[PATCH v3 3/5] iio: buffer: move iio buffer chrdev in industrialio-buffer.c

[Alexandru Ardelean <alexandru.ardelean@analog.com>]

This change makes the first jump to move the buffer chardev from indio_dev
to the buffer attached to indio_dev (i.e. indio_dev->buffer).

This requires that some functions that are shared between
'industrialio-core.c' & industrialio-buffer.c be re-shuffled.
The 'iio_buffer_fileops' is now moved to 'industrialio-buffer.c'. It's also
more appropriate to have it here, but the old 'legacy' iio_ioctl() must be
passed to it.

What happens now is:
* if IS_ENABLED(CONFIG_IIO_BUFFER) and 'indio_dev->buffer != NULL' the
  indio_dev->buffer->chrdev will be initialized (as the old legacy style
  chardev)
* if -ENOTSUPP is returned for either of the conditions above (not being
  met), the chardev will be created directly via 'indio_dev->chrdev', same
  as before; a new field is required now 'indio_dev->chrdev_initialized' to
  mark it true, so that 'indio_dev->chrdev' gets deleted if initialized;

'indio_dev->chrdev_initialized' is of type 'int', because recently
checkpatch complains that 'bool' types on structs can cause alignment
issues.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/iio_core.h            |  25 ++++---
 drivers/iio/industrialio-buffer.c | 119 ++++++++++++++++++++++++++++--
 drivers/iio/industrialio-core.c   |  59 ++++++++-------
 include/linux/iio/buffer_impl.h   |   7 ++
 include/linux/iio/iio.h           |   2 +
 5 files changed, 170 insertions(+), 42 deletions(-)

diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
index fd9a5f1d5e51..4bdadeac2710 100644
--- a/drivers/iio/iio_core.h
+++ b/drivers/iio/iio_core.h
@@ -40,24 +40,31 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals);
 #ifdef CONFIG_IIO_BUFFER
 struct poll_table_struct;
 
-__poll_t iio_buffer_poll(struct file *filp,
-			     struct poll_table_struct *wait);
-ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
-			      size_t n, loff_t *f_ps);
+long iio_device_event_ioctl(struct iio_dev *indio_dev, struct file *filp,
+			    unsigned int cmd, unsigned long arg);
+
+int iio_device_buffers_init(struct iio_dev *indio_dev, struct module *this_mod);
+void iio_device_buffers_uninit(struct iio_dev *indio_dev);
+
+void iio_device_buffers_put(struct iio_dev *indio_dev);
 
 int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev);
 void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev);
 
-#define iio_buffer_poll_addr (&iio_buffer_poll)
-#define iio_buffer_read_outer_addr (&iio_buffer_read_outer)
-
 void iio_disable_all_buffers(struct iio_dev *indio_dev);
 void iio_buffer_wakeup_poll(struct iio_dev *indio_dev);
 
 #else
 
-#define iio_buffer_poll_addr NULL
-#define iio_buffer_read_outer_addr NULL
+static inline int iio_device_buffers_init(struct iio_dev *indio_dev,
+					  struct module *this_mod)
+{
+	return -ENOTSUPP;
+}
+
+static inline void iio_device_buffers_uninit(struct iio_dev *indio_dev) {}
+
+static inline void iio_device_buffers_put(struct iio_dev *indio_dev) {}
 
 static inline int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
 {
diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index f9ffc7762f6c..4b5c3baadaab 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -99,11 +99,11 @@ static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
  * Return: negative values corresponding to error codes or ret != 0
  *	   for ending the reading activity
  **/
-ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
-			      size_t n, loff_t *f_ps)
+static ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
+				     size_t n, loff_t *f_ps)
 {
-	struct iio_dev *indio_dev = filp->private_data;
-	struct iio_buffer *rb = indio_dev->buffer;
+	struct iio_buffer *rb = filp->private_data;
+	struct iio_dev *indio_dev = rb->indio_dev;
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
 	size_t datum_size;
 	size_t to_wait;
@@ -165,11 +165,11 @@ ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
  * Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
  *	   or 0 for other cases
  */
-__poll_t iio_buffer_poll(struct file *filp,
+static __poll_t iio_buffer_poll(struct file *filp,
 			     struct poll_table_struct *wait)
 {
-	struct iio_dev *indio_dev = filp->private_data;
-	struct iio_buffer *rb = indio_dev->buffer;
+	struct iio_buffer *rb = filp->private_data;
+	struct iio_dev *indio_dev = rb->indio_dev;
 
 	if (!indio_dev->info || rb == NULL)
 		return 0;
@@ -180,6 +180,48 @@ __poll_t iio_buffer_poll(struct file *filp,
 	return 0;
 }
 
