHRDEV_REGION_SIZE 50
+
+static struct cdev_component {
+	dev_t devno;
+	struct ida minor_id;
+	unsigned int major;
+	struct class *class;
+	struct most_component cc;
+} comp;
+
+struct comp_channel {
+	wait_queue_head_t wq;
+	spinlock_t unlink;	/* synchronization lock to unlink channels */
+	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;
+	size_t mbo_offs;
+	DECLARE_KFIFO_PTR(fifo, typeof(struct mbo *));
+	int access_ref;
+	struct list_head list;
+};
+
+#define to_channel(d) container_of(d, struct comp_channel, cdev)
+static struct list_head channel_list;
+static spinlock_t ch_list_lock;
+
+static inline bool ch_has_mbo(struct comp_channel *c)
+{
+	return channel_has_mbo(c->iface, c->channel_id, &comp.cc) > 0;
+}
+
+static inline struct mbo *ch_get_mbo(struct comp_channel *c, struct mbo **mbo)
+{
+	if (!kfifo_peek(&c->fifo, mbo)) {
+		*mbo = most_get_mbo(c->iface, c->channel_id, &comp.cc);
+		if (*mbo)
+			kfifo_in(&c->fifo, mbo, 1);
+	}
+	return *mbo;
+}
+
+static struct comp_channel *get_channel(struct most_interface *iface, int id)
+{
+	struct comp_channel *c, *tmp;
+	unsigned long flags;
+
+	spin_lock_irqsave(&ch_list_lock, flags);
+	list_for_each_entry_safe(c, tmp, &channel_list, list) {
+		if ((c->iface == iface) && (c->channel_id == id)) {
+			spin_unlock_irqrestore(&ch_list_lock, flags);
+			return c;
+		}
+	}
+	spin_unlock_irqrestore(&ch_list_lock, flags);
+	return NULL;
+}
+
+static void stop_channel(struct comp_channel *c)
+{
+	struct mbo *mbo;
+
+	while (kfifo_out((struct kfifo *)&c->fifo, &mbo, 1))
+		most_put_mbo(mbo);
+	most_stop_channel(c->iface, c->channel_id, &comp.cc);
+}
+
+static void destroy_cdev(struct comp_channel *c)
+{
+	unsigned long flags;
+
+	device_destroy(comp.class, c->devno);
+	cdev_del(&c->cdev);
+	spin_lock_irqsave(&ch_list_lock, flags);
+	list_del(&c->list);
+	spin_unlock_irqrestore(&ch_list_lock, flags);
+}
+
+static void destroy_channel(struct comp_channel *c)
+{
+	ida_simple_remove(&comp.minor_id, MINOR(c->devno));
+	kfifo_free(&c->fifo);
+	kfree(c);
+}
+
+/**
+ * comp_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 comp_open(struct inode *inode, struct file *filp)
+{
+	struct comp_channel *c;
+	int ret;
+
+	c = to_channel(inode->i_cdev);
+	filp->private_data = c;
+
+	if (((c->cfg->direction == MOST_CH_RX) &&
+	     ((filp->f_flags & O_ACCMODE) != O_RDONLY)) ||
+	     ((c->cfg->direction == MOST_CH_TX) &&
+		((filp->f_flags & O_ACCMODE) != O_WRONLY))) {
+		return -EACCES;
+	}
+
+	mutex_lock(&c->io_mutex);
+	if (!c->dev) {
+		mutex_unlock(&c->io_mutex);
+		return -ENODEV;
+	}
+
+	if (c->access_ref) {
+		mutex_unlock(&c->io_mutex);
+		return -EBUSY;
+	}
+
+	c->mbo_offs = 0;
+	ret = most_start_channel(c->iface, c->channel_id, &comp.cc);
+	if (!ret)
+		c->access_ref = 1;
+	mutex_unlock(&c->io_mutex);
+	return ret;
+}
+
+/**
+ * comp_close - implements the syscall to close the device
+ * @inode: inode pointer
+ * @filp: file pointer
+ *
+ * This stops the channel within the core.
