f73f7f4da5
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>
53 lines
2.0 KiB
C
53 lines
2.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _INDUSTRIAL_IO_OPAQUE_H_
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#define _INDUSTRIAL_IO_OPAQUE_H_
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/**
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* struct iio_dev_opaque - industrial I/O device opaque information
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* @indio_dev: public industrial I/O device information
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* @event_interface: event chrdevs associated with interrupt lines
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* @attached_buffers: array of buffers statically attached by the driver
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* @attached_buffers_cnt: number of buffers in the array of statically attached buffers
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* @buffer_ioctl_handler: ioctl() handler for this IIO device's buffer interface
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* @buffer_list: list of all buffers currently attached
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* @channel_attr_list: keep track of automatically created channel
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* attributes
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* @chan_attr_group: group for all attrs in base directory
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* @ioctl_handlers: ioctl handlers registered with the core handler
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* @groups: attribute groups
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* @groupcounter: index of next attribute group
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* @legacy_scan_el_group: attribute group for legacy scan elements attribute group
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* @legacy_buffer_group: attribute group for legacy buffer attributes group
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* @debugfs_dentry: device specific debugfs dentry
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* @cached_reg_addr: cached register address for debugfs reads
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* @read_buf: read buffer to be used for the initial reg read
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* @read_buf_len: data length in @read_buf
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*/
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struct iio_dev_opaque {
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struct iio_dev indio_dev;
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struct iio_event_interface *event_interface;
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struct iio_buffer **attached_buffers;
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unsigned int attached_buffers_cnt;
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struct iio_ioctl_handler *buffer_ioctl_handler;
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struct list_head buffer_list;
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struct list_head channel_attr_list;
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struct attribute_group chan_attr_group;
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struct list_head ioctl_handlers;
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const struct attribute_group **groups;
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int groupcounter;
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struct attribute_group legacy_scan_el_group;
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struct attribute_group legacy_buffer_group;
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#if defined(CONFIG_DEBUG_FS)
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struct dentry *debugfs_dentry;
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unsigned cached_reg_addr;
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char read_buf[20];
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unsigned int read_buf_len;
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#endif
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};
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#define to_iio_dev_opaque(indio_dev) \
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container_of(indio_dev, struct iio_dev_opaque, indio_dev)
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#endif
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