+/**
+ * iio_buffer_chrdev_open() - chrdev file open for buffer access
+ * @inode:	Inode structure for identifying the device in the file system
+ * @filp:	File structure for iio device used to keep and later access
+ *		private data
+ *
+ * Return: 0 on success or -EBUSY if the device is already opened
+ **/
+static int iio_buffer_chrdev_open(struct inode *inode, struct file *filp)
+{
+	struct iio_buffer *buffer = container_of(inode->i_cdev,
+						 struct iio_buffer, chrdev);
+
+	if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->file_ops_flags))
+		return -EBUSY;
+
+	iio_buffer_get(buffer);
+
+	filp->private_data = buffer;
+
+	return 0;
+}
+
+/**
+ * iio_buffer_chrdev_release() - chrdev file close for buffer access
+ * @inode:	Inode structure pointer for the char device
+ * @filp:	File structure pointer for the char device
+ *
+ * Return: 0 for successful release
+ */
+static int iio_buffer_chrdev_release(struct inode *inode, struct file *filp)
+{
+	struct iio_buffer *buffer = container_of(inode->i_cdev,
+						 struct iio_buffer, chrdev);
+
+	clear_bit(IIO_BUSY_BIT_POS, &buffer->file_ops_flags);
+
+	iio_buffer_put(buffer);
+
+	return 0;
+}
+
 /**
  * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
  * @indio_dev: The IIO device
@@ -1121,6 +1163,14 @@ void iio_disable_all_buffers(struct iio_dev *indio_dev)
 	iio_buffer_deactivate_all(indio_dev);
 }
 
+long iio_buffer_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+	struct iio_buffer *buffer = filep->private_data;
+	struct iio_dev *indio_dev = buffer->indio_dev;
+
+	return iio_device_event_ioctl(indio_dev, filep, cmd, arg);
+}
+
 static ssize_t iio_buffer_store_enable(struct device *dev,
 				       struct device_attribute *attr,
 				       const char *buf,
@@ -1356,6 +1406,61 @@ void iio_buffer_free_sysfs_and_mask(struct iio_dev *indio_dev)
 	iio_free_chan_devattr_list(&indio_dev->buffer->scan_el_dev_attr_list);
 }
 
+static const struct file_operations iio_buffer_fileops = {
+	.read = iio_buffer_read_outer,
+	.release = iio_buffer_chrdev_release,
+	.open = iio_buffer_chrdev_open,
+	.poll = iio_buffer_poll,
+	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
+	.unlocked_ioctl = iio_buffer_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+};
+
+int iio_device_buffers_init(struct iio_dev *indio_dev, struct module *this_mod)
+{
+	struct iio_buffer *buffer = indio_dev->buffer;
+	int ret;
+
+	if (!buffer)
+		return -ENOTSUPP;
+
+	cdev_init(&buffer->chrdev, &iio_buffer_fileops);
+
+	buffer->chrdev.owner = this_mod;
+
+	ret = cdev_device_add(&buffer->chrdev, &indio_dev->dev);
+	if (ret)
+		return ret;
+
+	iio_device_get(indio_dev);
+	iio_buffer_get(buffer);
+
+	return 0;
+}
+
+void iio_device_buffers_put(struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	if (!buffer)
+		return;
+
+	iio_buffer_put(buffer);
+}
+
+void iio_device_buffers_uninit(struct iio_dev *indio_dev)
+{
+	struct iio_buffer *buffer = indio_dev->buffer;
+
+	if (!buffer)
+		return;
+
+	cdev_device_del(&buffer->chrdev, &indio_dev->dev);
+	iio_buffer_put(buffer);
+	iio_device_put(indio_dev);
+}
+
 /**
  * iio_validate_scan_mask_onehot() - Validates that exactly one channel is selected
  * @indio_dev: the iio device
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index c8c074602709..2158aeab0bd2 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1475,7 +1475,7 @@ static void iio_dev_release(struct device *device)
 	iio_device_unregister_eventset(indio_dev);
 	iio_device_unregister_sysfs(indio_dev);
 
-	iio_buffer_put(indio_dev->buffer);
+	iio_device_buffers_put(indio_dev);
 
 	ida_simple_remove(&iio_ida, indio_dev->id);
 	kfree(indio_dev);
@@ -1610,7 +1610,7 @@ void devm_iio_device_free(struct device *dev, struct iio_dev *iio_dev)
 EXPORT_SYMBOL_GPL(devm_iio_device_free);
 
 /**
- * iio_chrdev_open() - chrdev file open for buffer access and ioctls
+ * iio_chrdev_open() - chrdev file open for event ioctls
  * @inode:	Inode structure for identifying the device in the file system
  * @filp:	File structure for iio device used to keep and later access
  *		private data
@@ -1633,7 +1633,7 @@ static int iio_chrdev_open(struct inode *inode, struct file *filp)
 }
 
 /**
- * iio_chrdev_release() - chrdev file close buffer access and ioctls
+ * iio_chrdev_release() - chrdev file close for event ioctls
  * @inode:	Inode structure pointer for the char device
  * @filp:	File structure pointer for the char device
  *
@@ -1649,11 +1649,9 @@ static int iio_chrdev_release(struct inode *inode, struct file *filp)
 	return 0;
 }
 
