@@ -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)
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(). This change has a small chance of breaking some userspace ABI, because it removes un-needed chardevs. While these chardevs (that are being removed) have always been unusable, it is likely that some scripts may check their existence (for whatever logic). And we also hope that before opening these chardevs, userspace would have already checked for some pre-conditions to make sure that opening these chardevs makes sense. For the most part, there is also the hope that it would be easier to change userspace code than revert this. But in the case that reverting this is required, it should be easy enough to do it. Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> --- drivers/iio/industrialio-core.c | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-)