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platform_kernel-5.15
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iio: buffer: add ioctl() to support opening extra buffers for IIO device 

With this change, an ioctl() call is added to open a character device for a
buffer. The ioctl() number is 'i' 0x91, which follows the
IIO_GET_EVENT_FD_IOCTL ioctl.

The ioctl() will return an FD for the requested buffer index. The indexes
are the same from the /sys/iio/devices/iio:deviceX/bufferY (i.e. the Y
variable).

Since there doesn't seem to be a sane way to return the FD for buffer0 to
be the same FD for the /dev/iio:deviceX, this ioctl() will return another
FD for buffer0 (or the first buffer). This duplicate FD will be able to
access the same buffer object (for buffer0) as accessing directly the
/dev/iio:deviceX chardev.

Also, there is no IIO_BUFFER_GET_BUFFER_COUNT ioctl() implemented, as the
index for each buffer (and the count) can be deduced from the
'/sys/bus/iio/devices/iio:deviceX/bufferY' folders (i.e the number of
bufferY folders).

Used following C code to test this:
-------------------------------------------------------------------

 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
 #include <fcntl.h"
 #include <errno.h>

 #define IIO_BUFFER_GET_FD_IOCTL      _IOWR('i', 0x91, int)

int main(int argc, char *argv[])
{
        int fd;
        int fd1;
        int ret;

        if ((fd = open("/dev/iio:device0", O_RDWR))<0) {
                fprintf(stderr, "Error open() %d errno %d\n",fd, errno);
                return -1;
        }

        fprintf(stderr, "Using FD %d\n", fd);

        fd1 = atoi(argv[1]);

        ret = ioctl(fd, IIO_BUFFER_GET_FD_IOCTL, &fd1);
        if (ret < 0) {
                fprintf(stderr, "Error for buffer %d ioctl() %d errno %d\n", fd1, ret, errno);
                close(fd);
                return -1;
        }

        fprintf(stderr, "Got FD %d\n", fd1);

        close(fd1);
        close(fd);

        return 0;
}
-------------------------------------------------------------------

Results are:
-------------------------------------------------------------------
 # ./test 0
 Using FD 3
 Got FD 4

 # ./test 1
 Using FD 3
 Got FD 4

 # ./test 2
 Using FD 3
 Got FD 4

 # ./test 3
 Using FD 3
 Got FD 4

 # ls /sys/bus/iio/devices/iio\:device0
 buffer  buffer0  buffer1  buffer2  buffer3  dev
 in_voltage_sampling_frequency  in_voltage_scale
 in_voltage_scale_available
 name  of_node  power  scan_elements  subsystem  uevent
-------------------------------------------------------------------

iio:device0 has some fake kfifo buffers attached to an IIO device.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-21-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Alexandru Ardelean 2021-02-15 12:40:39 +02:00 committed by Jonathan Cameron
parent ee708e6baa
commit f73f7f4da5
5 changed files with 162 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/iio/iio_core.h
View File

@ -64,16 +64,16 @@ ssize_t iio_format_value(char *buf, unsigned int type, int size, int *vals);
#ifdef CONFIG_IIO_BUFFER
struct poll_table_struct;
__poll_t iio_buffer_poll(struct file *filp,
struct poll_table_struct *wait);
ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
size_t n, loff_t *f_ps);
__poll_t iio_buffer_poll_wrapper(struct file *filp,
struct poll_table_struct *wait);
ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
size_t n, loff_t *f_ps);
int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev);
void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev);
#define iio_buffer_poll_addr (&iio_buffer_poll)
#define iio_buffer_read_outer_addr (&iio_buffer_read_outer)
#define iio_buffer_poll_addr (&iio_buffer_poll_wrapper)
#define iio_buffer_read_outer_addr (&iio_buffer_read_wrapper)
void iio_disable_all_buffers(struct iio_dev *indio_dev);
void iio_buffer_wakeup_poll(struct iio_dev *indio_dev);

