| /* The industrial I/O simple minimally locked ring buffer. |
| * |
| * Copyright (c) 2008 Jonathan Cameron |
| * |
| * 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/slab.h> |
| #include <linux/kernel.h> |
| #include <linux/module.h> |
| #include <linux/device.h> |
| #include <linux/workqueue.h> |
| #include <linux/sched.h> |
| #include <linux/poll.h> |
| #include "ring_sw.h" |
| #include "trigger.h" |
| |
| /** |
| * struct iio_sw_ring_buffer - software ring buffer |
| * @buf: generic ring buffer elements |
| * @data: the ring buffer memory |
| * @read_p: read pointer (oldest available) |
| * @write_p: write pointer |
| * @half_p: half buffer length behind write_p (event generation) |
| * @update_needed: flag to indicated change in size requested |
| * |
| * Note that the first element of all ring buffers must be a |
| * struct iio_buffer. |
| **/ |
| struct iio_sw_ring_buffer { |
| struct iio_buffer buf; |
| unsigned char *data; |
| unsigned char *read_p; |
| unsigned char *write_p; |
| /* used to act as a point at which to signal an event */ |
| unsigned char *half_p; |
| int update_needed; |
| }; |
| |
| #define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf) |
| |
| static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring, |
| int bytes_per_datum, int length) |
| { |
| if ((length == 0) || (bytes_per_datum == 0)) |
| return -EINVAL; |
| __iio_update_buffer(&ring->buf, bytes_per_datum, length); |
| ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC); |
| ring->read_p = NULL; |
| ring->write_p = NULL; |
| ring->half_p = NULL; |
| return ring->data ? 0 : -ENOMEM; |
| } |
| |
| static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring) |
| { |
| kfree(ring->data); |
| } |
| |
| /* Ring buffer related functionality */ |
| /* Store to ring is typically called in the bh of a data ready interrupt handler |
| * in the device driver */ |
| /* Lock always held if their is a chance this may be called */ |
| /* Only one of these per ring may run concurrently - enforced by drivers */ |
| static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring, |
| unsigned char *data, s64 timestamp) |
| { |
| int ret = 0; |
| unsigned char *temp_ptr, *change_test_ptr; |
| |
| /* initial store */ |
| if (unlikely(ring->write_p == NULL)) { |
| ring->write_p = ring->data; |
| /* Doesn't actually matter if this is out of the set |
| * as long as the read pointer is valid before this |
| * passes it - guaranteed as set later in this function. |
| */ |
| ring->half_p = ring->data - ring->buf.length*ring->buf.bytes_per_datum/2; |
| } |
| /* Copy data to where ever the current write pointer says */ |
| memcpy(ring->write_p, data, ring->buf.bytes_per_datum); |
| barrier(); |
| /* Update the pointer used to get most recent value. |
| * Always valid as either points to latest or second latest value. |
| * Before this runs it is null and read attempts fail with -EAGAIN. |
| */ |
| barrier(); |
| /* temp_ptr used to ensure we never have an invalid pointer |
| * it may be slightly lagging, but never invalid |
| */ |
| temp_ptr = ring->write_p + ring->buf.bytes_per_datum; |
| /* End of ring, back to the beginning */ |
| if (temp_ptr == ring->data + ring->buf.length*ring->buf.bytes_per_datum) |
| temp_ptr = ring->data; |
| /* Update the write pointer |
| * always valid as long as this is the only function able to write. |
| * Care needed with smp systems to ensure more than one ring fill |
| * is never scheduled. |
| */ |
| ring->write_p = temp_ptr; |
| |
| if (ring->read_p == NULL) |
| ring->read_p = ring->data; |
| /* Buffer full - move the read pointer and create / escalate |
| * ring event */ |
| /* Tricky case - if the read pointer moves before we adjust it. |
| * Handle by not pushing if it has moved - may result in occasional |
| * unnecessary buffer full events when it wasn't quite true. |