+ */
+static int comp_close(struct inode *inode, struct file *filp)
+{
+	struct comp_channel *c = to_channel(inode->i_cdev);
+
+	mutex_lock(&c->io_mutex);
+	spin_lock(&c->unlink);
+	c->access_ref = 0;
+	spin_unlock(&c->unlink);
+	if (c->dev) {
+		stop_channel(c);
+		mutex_unlock(&c->io_mutex);
+	} else {
+		mutex_unlock(&c->io_mutex);
+		destroy_channel(c);
+	}
+	return 0;
+}
+
+/**
+ * comp_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 comp_write(struct file *filp, const char __user *buf,
+			  size_t count, loff_t *offset)
+{
+	int ret;
+	size_t to_copy, left;
+	struct mbo *mbo = NULL;
+	struct comp_channel *c = filp->private_data;
+
+	mutex_lock(&c->io_mutex);
+	while (c->dev && !ch_get_mbo(c, &mbo)) {
+		mutex_unlock(&c->io_mutex);
+
+		if ((filp->f_flags & O_NONBLOCK))
+			return -EAGAIN;
+		if (wait_event_interruptible(c->wq, ch_has_mbo(c) || !c->dev))
+			return -ERESTARTSYS;
+		mutex_lock(&c->io_mutex);
+	}
+
+	if (unlikely(!c->dev)) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+
+	to_copy = min(count, c->cfg->buffer_size - c->mbo_offs);
+	left = copy_from_user(mbo->virt_address + c->mbo_offs, buf, to_copy);
+	if (left == to_copy) {
+		ret = -EFAULT;
+		goto unlock;
+	}
+
+	c->mbo_offs += to_copy - left;
+	if (c->mbo_offs >= c->cfg->buffer_size ||
+	    c->cfg->data_type == MOST_CH_CONTROL ||
+	    c->cfg->data_type == MOST_CH_ASYNC) {
+		kfifo_skip(&c->fifo);
+		mbo->buffer_length = c->mbo_offs;
+		c->mbo_offs = 0;
+		most_submit_mbo(mbo);
+	}
+
+	ret = to_copy - left;
+unlock:
+	mutex_unlock(&c->io_mutex);
+	return ret;
+}
+
+/**
+ * comp_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
+comp_read(struct file *filp, char __user *buf, size_t count, loff_t *offset)
+{
+	size_t to_copy, not_copied, copied;
+	struct mbo *mbo = NULL;
+	struct comp_channel *c = filp->private_data;
+
+	mutex_lock(&c->io_mutex);
+	while (c->dev && !kfifo_peek(&c->fifo, &mbo)) {
+		mutex_unlock(&c->io_mutex);
+		if (filp->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+		if (wait_event_interruptible(c->wq,
+					     (!kfifo_is_empty(&c->fifo) ||
+					      (!c->dev))))
+			return -ERESTARTSYS;
+		mutex_lock(&c->io_mutex);
+	}
+
+	/* make sure we don't submit to gone devices */
+	if (unlikely(!c->dev)) {
+		mutex_unlock(&c->io_mutex);
+		return -ENODEV;
+	}
+
+	to_copy = min_t(size_t,
+			count,
+			mbo->processed_length - c->mbo_offs);
+
+	not_copied = copy_to_user(buf,
+				  mbo->virt_address + c->mbo_offs,
+				  to_copy);
+
+	copied = to_copy - not_copied;
+
+	c->mbo_offs += copied;
+	if (c->mbo_offs >= mbo->processed_length) {
+		kfifo_skip(&c->fifo);
+		most_put_mbo(mbo);
+		c->mbo_offs = 0;
+	}
+	mutex_unlock(&c->io_mutex);
+	return copied;
+}
+
+static __poll_t comp_poll(struct file *filp, poll_table *wait)
+{
+	struct comp_channel *c = filp->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(filp, &c->wq, wait);
+
+	mutex_lock(&c->io_mutex);
+	if (c->cfg->direction == MOST_CH_RX) {
+		if (!c->dev || !kfifo_is_empty(&c->fifo))
+			mask |= EPOLLIN | EPOLLRDNORM;
+	} else {
+		if (!c->dev || !kfifo_is_empty(&c->fifo) || ch_has_mbo(c))
+			mask |= EPOLLOUT | EPOLLWRNORM;
+	}
+	mutex_unlock(&c->io_mutex);
+	return mask;
+}
+
+/**
+ * Initialization of struct file_operations
+ */
+static const struct file_operations channel_fops = {
+	.owner = THIS_MODULE,
+	.read = comp_read,
+	.write = comp_write,
+	.open = comp_open,
+	.release = comp_close,
+	.poll = comp_poll,
+};
+
+/**
+ * comp_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.