144
drivers/iio/industrialio-buffer.c
View File

@ -9,9 +9,11 @@
* - Better memory allocation techniques?
* - Alternative access techniques?
*/
#include <linux/anon_inodes.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/device.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/slab.h>
@ -89,7 +91,7 @@ static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
}
/**
* iio_buffer_read_outer() - chrdev read for buffer access
* iio_buffer_read() - chrdev read for buffer access
* @filp: File structure pointer for the char device
* @buf: Destination buffer for iio buffer read
* @n: First n bytes to read
@ -101,8 +103,8 @@ static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf,
* Return: negative values corresponding to error codes or ret != 0
* for ending the reading activity
**/
ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
size_t n, loff_t *f_ps)
static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
size_t n, loff_t *f_ps)
{
struct iio_dev_buffer_pair *ib = filp->private_data;
struct iio_buffer *rb = ib->buffer;
@ -168,8 +170,8 @@ ssize_t iio_buffer_read_outer(struct file *filp, char __user *buf,
* Return: (EPOLLIN | EPOLLRDNORM) if data is available for reading
* or 0 for other cases
*/
__poll_t iio_buffer_poll(struct file *filp,
struct poll_table_struct *wait)
static __poll_t iio_buffer_poll(struct file *filp,
struct poll_table_struct *wait)
{
struct iio_dev_buffer_pair *ib = filp->private_data;
struct iio_buffer *rb = ib->buffer;
@ -184,6 +186,32 @@ __poll_t iio_buffer_poll(struct file *filp,
return 0;
}
ssize_t iio_buffer_read_wrapper(struct file *filp, char __user *buf,
size_t n, loff_t *f_ps)
{
struct iio_dev_buffer_pair *ib = filp->private_data;
struct iio_buffer *rb = ib->buffer;
/* check if buffer was opened through new API */
if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
return -EBUSY;
return iio_buffer_read(filp, buf, n, f_ps);
}
__poll_t iio_buffer_poll_wrapper(struct file *filp,
struct poll_table_struct *wait)
{
struct iio_dev_buffer_pair *ib = filp->private_data;
struct iio_buffer *rb = ib->buffer;
/* check if buffer was opened through new API */
if (test_bit(IIO_BUSY_BIT_POS, &rb->flags))
return 0;
return iio_buffer_poll(filp, wait);
}
/**
* iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
* @indio_dev: The IIO device
@ -1344,6 +1372,96 @@ static void iio_buffer_unregister_legacy_sysfs_groups(struct iio_dev *indio_dev)
kfree(iio_dev_opaque->legacy_scan_el_group.attrs);
}
static int iio_buffer_chrdev_release(struct inode *inode, struct file *filep)
{
struct iio_dev_buffer_pair *ib = filep->private_data;
struct iio_dev *indio_dev = ib->indio_dev;
struct iio_buffer *buffer = ib->buffer;
wake_up(&buffer->pollq);
kfree(ib);
clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
iio_device_put(indio_dev);
return 0;
}
static const struct file_operations iio_buffer_chrdev_fileops = {
.owner = THIS_MODULE,
.llseek = noop_llseek,
.read = iio_buffer_read,
.poll = iio_buffer_poll,
.release = iio_buffer_chrdev_release,
};
static long iio_device_buffer_getfd(struct iio_dev *indio_dev, unsigned long arg)
{
struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
int __user *ival = (int __user *)arg;
struct iio_dev_buffer_pair *ib;
struct iio_buffer *buffer;
int fd, idx, ret;
if (copy_from_user(&idx, ival, sizeof(idx)))
return -EFAULT;
if (idx >= iio_dev_opaque->attached_buffers_cnt)
return -ENODEV;
iio_device_get(indio_dev);
buffer = iio_dev_opaque->attached_buffers[idx];
if (test_and_set_bit(IIO_BUSY_BIT_POS, &buffer->flags)) {
ret = -EBUSY;
goto error_iio_dev_put;
}
ib = kzalloc(sizeof(*ib), GFP_KERNEL);
if (!ib) {
ret = -ENOMEM;
goto error_clear_busy_bit;
}
ib->indio_dev = indio_dev;
ib->buffer = buffer;
fd = anon_inode_getfd("iio:buffer", &iio_buffer_chrdev_fileops,
ib, O_RDWR | O_CLOEXEC);
if (fd < 0) {
ret = fd;
goto error_free_ib;
}
if (copy_to_user(ival, &fd, sizeof(fd))) {
put_unused_fd(fd);
ret = -EFAULT;
goto error_free_ib;
}
return fd;
error_free_ib:
kfree(ib);
error_clear_busy_bit:
clear_bit(IIO_BUSY_BIT_POS, &buffer->flags);
error_iio_dev_put:
iio_device_put(indio_dev);
return ret;
}
static long iio_device_buffer_ioctl(struct iio_dev *indio_dev, struct file *filp,
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
case IIO_BUFFER_GET_FD_IOCTL:
return iio_device_buffer_getfd(indio_dev, arg);
default:
return IIO_IOCTL_UNHANDLED;
}
}
static int __iio_buffer_alloc_sysfs_and_mask(struct iio_buffer *buffer,
struct iio_dev *indio_dev,
int index)
@ -1473,6 +1591,7 @@ int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
struct iio_buffer *buffer;
int unwind_idx;
int ret, i;
size_t sz;
channels = indio_dev->channels;
if (channels) {
@ -1494,6 +1613,18 @@ int iio_buffers_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
goto error_unwind_sysfs_and_mask;
}
}
unwind_idx = iio_dev_opaque->attached_buffers_cnt - 1;
sz = sizeof(*(iio_dev_opaque->buffer_ioctl_handler));
iio_dev_opaque->buffer_ioctl_handler = kzalloc(sz, GFP_KERNEL);
if (!iio_dev_opaque->buffer_ioctl_handler) {
ret = -ENOMEM;
goto error_unwind_sysfs_and_mask;
}
iio_dev_opaque->buffer_ioctl_handler->ioctl = iio_device_buffer_ioctl;
iio_device_ioctl_handler_register(indio_dev,
iio_dev_opaque->buffer_ioctl_handler);
return 0;
@ -1515,6 +1646,9 @@ void iio_buffers_free_sysfs_and_mask(struct iio_dev *indio_dev)
if (!iio_dev_opaque->attached_buffers_cnt)
return;
iio_device_ioctl_handler_unregister(iio_dev_opaque->buffer_ioctl_handler);
kfree(iio_dev_opaque->buffer_ioctl_handler);
iio_buffer_unregister_legacy_sysfs_groups(indio_dev);
for (i = iio_dev_opaque->attached_buffers_cnt - 1; i >= 0; i--) {

