iio:buffer: Simplify iio_buffer_is_active()

We can skip having to loop through all the device's buffers to see if a certain
buffer is active, if we let the buffer's list head point to itself when the
buffer is inactive.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 11 insertions, 20 deletions

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index e73033f3839a..96e97ad2538c 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -31,16 +31,9 @@ static const char * const iio_endian_prefix[] = {
         [IIO_LE] = "le",
 };
 
-static bool iio_buffer_is_active(struct iio_dev *indio_dev,
-                                 struct iio_buffer *buf)
+static bool iio_buffer_is_active(struct iio_buffer *buf)
 {
-        struct list_head *p;
-
-        list_for_each(p, &indio_dev->buffer_list)
-                if (p == &buf->buffer_list)
-                        return true;
-
-        return false;
+        return !list_empty(&buf->buffer_list);
 }
 
 /**
@@ -79,6 +72,7 @@ unsigned int iio_buffer_poll(struct file *filp,
 void iio_buffer_init(struct iio_buffer *buffer)
 {
         INIT_LIST_HEAD(&buffer->demux_list);
+        INIT_LIST_HEAD(&buffer->buffer_list);
         init_waitqueue_head(&buffer->pollq);
 }
 EXPORT_SYMBOL(iio_buffer_init);
@@ -146,7 +140,7 @@ static ssize_t iio_scan_el_store(struct device *dev,
         if (ret < 0)
                 return ret;
         mutex_lock(&indio_dev->mlock);
-        if (iio_buffer_is_active(indio_dev, indio_dev->buffer)) {
+        if (iio_buffer_is_active(indio_dev->buffer)) {
                 ret = -EBUSY;
                 goto error_ret;
         }
@@ -192,7 +186,7 @@ static ssize_t iio_scan_el_ts_store(struct device *dev,
                 return ret;
 
         mutex_lock(&indio_dev->mlock);
-        if (iio_buffer_is_active(indio_dev, indio_dev->buffer)) {
+        if (iio_buffer_is_active(indio_dev->buffer)) {
                 ret = -EBUSY;
                 goto error_ret;
         }
@@ -396,7 +390,7 @@ ssize_t iio_buffer_write_length(struct device *dev,
                         return len;
 
         mutex_lock(&indio_dev->mlock);
-        if (iio_buffer_is_active(indio_dev, indio_dev->buffer)) {
+        if (iio_buffer_is_active(indio_dev->buffer)) {
                 ret = -EBUSY;
         } else {
                 if (buffer->access->set_length)
@@ -414,9 +408,7 @@ ssize_t iio_buffer_show_enable(struct device *dev,
                                char *buf)
 {
         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-        return sprintf(buf, "%d\n",
-                       iio_buffer_is_active(indio_dev,
-                                            indio_dev->buffer));
+        return sprintf(buf, "%d\n", iio_buffer_is_active(indio_dev->buffer));
 }
 EXPORT_SYMBOL(iio_buffer_show_enable);
 
@@ -490,7 +482,7 @@ int iio_update_buffers(struct iio_dev *indio_dev,
                 indio_dev->active_scan_mask = NULL;
 
         if (remove_buffer)
-                list_del(&remove_buffer->buffer_list);
+                list_del_init(&remove_buffer->buffer_list);
         if (insert_buffer)
                 list_add(&insert_buffer->buffer_list, &indio_dev->buffer_list);
 
@@ -527,7 +519,7 @@ int iio_update_buffers(struct iio_dev *indio_dev,
                          * Roll back.
                          * Note can only occur when adding a buffer.
                          */
-                        list_del(&insert_buffer->buffer_list);
+                        list_del_init(&insert_buffer->buffer_list);
                         indio_dev->active_scan_mask = old_mask;
                         success = -EINVAL;
                 }
@@ -611,7 +603,7 @@ error_run_postdisable:
 error_remove_inserted:
 
         if (insert_buffer)
-                list_del(&insert_buffer->buffer_list);
+                list_del_init(&insert_buffer->buffer_list);
         indio_dev->active_scan_mask = old_mask;
         kfree(compound_mask);
 error_ret:
@@ -628,7 +620,6 @@ ssize_t iio_buffer_store_enable(struct device *dev,
         int ret;
         bool requested_state;
         struct iio_dev *indio_dev = dev_to_iio_dev(dev);
-        struct iio_buffer *pbuf = indio_dev->buffer;
         bool inlist;
 
         ret = strtobool(buf, &requested_state);
@@ -638,7 +629,7 @@ ssize_t iio_buffer_store_enable(struct device *dev,
         mutex_lock(&indio_dev->mlock);
 
         /* Find out if it is in the list */
-        inlist = iio_buffer_is_active(indio_dev, pbuf);
+        inlist = iio_buffer_is_active(indio_dev->buffer);
         /* Already in desired state */
         if (inlist == requested_state)
                 goto done;