mirror of
https://github.com/torvalds/linux.git
synced 2024-09-23 08:23:44 +00:00
9e69c935fa
Since the buffer is accessed by userspace we can not just free the buffers memory once we are done with it in kernel space. There might still be open file descriptors and userspace still might be accessing the buffer. This patch adds support for reference counting to the IIO buffers. When a buffer is created and initialized its initial reference count is set to 1. Instead of freeing the memory of the buffer the buffer's _free() function will drop that reference again. But only after the last reference to the buffer has been dropped the buffer the buffer's memory will be freed. The IIO device will take a reference to its primary buffer. The patch adds a small helper function for this called iio_device_attach_buffer() which will get a reference to the buffer and assign the buffer to the IIO device. This function must be used instead of assigning the buffer to the device by hand. The reference is only dropped once the IIO device is freed and we can be sure that there are no more open file handles. A reference to a buffer will also be taken whenever the buffer is active to avoid the buffer being freed while data is still being send to it. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Jonathan Cameron <jic23@kernel.org>
114 lines
3.4 KiB
C
114 lines
3.4 KiB
C
/*
|
|
* Copyright (c) 2012 Analog Devices, Inc.
|
|
* Author: Lars-Peter Clausen <lars@metafoo.de>
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify it
|
|
* under the terms of the GNU General Public License version 2 as published by
|
|
* the Free Software Foundation.
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/module.h>
|
|
#include <linux/iio/iio.h>
|
|
#include <linux/iio/buffer.h>
|
|
#include <linux/iio/kfifo_buf.h>
|
|
#include <linux/iio/triggered_buffer.h>
|
|
#include <linux/iio/trigger_consumer.h>
|
|
|
|
static const struct iio_buffer_setup_ops iio_triggered_buffer_setup_ops = {
|
|
.preenable = &iio_sw_buffer_preenable,
|
|
.postenable = &iio_triggered_buffer_postenable,
|
|
.predisable = &iio_triggered_buffer_predisable,
|
|
};
|
|
|
|
/**
|
|
* iio_triggered_buffer_setup() - Setup triggered buffer and pollfunc
|
|
* @indio_dev: IIO device structure
|
|
* @pollfunc_bh: Function which will be used as pollfunc bottom half
|
|
* @pollfunc_th: Function which will be used as pollfunc top half
|
|
* @setup_ops: Buffer setup functions to use for this device.
|
|
* If NULL the default setup functions for triggered
|
|
* buffers will be used.
|
|
*
|
|
* This function combines some common tasks which will normally be performed
|
|
* when setting up a triggered buffer. It will allocate the buffer and the
|
|
* pollfunc, as well as register the buffer with the IIO core.
|
|
*
|
|
* Before calling this function the indio_dev structure should already be
|
|
* completely initialized, but not yet registered. In practice this means that
|
|
* this function should be called right before iio_device_register().
|
|
*
|
|
* To free the resources allocated by this function call
|
|
* iio_triggered_buffer_cleanup().
|
|
*/
|
|
int iio_triggered_buffer_setup(struct iio_dev *indio_dev,
|
|
irqreturn_t (*pollfunc_bh)(int irq, void *p),
|
|
irqreturn_t (*pollfunc_th)(int irq, void *p),
|
|
const struct iio_buffer_setup_ops *setup_ops)
|
|
{
|
|
struct iio_buffer *buffer;
|
|
int ret;
|
|
|
|
buffer = iio_kfifo_allocate(indio_dev);
|
|
if (!buffer) {
|
|
ret = -ENOMEM;
|
|
goto error_ret;
|
|
}
|
|
|
|
iio_device_attach_buffer(indio_dev, buffer);
|
|
|
|
indio_dev->pollfunc = iio_alloc_pollfunc(pollfunc_bh,
|
|
pollfunc_th,
|
|
IRQF_ONESHOT,
|
|
indio_dev,
|
|
"%s_consumer%d",
|
|
indio_dev->name,
|
|
indio_dev->id);
|
|
if (indio_dev->pollfunc == NULL) {
|
|
ret = -ENOMEM;
|
|
goto error_kfifo_free;
|
|
}
|
|
|
|
/* Ring buffer functions - here trigger setup related */
|
|
if (setup_ops)
|
|
indio_dev->setup_ops = setup_ops;
|
|
else
|
|
indio_dev->setup_ops = &iio_triggered_buffer_setup_ops;
|
|
|
|
/* Flag that polled ring buffering is possible */
|
|
indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
|
|
|
|
ret = iio_buffer_register(indio_dev,
|
|
indio_dev->channels,
|
|
indio_dev->num_channels);
|
|
if (ret)
|
|
goto error_dealloc_pollfunc;
|
|
|
|
return 0;
|
|
|
|
error_dealloc_pollfunc:
|
|
iio_dealloc_pollfunc(indio_dev->pollfunc);
|
|
error_kfifo_free:
|
|
iio_kfifo_free(indio_dev->buffer);
|
|
error_ret:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(iio_triggered_buffer_setup);
|
|
|
|
/**
|
|
* iio_triggered_buffer_cleanup() - Free resources allocated by iio_triggered_buffer_setup()
|
|
* @indio_dev: IIO device structure
|
|
*/
|
|
void iio_triggered_buffer_cleanup(struct iio_dev *indio_dev)
|
|
{
|
|
iio_buffer_unregister(indio_dev);
|
|
iio_dealloc_pollfunc(indio_dev->pollfunc);
|
|
iio_kfifo_free(indio_dev->buffer);
|
|
}
|
|
EXPORT_SYMBOL(iio_triggered_buffer_cleanup);
|
|
|
|
MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
|
|
MODULE_DESCRIPTION("IIO helper functions for setting up triggered buffers");
|
|
MODULE_LICENSE("GPL");
|