+ */
+static int comp_disconnect_channel(struct most_interface *iface, int channel_id)
+{
+	struct comp_channel *c;
+
+	c = get_channel(iface, channel_id);
+	if (!c)
+		return -EINVAL;
+
+	mutex_lock(&c->io_mutex);
+	spin_lock(&c->unlink);
+	c->dev = NULL;
+	spin_unlock(&c->unlink);
+	destroy_cdev(c);
+	if (c->access_ref) {
+		stop_channel(c);
+		wake_up_interruptible(&c->wq);
+		mutex_unlock(&c->io_mutex);
+	} else {
+		mutex_unlock(&c->io_mutex);
+		destroy_channel(c);
+	}
+	return 0;
+}
+
+/**
+ * comp_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.
+ */
+static int comp_rx_completion(struct mbo *mbo)
+{
+	struct comp_channel *c;
+
+	if (!mbo)
+		return -EINVAL;
+
+	c = get_channel(mbo->ifp, mbo->hdm_channel_id);
+	if (!c)
+		return -EINVAL;
+
+	spin_lock(&c->unlink);
+	if (!c->access_ref || !c->dev) {
+		spin_unlock(&c->unlink);
+		return -ENODEV;
+	}
+	kfifo_in(&c->fifo, &mbo, 1);
+	spin_unlock(&c->unlink);
+#ifdef DEBUG_MESG
+	if (kfifo_is_full(&c->fifo))
+		dev_warn(c->dev, "Fifo is full\n");
+#endif
+	wake_up_interruptible(&c->wq);
+	return 0;
+}
+
+/**
+ * comp_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.
+ */
+static int comp_tx_completion(struct most_interface *iface, int channel_id)
+{
+	struct comp_channel *c;
+
+	c = get_channel(iface, channel_id);
+	if (!c)
+		return -EINVAL;
+
+	if ((channel_id < 0) || (channel_id >= iface->num_channels)) {
+		dev_warn(c->dev, "Channel ID out of range\n");
+		return -EINVAL;
+	}
+
+	wake_up_interruptible(&c->wq);
+	return 0;
+}
+
+/**
+ * comp_probe - probe function of the driver module
+ * @iface: pointer to interface instance
+ * @channel_id: channel index/ID
+ * @cfg: pointer to actual channel configuration
+ * @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.
