staging:iio: Drop {mark,unmark}_in_use callbacks

These callbacks are currently used by the individual buffer implementations to
ensure that the request_update callback is not issued while the buffer is in use.
But the core already provides sufficient measures to prevent this from happening
in the first place. So it is safe to remove them.

There is one functional change due to this patch. Since the buffer is no longer
marked as in use when the chrdev is opened, it is now possible to enable the
buffer while it is opened. This did not work before, because mark_param_change
did fail if the buffer was marked as in use.

Acked-by: Jonathan Cameron <[e-mail]>
Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/iio/Documentation/ring.txt

···
 as much buffer functionality as possible. Note almost all of these
 are optional.
 
-mark_in_use, unmark_in_use
-  Basically indicate that not changes should be made to the buffer state that
-  will effect the form of the data being captures (e.g. scan elements or length)
-
 store_to
   If possible, push data to the buffer.
 

drivers/staging/iio/buffer.h

···
 
 /**
  * struct iio_buffer_access_funcs - access functions for buffers.
- * @mark_in_use:	reference counting, typically to prevent module removal
- * @unmark_in_use:	reduce reference count when no longer using buffer
  * @store_to:		actually store stuff to the buffer
  * @read_first_n:	try to get a specified number of bytes (must exist)
  * @request_update:	if a parameter change has been marked, update underlying
···
  * any of them not existing.
  **/
 struct iio_buffer_access_funcs {
-	void (*mark_in_use)(struct iio_buffer *buffer);
-	void (*unmark_in_use)(struct iio_buffer *buffer);
-
 	int (*store_to)(struct iio_buffer *buffer, u8 *data, s64 timestamp);
 	int (*read_first_n)(struct iio_buffer *buffer,
 			    size_t n,

drivers/staging/iio/iio_core.h

···
 #ifdef CONFIG_IIO_BUFFER
 struct poll_table_struct;
 
-int iio_chrdev_buffer_open(struct iio_dev *indio_dev);
-void iio_chrdev_buffer_release(struct iio_dev *indio_dev);
-
 unsigned int iio_buffer_poll(struct file *filp,
 			     struct poll_table_struct *wait);
 ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
···
 #define iio_buffer_read_first_n_outer_addr (&iio_buffer_read_first_n_outer)
 
 #else
-
-static inline int iio_chrdev_buffer_open(struct iio_dev *indio_dev)
-{
-	return 0;
-}
-
-static inline void iio_chrdev_buffer_release(struct iio_dev *indio_dev)
-{}
 
 #define iio_buffer_poll_addr NULL
 #define iio_buffer_read_first_n_outer_addr NULL

drivers/staging/iio/industrialio-buffer.c

···
 	return 0;
 }
 
-int iio_chrdev_buffer_open(struct iio_dev *indio_dev)
-{
-	struct iio_buffer *rb = indio_dev->buffer;
-	if (!rb)
-		return 0;
-	if (rb->access->mark_in_use)
-		rb->access->mark_in_use(rb);
-	return 0;
-}
-
-void iio_chrdev_buffer_release(struct iio_dev *indio_dev)
-{
-	struct iio_buffer *rb = indio_dev->buffer;
-
-	if (!rb)
-		return;
-	if (rb->access->unmark_in_use)
-		rb->access->unmark_in_use(rb);
-}
-
 void iio_buffer_init(struct iio_buffer *buffer)
 {
 	INIT_LIST_HEAD(&buffer->demux_list);
···
 				goto error_ret;
 			}
 		}
-		if (buffer->access->mark_in_use)
-			buffer->access->mark_in_use(buffer);
 		/* Definitely possible for devices to support both of these.*/
 		if (indio_dev->modes & INDIO_BUFFER_TRIGGERED) {
 			if (!indio_dev->trig) {
 				printk(KERN_INFO
 				       "Buffer not started: no trigger\n");
 				ret = -EINVAL;
-				if (buffer->access->unmark_in_use)
-					buffer->access->unmark_in_use(buffer);
 				goto error_ret;
 			}
 			indio_dev->currentmode = INDIO_BUFFER_TRIGGERED;
···
 				printk(KERN_INFO
 				       "Buffer not started:"
 				       "postenable failed\n");
-				if (buffer->access->unmark_in_use)
-					buffer->access->unmark_in_use(buffer);
 				indio_dev->currentmode = previous_mode;
 				if (indio_dev->setup_ops->postdisable)
 					indio_dev->setup_ops->
···
 			if (ret)
 				goto error_ret;
 		}
-		if (buffer->access->unmark_in_use)
-			buffer->access->unmark_in_use(buffer);
 		indio_dev->currentmode = INDIO_DIRECT_MODE;
 		if (indio_dev->setup_ops->postdisable) {
 			ret = indio_dev->setup_ops->postdisable(indio_dev);

drivers/staging/iio/industrialio-core.c

···
 {
 	struct iio_dev *indio_dev = container_of(inode->i_cdev,
 						struct iio_dev, chrdev);
-	unsigned int ret;
 
 	if (test_and_set_bit(IIO_BUSY_BIT_POS, &indio_dev->flags))
 		return -EBUSY;
 
 	filp->private_data = indio_dev;
 
-	ret = iio_chrdev_buffer_open(indio_dev);
-	if (ret < 0)
-		clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
-
-	return ret;
+	return 0;
 }
 