-/* Somewhat of a cross file organization violation - ioctls here are actually
- * event related */
-static long iio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+long iio_device_event_ioctl(struct iio_dev *indio_dev, struct file *filp,
+			    unsigned int cmd, unsigned long arg)
 {
-	struct iio_dev *indio_dev = filp->private_data;
 	int __user *ip = (int __user *)arg;
 	int fd;
 
@@ -1671,16 +1669,15 @@ static long iio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	return -EINVAL;
 }
 
-static const struct file_operations iio_buffer_fileops = {
-	.read = iio_buffer_read_outer_addr,
-	.release = iio_chrdev_release,
-	.open = iio_chrdev_open,
-	.poll = iio_buffer_poll_addr,
-	.owner = THIS_MODULE,
-	.llseek = noop_llseek,
-	.unlocked_ioctl = iio_ioctl,
-	.compat_ioctl = compat_ptr_ioctl,
-};
+/* Somewhat of a cross file organization violation - ioctls here are actually
+ * event related */
+static long iio_event_ioctl_wrapper(struct file *filp, unsigned int cmd,
+				    unsigned long arg)
+{
+	struct iio_dev *indio_dev = filp->private_data;
+
+	return iio_device_event_ioctl(indio_dev, filp, cmd, arg);
+}
 
 static int iio_check_unique_scan_index(struct iio_dev *indio_dev)
 {
@@ -1712,7 +1709,7 @@ static const struct file_operations iio_event_fileops = {
 	.open = iio_chrdev_open,
 	.owner = THIS_MODULE,
 	.llseek = noop_llseek,
-	.unlocked_ioctl = iio_ioctl,
+	.unlocked_ioctl = iio_event_ioctl_wrapper,
 	.compat_ioctl = compat_ptr_ioctl,
 };
 
@@ -1766,16 +1763,21 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
 		indio_dev->setup_ops == NULL)
 		indio_dev->setup_ops = &noop_ring_setup_ops;
 
-	if (indio_dev->buffer)
-		cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
-	else
+	ret = iio_device_buffers_init(indio_dev, this_mod);
+	if (ret) {
+		if (ret != -ENOTSUPP)
+			goto error_unreg_eventset;
+
 		cdev_init(&indio_dev->chrdev, &iio_event_fileops);
 
-	indio_dev->chrdev.owner = this_mod;
+		indio_dev->chrdev.owner = this_mod;
 
-	ret = cdev_device_add(&indio_dev->chrdev, &indio_dev->dev);
-	if (ret < 0)
-		goto error_unreg_eventset;
+		ret = cdev_device_add(&indio_dev->chrdev, &indio_dev->dev);
+		if (ret < 0)
+			goto error_unreg_eventset;
+
+		indio_dev->chrdev_initialized = true;
+	}
 
 	return 0;
 
@@ -1797,7 +1799,12 @@ EXPORT_SYMBOL(__iio_device_register);
  **/
 void iio_device_unregister(struct iio_dev *indio_dev)
 {
-	cdev_device_del(&indio_dev->chrdev, &indio_dev->dev);
+	if (indio_dev->chrdev_initialized)
+		cdev_device_del(&indio_dev->chrdev, &indio_dev->dev);
+
+	indio_dev->chrdev_initialized = false;
+
+	iio_device_buffers_uninit(indio_dev);
 
 	mutex_lock(&indio_dev->info_exist_lock);
 
diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
index 8fb92250a190..b4a55c3f556b 100644
--- a/include/linux/iio/buffer_impl.h
+++ b/include/linux/iio/buffer_impl.h
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _IIO_BUFFER_GENERIC_IMPL_H_
 #define _IIO_BUFFER_GENERIC_IMPL_H_
+#include <linux/cdev.h>
 #include <linux/sysfs.h>
 #include <linux/kref.h>
 
@@ -72,6 +73,12 @@ struct iio_buffer {
 	/** @indio_dev: IIO device to which this buffer belongs to. */
 	struct iio_dev *indio_dev;
 
+	/** @chrdev: associated character device. */
+	struct cdev chrdev;
+
+	/** @file_ops_flags: file ops related flags including busy flag. */
+	unsigned long file_ops_flags;
+
 	/** @length: Number of datums in buffer. */
 	unsigned int length;
 
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index e975020abaa6..e93497f483f7 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -517,6 +517,7 @@ struct iio_buffer_setup_ops {
  * @setup_ops:		[DRIVER] callbacks to call before and after buffer
  *			enable/disable
  * @chrdev:		[INTERN] associated character device
+ * @chrdev_initialized:	[INTERN] true if @chrdev device has been initialized
  * @groups:		[INTERN] attribute groups
  * @groupcounter:	[INTERN] index of next attribute group
  * @flags:		[INTERN] file ops related flags including busy flag.
@@ -560,6 +561,7 @@ struct iio_dev {
 	struct mutex			info_exist_lock;
 	const struct iio_buffer_setup_ops	*setup_ops;
 	struct cdev			chrdev;
+	int				chrdev_initialized;
 #define IIO_MAX_GROUPS 6
 	const struct attribute_group	*groups[IIO_MAX_GROUPS + 1];
 	int				groupcounter;
-- 
2.17.1