All of lore.kernel.org
 help / color / mirror / Atom feed
From: Alexandru Ardelean <alexandru.ardelean@analog.com>
To: <linux-kernel@vger.kernel.org>, <linux-iio@vger.kernel.org>
Cc: <lars@metafoo.de>, <Michael.Hennerich@analog.com>,
	<jic23@kernel.org>, <nuno.sa@analog.com>,
	<dragos.bogdan@analog.com>,
	Alexandru Ardelean <alexandru.ardelean@analog.com>
Subject: [PATCH v2 01/12] iio: core: register chardev only if needed
Date: Fri, 22 Jan 2021 17:57:54 +0200	[thread overview]
Message-ID: <20210122155805.83012-2-alexandru.ardelean@analog.com> (raw)
In-Reply-To: <20210122155805.83012-1-alexandru.ardelean@analog.com>

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@analog.com>
---
 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


  reply	other threads:[~2021-01-22 17:31 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-22 15:57 [PATCH v2 00/12] iio: core,buffer: add support for multiple IIO buffers per IIO device Alexandru Ardelean
2021-01-22 15:57 ` Alexandru Ardelean [this message]
2021-01-22 15:57 ` [PATCH v2 02/12] iio: buffer: add back-ref from iio_buffer to iio_dev Alexandru Ardelean
2021-01-22 15:57 ` [PATCH v2 03/12] iio: buffer: rework buffer & scan_elements dir creation Alexandru Ardelean
2021-01-22 15:57 ` [PATCH v2 04/12] iio: buffer: add index to the first IIO buffer dir and symlink it back Alexandru Ardelean
2021-01-22 15:57 ` [PATCH v2 05/12] iio: core: split __iio_device_attr_init() to init only the attr object Alexandru Ardelean
2021-01-22 15:57 ` [PATCH v2 06/12] iio: buffer: re-route scan_elements via it's kobj_type Alexandru Ardelean
2021-01-22 16:12   ` Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 07/12] iio: buffer: re-route core buffer attributes via it's new kobj_type Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 08/12] iio: buffer: add helper to get the IIO device to which a buffer belongs Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 09/12] iio: re-route all buffer attributes through new buffer kobj_type Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 10/12] iio: core: wrap iio device & buffer into struct for character devices Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 11/12] iio: buffer: introduce support for attaching more IIO buffers Alexandru Ardelean
2021-01-22 15:58 ` [PATCH v2 12/12] iio: buffer: add ioctl() to support opening extra buffers for IIO device Alexandru Ardelean

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210122155805.83012-2-alexandru.ardelean@analog.com \
    --to=alexandru.ardelean@analog.com \
    --cc=Michael.Hennerich@analog.com \
    --cc=dragos.bogdan@analog.com \
    --cc=jic23@kernel.org \
    --cc=lars@metafoo.de \
    --cc=linux-iio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=nuno.sa@analog.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.