| */ |
| else if (ring->write_p == ring->read_p) { |
| change_test_ptr = ring->read_p; |
| temp_ptr = change_test_ptr + ring->buf.bytes_per_datum; |
| if (temp_ptr |
| == ring->data + ring->buf.length*ring->buf.bytes_per_datum) { |
| temp_ptr = ring->data; |
| } |
| /* We are moving pointer on one because the ring is full. Any |
| * change to the read pointer will be this or greater. |
| */ |
| if (change_test_ptr == ring->read_p) |
| ring->read_p = temp_ptr; |
| } |
| /* investigate if our event barrier has been passed */ |
| /* There are definite 'issues' with this and chances of |
| * simultaneous read */ |
| /* Also need to use loop count to ensure this only happens once */ |
| ring->half_p += ring->buf.bytes_per_datum; |
| if (ring->half_p == ring->data + ring->buf.length*ring->buf.bytes_per_datum) |
| ring->half_p = ring->data; |
| if (ring->half_p == ring->read_p) { |
| ring->buf.stufftoread = true; |
| wake_up_interruptible(&ring->buf.pollq); |
| } |
| return ret; |
| } |
| |
| static int iio_read_first_n_sw_rb(struct iio_buffer *r, |
| size_t n, char __user *buf) |
| { |
| struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r); |
| |
| u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p; |
| u8 *data; |
| int ret, max_copied, bytes_to_rip, dead_offset; |
| size_t data_available, buffer_size; |
| |
| /* A userspace program has probably made an error if it tries to |
| * read something that is not a whole number of bpds. |
| * Return an error. |
| */ |
| if (n % ring->buf.bytes_per_datum) { |
| ret = -EINVAL; |
| printk(KERN_INFO "Ring buffer read request not whole number of" |
| "samples: Request bytes %zd, Current bytes per datum %d\n", |
| n, ring->buf.bytes_per_datum); |
| goto error_ret; |
| } |
| |
| buffer_size = ring->buf.bytes_per_datum*ring->buf.length; |
| |
| /* Limit size to whole of ring buffer */ |
| bytes_to_rip = min_t(size_t, buffer_size, n); |
| |
| data = kmalloc(bytes_to_rip, GFP_KERNEL); |
| if (data == NULL) { |
| ret = -ENOMEM; |
| goto error_ret; |
| } |
| |
| /* build local copy */ |
| initial_read_p = ring->read_p; |
| if (unlikely(initial_read_p == NULL)) { /* No data here as yet */ |
| ret = 0; |
| goto error_free_data_cpy; |
| } |
| |
| initial_write_p = ring->write_p; |
| |
| /* Need a consistent pair */ |
| while ((initial_read_p != ring->read_p) |
| || (initial_write_p != ring->write_p)) { |
| initial_read_p = ring->read_p; |
| initial_write_p = ring->write_p; |
| } |
| if (initial_write_p == initial_read_p) { |
| /* No new data available.*/ |
| ret = 0; |
| goto error_free_data_cpy; |
| } |
| |
| if (initial_write_p >= initial_read_p) |
| data_available = initial_write_p - initial_read_p; |
| else |
| data_available = buffer_size - (initial_read_p - initial_write_p); |
| |
| if (data_available < bytes_to_rip) |
| bytes_to_rip = data_available; |
| |
| if (initial_read_p + bytes_to_rip >= ring->data + buffer_size) { |
| max_copied = ring->data + buffer_size - initial_read_p; |
| memcpy(data, initial_read_p, max_copied); |
| memcpy(data + max_copied, ring->data, bytes_to_rip - max_copied); |
| end_read_p = ring->data + bytes_to_rip - max_copied; |
| } else { |
| memcpy(data, initial_read_p, bytes_to_rip); |
| end_read_p = initial_read_p + bytes_to_rip; |
| } |
| |
| /* Now to verify which section was cleanly copied - i.e. how far |
| * read pointer has been pushed */ |
| current_read_p = ring->read_p; |
| |
| if (initial_read_p <= current_read_p) |
| dead_offset = current_read_p - initial_read_p; |
| else |
| dead_offset = buffer_size - (initial_read_p - current_read_p); |
| |
| /* possible issue if the initial write has been lapped or indeed |
| * the point we were reading to has been passed */ |
| /* No valid data read. |
| * In this case the read pointer is already correct having been |