5
include/linux/iio/buffer_impl.h
View File

@ -6,6 +6,8 @@
#ifdef CONFIG_IIO_BUFFER
#include <uapi/linux/iio/buffer.h>
struct iio_dev;
struct iio_buffer;
@ -72,6 +74,9 @@ struct iio_buffer {
/** @length: Number of datums in buffer. */
unsigned int length;
/** @flags: File ops flags including busy flag. */
unsigned long flags;
/** @bytes_per_datum: Size of individual datum including timestamp. */
size_t bytes_per_datum;

2
include/linux/iio/iio-opaque.h
View File

@ -9,6 +9,7 @@
* @event_interface: event chrdevs associated with interrupt lines
* @attached_buffers: array of buffers statically attached by the driver
* @attached_buffers_cnt: number of buffers in the array of statically attached buffers
* @buffer_ioctl_handler: ioctl() handler for this IIO device's buffer interface
* @buffer_list: list of all buffers currently attached
* @channel_attr_list: keep track of automatically created channel
* attributes
@ -28,6 +29,7 @@ struct iio_dev_opaque {
struct iio_event_interface *event_interface;
struct iio_buffer **attached_buffers;
unsigned int attached_buffers_cnt;
struct iio_ioctl_handler *buffer_ioctl_handler;
struct list_head buffer_list;
struct list_head channel_attr_list;
struct attribute_group chan_attr_group;

10
include/uapi/linux/iio/buffer.h Normal file
View File

@ -0,0 +1,10 @@
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/* industrial I/O buffer definitions needed both in and out of kernel
*/
#ifndef _UAPI_IIO_BUFFER_H_
#define _UAPI_IIO_BUFFER_H_
#define IIO_BUFFER_GET_FD_IOCTL _IOWR('i', 0x91, int)
#endif /* _UAPI_IIO_BUFFER_H_ */