From f73f7f4da581875f9b1f2fb8ebd1ab15ed634488 Mon Sep 17 00:00:00 2001 From: Alexandru Ardelean Date: Mon, 15 Feb 2021 12:40:39 +0200 Subject: 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 #include #include #include #include #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 Link: https://lore.kernel.org/r/20210215104043.91251-21-alexandru.ardelean@analog.com Signed-off-by: Jonathan Cameron --- include/linux/iio/iio-opaque.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/iio/iio-opaque.h') diff --git a/include/linux/iio/iio-opaque.h b/include/linux/iio/iio-opaque.h index b6ebc04af3e7..32addd5e790e 100644 --- a/include/linux/iio/iio-opaque.h +++ b/include/linux/iio/iio-opaque.h @@ -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; -- cgit v1.2.3