+ */
+static int comp_probe(struct most_interface *iface, int channel_id,
+		      struct most_channel_config *cfg, char *name, char *args)
+{
+	struct comp_channel *c;
+	unsigned long cl_flags;
+	int retval;
+	int current_minor;
+
+	if (!cfg || !name)
+		return -EINVAL;
+
+	c = get_channel(iface, channel_id);
+	if (c)
+		return -EEXIST;
+
+	current_minor = ida_simple_get(&comp.minor_id, 0, 0, GFP_KERNEL);
+	if (current_minor < 0)
+		return current_minor;
+
+	c = kzalloc(sizeof(*c), GFP_KERNEL);
+	if (!c) {
+		retval = -ENOMEM;
+		goto err_remove_ida;
+	}
+
+	c->devno = MKDEV(comp.major, current_minor);
+	cdev_init(&c->cdev, &channel_fops);
+	c->cdev.owner = THIS_MODULE;
+	retval = cdev_add(&c->cdev, c->devno, 1);
+	if (retval < 0)
+		goto err_free_c;
+	c->iface = iface;
+	c->cfg = cfg;
+	c->channel_id = channel_id;
+	c->access_ref = 0;
+	spin_lock_init(&c->unlink);
+	INIT_KFIFO(c->fifo);
+	retval = kfifo_alloc(&c->fifo, cfg->num_buffers, GFP_KERNEL);
+	if (retval)
+		goto err_del_cdev_and_free_channel;
+	init_waitqueue_head(&c->wq);
+	mutex_init(&c->io_mutex);
+	spin_lock_irqsave(&ch_list_lock, cl_flags);
+	list_add_tail(&c->list, &channel_list);
+	spin_unlock_irqrestore(&ch_list_lock, cl_flags);
+	c->dev = device_create(comp.class, NULL, c->devno, NULL, "%s", name);
+
+	if (IS_ERR(c->dev)) {
+		retval = PTR_ERR(c->dev);
+		goto err_free_kfifo_and_del_list;
+	}
+	kobject_uevent(&c->dev->kobj, KOBJ_ADD);
+	return 0;
+
+err_free_kfifo_and_del_list:
+	kfifo_free(&c->fifo);
+	list_del(&c->list);
+err_del_cdev_and_free_channel:
+	cdev_del(&c->cdev);
+err_free_c:
+	kfree(c);
+err_remove_ida:
+	ida_simple_remove(&comp.minor_id, current_minor);
+	return retval;
+}
+
+static struct cdev_component comp = {
+	.cc = {
+		.mod = THIS_MODULE,
+		.name = "cdev",
+		.probe_channel = comp_probe,
+		.disconnect_channel = comp_disconnect_channel,
+		.rx_completion = comp_rx_completion,
+		.tx_completion = comp_tx_completion,
+	},
+};
+
+static int __init mod_init(void)
+{
+	int err;
+
+	comp.class = class_create(THIS_MODULE, "most_cdev");
+	if (IS_ERR(comp.class))
+		return PTR_ERR(comp.class);
+
+	INIT_LIST_HEAD(&channel_list);
+	spin_lock_init(&ch_list_lock);
+	ida_init(&comp.minor_id);
+
+	err = alloc_chrdev_region(&comp.devno, 0, CHRDEV_REGION_SIZE, "cdev");
+	if (err < 0)
+		goto dest_ida;
+	comp.major = MAJOR(comp.devno);
+	err = most_register_component(&comp.cc);
+	if (err)
+		goto free_cdev;
+	err = most_register_configfs_subsys(&comp.cc);
+	if (err)
+		goto deregister_comp;
+	return 0;
+
+deregister_comp:
+	most_deregister_component(&comp.cc);
+free_cdev:
+	unregister_chrdev_region(comp.devno, CHRDEV_REGION_SIZE);
+dest_ida:
+	ida_destroy(&comp.minor_id);
+	class_destroy(comp.class);
+	return err;
+}
+
+static void __exit mod_exit(void)
+{
+	struct comp_channel *c, *tmp;
+
+	most_deregister_configfs_subsys(&comp.cc);
+	most_deregister_component(&comp.cc);
+
+	list_for_each_entry_safe(c, tmp, &channel_list, list) {
+		destroy_cdev(c);
+		destroy_channel(c);
+	}
+	unregister_chrdev_region(comp.devno, CHRDEV_REGION_SIZE);
+	ida_destroy(&comp.minor_id);
+	class_destroy(comp.class);
+}
+
+module_init(mod_init);
+module_exit(mod_exit);
+MODULE_AUTHOR("Christian Gromm <christian.gromm@microchip.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("character device component for mostcore");