 /**
···
 {
 	struct iio_dev *indio_dev = container_of(inode->i_cdev,
 						struct iio_dev, chrdev);
-	iio_chrdev_buffer_release(indio_dev);
 	clear_bit(IIO_BUSY_BIT_POS, &indio_dev->flags);
 	return 0;
 }

drivers/staging/iio/kfifo_buf.c

···
 struct iio_kfifo {
 	struct iio_buffer buffer;
 	struct kfifo kf;
-	int use_count;
 	int update_needed;
-	struct mutex use_lock;
 };
 
 #define iio_to_kfifo(r) container_of(r, struct iio_kfifo, buffer)
···
 	int ret = 0;
 	struct iio_kfifo *buf = iio_to_kfifo(r);
 
-	mutex_lock(&buf->use_lock);
 	if (!buf->update_needed)
 		goto error_ret;
-	if (buf->use_count) {
-		ret = -EAGAIN;
-		goto error_ret;
-	}
 	kfifo_free(&buf->kf);
 	ret = __iio_allocate_kfifo(buf, buf->buffer.bytes_per_datum,
 				   buf->buffer.length);
 error_ret:
-	mutex_unlock(&buf->use_lock);
 	return ret;
-}
-
-static void iio_mark_kfifo_in_use(struct iio_buffer *r)
-{
-	struct iio_kfifo *buf = iio_to_kfifo(r);
-	mutex_lock(&buf->use_lock);
-	buf->use_count++;
-	mutex_unlock(&buf->use_lock);
-}
-
-static void iio_unmark_kfifo_in_use(struct iio_buffer *r)
-{
-	struct iio_kfifo *buf = iio_to_kfifo(r);
-	mutex_lock(&buf->use_lock);
-	buf->use_count--;
-	mutex_unlock(&buf->use_lock);
 }
 
 static int iio_get_length_kfifo(struct iio_buffer *r)
 {
 	return r->length;
-}
-
-static inline void __iio_init_kfifo(struct iio_kfifo *kf)
-{
-	mutex_init(&kf->use_lock);
 }
 
 static IIO_BUFFER_ENABLE_ATTR;
···
 	kf->update_needed = true;
 	iio_buffer_init(&kf->buffer);
 	kf->buffer.attrs = &iio_kfifo_attribute_group;
-	__iio_init_kfifo(kf);
 
 	return &kf->buffer;
 }
···
 }
 
 const struct iio_buffer_access_funcs kfifo_access_funcs = {
-	.mark_in_use = &iio_mark_kfifo_in_use,
-	.unmark_in_use = &iio_unmark_kfifo_in_use,
 	.store_to = &iio_store_to_kfifo,
 	.read_first_n = &iio_read_first_n_kfifo,
 	.request_update = &iio_request_update_kfifo,

drivers/staging/iio/ring_sw.c

···
  * @read_p:		read pointer (oldest available)
  * @write_p:		write pointer
  * @half_p:		half buffer length behind write_p (event generation)
- * @use_count:		reference count to prevent resizing when in use
  * @update_needed:	flag to indicated change in size requested
- * @use_lock:		lock to prevent change in size when in use
  *
  * Note that the first element of all ring buffers must be a
  * struct iio_buffer.
···
 	unsigned char		*write_p;
 	/* used to act as a point at which to signal an event */
 	unsigned char		*half_p;
-	int			use_count;
 	int			update_needed;
-	spinlock_t		use_lock;
 };
 
 #define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf)
···
 	return ring->data ? 0 : -ENOMEM;
 }
 
-static inline void __iio_init_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
-{
-	spin_lock_init(&ring->use_lock);
-}
-
 static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
 {
 	kfree(ring->data);
 }
-
-static void iio_mark_sw_rb_in_use(struct iio_buffer *r)
-{
-	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
-	spin_lock(&ring->use_lock);
-	ring->use_count++;
-	spin_unlock(&ring->use_lock);
-}
-
-static void iio_unmark_sw_rb_in_use(struct iio_buffer *r)
-{
-	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
-	spin_lock(&ring->use_lock);
-	ring->use_count--;
-	spin_unlock(&ring->use_lock);
-}
-
 
 /* Ring buffer related functionality */
 /* Store to ring is typically called in the bh of a data ready interrupt handler
···
 	struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
 
 	r->stufftoread = false;
-	spin_lock(&ring->use_lock);
 	if (!ring->update_needed)
 		goto error_ret;
-	if (ring->use_count) {
-		ret = -EAGAIN;
-		goto error_ret;
-	}
 	__iio_free_sw_ring_buffer(ring);
 	ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
 					    ring->buf.length);
 error_ret:
-	spin_unlock(&ring->use_lock);
 	return ret;
 }
 
···
 	ring->update_needed = true;
 	buf = &ring->buf;
 	iio_buffer_init(buf);
-	__iio_init_sw_ring_buffer(ring);
 	buf->attrs = &iio_ring_attribute_group;
 
 	return buf;
···
 EXPORT_SYMBOL(iio_sw_rb_free);
 
 const struct iio_buffer_access_funcs ring_sw_access_funcs = {
-	.mark_in_use = &iio_mark_sw_rb_in_use,
-	.unmark_in_use = &iio_unmark_sw_rb_in_use,
 	.store_to = &iio_store_to_sw_rb,
 	.read_first_n = &iio_read_first_n_sw_rb,
 	.request_update = &iio_request_update_sw_rb,