path: root/drivers/iio/industrialio-backend.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Framework to handle complex IIO aggregate devices.
 *
 * The typical architecture is to have one device as the frontend device which
 * can be "linked" against one or multiple backend devices. All the IIO and
 * userspace interface is expected to be registers/managed by the frontend
 * device which will callback into the backends when needed (to get/set some
 * configuration that it does not directly control).
 *
 *                                           -------------------------------------------------------
 * ------------------                        | ------------         ------------      -------  FPGA|
 * |     ADC        |------------------------| | ADC CORE |---------| DMA CORE |------| RAM |      |
 * | (Frontend/IIO) | Serial Data (eg: LVDS) | |(backend) |---------|          |------|     |      |
 * |                |------------------------| ------------         ------------      -------      |
 * ------------------                        -------------------------------------------------------
 *
 * The framework interface is pretty simple:
 *   - Backends should register themselves with devm_iio_backend_register()
 *   - Frontend devices should get backends with devm_iio_backend_get()
 *
 * Also to note that the primary target for this framework are converters like
 * ADC/DACs so iio_backend_ops will have some operations typical of converter
 * devices. On top of that, this is "generic" for all IIO which means any kind
 * of device can make use of the framework. That said, If the iio_backend_ops
 * struct begins to grow out of control, we can always refactor things so that
 * the industrialio-backend.c is only left with the really generic stuff. Then,
 * we can build on top of it depending on the needs.
 *
 * Copyright (C) 2023-2024 Analog Devices Inc.
 */
#define dev_fmt(fmt) "iio-backend: " fmt

#include <linux/cleanup.h>
#include <linux/debugfs.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/property.h>
#include <linux/slab.h>
#include <linux/stringify.h>
#include <linux/types.h>

#include <linux/iio/backend.h>
#include <linux/iio/iio.h>

struct iio_backend {
	struct list_head entry;
	const struct iio_backend_ops *ops;
	struct device *frontend_dev;
	struct device *dev;
	struct module *owner;
	void *priv;
	const char *name;
	unsigned int cached_reg_addr;
	/*
	 * This index is relative to the frontend. Meaning that for
	 * frontends with multiple backends, this will be the index of this
	 * backend. Used for the debugfs directory name.
	 */
	u8 idx;
};

/*
 * Helper struct for requesting buffers. This ensures that we have all data
 * that we need to free the buffer in a device managed action.
 */
struct iio_backend_buffer_pair {
	struct iio_backend *back;
	struct iio_buffer *buffer;
};

static LIST_HEAD(iio_back_list);
static DEFINE_MUTEX(iio_back_lock);

/*
 * Helper macros to call backend ops. Makes sure the option is supported.
 */
#define iio_backend_check_op(back, op) ({ \
	struct iio_backend *____back = back;				\
	int ____ret = 0;						\
									\
	if (!____back->ops->op)						\
		____ret = -EOPNOTSUPP;					\
									\
	____ret;							\
})

#define iio_backend_op_call(back, op, args...) ({		\
	struct iio_backend *__back = back;			\
	int __ret;						\
								\
	__ret = iio_backend_check_op(__back, op);		\
	if (!__ret)						\
		__ret = __back->ops->op(__back, ##args);	\
								\
	__ret;							\
})

#define iio_backend_ptr_op_call(back, op, args...) ({		\
	struct iio_backend *__back = back;			\
	void *ptr_err;						\
	int __ret;						\
								\
	__ret = iio_backend_check_op(__back, op);		\
	if (__ret)						\
		ptr_err = ERR_PTR(__ret);			\
	else							\
		ptr_err = __back->ops->op(__back, ##args);	\
								\
	ptr_err;						\
})

#define iio_backend_void_op_call(back, op, args...) {		\
	struct iio_backend *__back = back;			\
	int __ret;						\
								\
	__ret = iio_backend_check_op(__back, op);		\
	if (!__ret)						\
		__back->ops->op(__back, ##args);		\
	else							\
		dev_dbg(__back->dev, "Op(%s) not implemented\n",\
			__stringify(op));			\
}

static ssize_t iio_backend_debugfs_read_reg(struct file *file,
					    char __user *userbuf,
					    size_t count, loff_t *ppos)
{
	struct iio_backend *back = file->private_data;
	char read_buf[20];
	unsigned int val;
	int ret, len;

	ret = iio_backend_op_call(back, debugfs_reg_access,
				  back->cached_reg_addr, 0, &val);
	if (ret)
		return ret;

	len = scnprintf(read_buf, sizeof(read_buf), "0x%X\n", val);

	return simple_read_from_buffer(userbuf, count, ppos, read_buf, len);
}

static ssize_t iio_backend_debugfs_write_reg(struct file *file,
					     const char __user *userbuf,
					     size_t count, loff_t *ppos)
{
	struct iio_backend *back = file->private_data;
	unsigned int val;
	char buf[80];
	ssize_t rc;
	int ret;

	if (count >= sizeof(buf))
		return -ENOSPC;

	rc = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count);
	if (rc < 0)
		return rc;

	buf[rc] = '\0&