We only need a chardev if we need to support buffers and/or events.
With this change, a chardev will be created only if an IIO buffer is
attached OR an event_interface is configured.
Otherwise, no chardev will be created, and the IIO device will get
registered with the 'device_add()' call.
Quite a lot of IIO devices don't really need a chardev, so this is a minor
improvement to the IIO core, as the IIO device will take up (slightly)
fewer resources.
In order to not create a chardev, we mostly just need to not initialize the
indio_dev->dev.devt field. If that is un-initialized, cdev_device_add()
behaves like device_add().
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
---
drivers/iio/industrialio-core.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 7db761afa578..0a6fd299a978 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -1761,6 +1761,15 @@ static const struct file_operations iio_buffer_fileops = {
.release = iio_chrdev_release,
};
+static const struct file_operations iio_event_fileops = {
+ .owner = THIS_MODULE,
+ .llseek = noop_llseek,
+ .unlocked_ioctl = iio_ioctl,
+ .compat_ioctl = compat_ptr_ioctl,
+ .open = iio_chrdev_open,
+ .release = iio_chrdev_release,
+};
+
static int iio_check_unique_scan_index(struct iio_dev *indio_dev)
{
int i, j;
@@ -1788,6 +1797,7 @@ static const struct iio_buffer_setup_ops noop_ring_setup_ops;
int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
{
+ struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
int ret;
if (!indio_dev->info)
@@ -1805,9 +1815,6 @@ int __iio_device_register(struct iio_dev *indio_dev, struct module *this_mod)
if (ret < 0)
return ret;
- /* configure elements for the chrdev */
- indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), indio_dev->id);
-
iio_device_register_debugfs(indio_dev);
ret = iio_buffer_alloc_sysfs_and_mask(indio_dev);
@@ -1836,9 +1843,15 @@ 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;
- cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
+ if (indio_dev->buffer)
+ cdev_init(&indio_dev->chrdev, &iio_buffer_fileops);
+ else if (iio_dev_opaque->event_interface)
+ cdev_init(&indio_dev->chrdev, &iio_event_fileops);
- indio_dev->chrdev.owner = this_mod;
+ if (indio_dev->buffer || iio_dev_opaque->event_interface) {
+ indio_dev->dev.devt = MKDEV(MAJOR(iio_devt), indio_dev->id);
+ indio_dev->chrdev.owner = this_mod;
+ }
ret = cdev_device_add(&indio_dev->chrdev, &indio_dev->dev);
if (ret < 0)
--
2.17.1