| * pushed further than we would look. */ |
| if (bytes_to_rip - dead_offset < 0) { |
| ret = 0; |
| goto error_free_data_cpy; |
| } |
| |
| /* setup the next read position */ |
| /* Beware, this may fail due to concurrency fun and games. |
| * Possible that sufficient fill commands have run to push the read |
| * pointer past where we would be after the rip. If this occurs, leave |
| * it be. |
| */ |
| /* Tricky - deal with loops */ |
| |
| while (ring->read_p != end_read_p) |
| ring->read_p = end_read_p; |
| |
| ret = bytes_to_rip - dead_offset; |
| |
| if (copy_to_user(buf, data + dead_offset, ret)) { |
| ret = -EFAULT; |
| goto error_free_data_cpy; |
| } |
| |
| if (bytes_to_rip >= ring->buf.length*ring->buf.bytes_per_datum/2) |
| ring->buf.stufftoread = 0; |
| |
| error_free_data_cpy: |
| kfree(data); |
| error_ret: |
| |
| return ret; |
| } |
| |
| static int iio_store_to_sw_rb(struct iio_buffer *r, |
| u8 *data, |
| s64 timestamp) |
| { |
| struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r); |
| return iio_store_to_sw_ring(ring, data, timestamp); |
| } |
| |
| static int iio_request_update_sw_rb(struct iio_buffer *r) |
| { |
| int ret = 0; |
| struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r); |
| |
| r->stufftoread = false; |
| if (!ring->update_needed) |
| goto error_ret; |
| __iio_free_sw_ring_buffer(ring); |
| ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum, |
| ring->buf.length); |
| error_ret: |
| return ret; |
| } |
| |
| static int iio_get_bytes_per_datum_sw_rb(struct iio_buffer *r) |
| { |
| struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r); |
| return ring->buf.bytes_per_datum; |
| } |
| |
| static int iio_mark_update_needed_sw_rb(struct iio_buffer *r) |
| { |
| struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r); |
| ring->update_needed = true; |
| return 0; |
| } |
| |
| static int iio_set_bytes_per_datum_sw_rb(struct iio_buffer *r, size_t bpd) |
| { |
| if (r->bytes_per_datum != bpd) { |
| r->bytes_per_datum = bpd; |
| iio_mark_update_needed_sw_rb(r); |
| } |
| return 0; |
| } |
| |
| static int iio_get_length_sw_rb(struct iio_buffer *r) |
| { |
| return r->length; |
| } |
| |
| static int iio_set_length_sw_rb(struct iio_buffer *r, int length) |
| { |
| if (r->length != length) { |
| r->length = length; |
| iio_mark_update_needed_sw_rb(r); |
| } |
| return 0; |
| } |
| |
| static IIO_BUFFER_ENABLE_ATTR; |
| static IIO_BUFFER_LENGTH_ATTR; |
| |
| /* Standard set of ring buffer attributes */ |
| static struct attribute *iio_ring_attributes[] = { |
| &dev_attr_length.attr, |
| &dev_attr_enable.attr, |
| NULL, |
| }; |
| |
| static struct attribute_group iio_ring_attribute_group = { |
| .attrs = iio_ring_attributes, |
| .name = "buffer", |
| }; |
| |
| struct iio_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev) |
| { |
| struct iio_buffer *buf; |
| struct iio_sw_ring_buffer *ring; |
| |
| ring = kzalloc(sizeof *ring, GFP_KERNEL); |
| if (!ring) |
| return NULL; |
| ring->update_needed = true; |
| buf = &ring->buf; |
| iio_buffer_init(buf); |
| buf->attrs = &iio_ring_attribute_group; |
| |
| return buf; |
| } |
| EXPORT_SYMBOL(iio_sw_rb_allocate); |
| |
| void iio_sw_rb_free(struct iio_buffer *r) |
| { |
| kfree(iio_to_sw_ring(r)); |
| } |
| EXPORT_SYMBOL(iio_sw_rb_free); |
| |
| const struct iio_buffer_access_funcs ring_sw_access_funcs = { |
| .store_to = &iio_store_to_sw_rb, |
| .read_first_n = &iio_read_first_n_sw_rb, |
| .request_update = &iio_request_update_sw_rb, |
| .get_bytes_per_datum = &iio_get_bytes_per_datum_sw_rb, |
| .set_bytes_per_datum = &iio_set_bytes_per_datum_sw_rb, |
| .get_length = &iio_get_length_sw_rb, |
| .set_length = &iio_set_length_sw_rb, |
| }; |
| EXPORT_SYMBOL(ring_sw_access_funcs); |
| |
| MODULE_DESCRIPTION("Industrialio I/O software ring buffer"); |
| MODULE_LICENSE("GPL"); |