linux/drivers/mux/core.c

547 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Multiplexer subsystem
*
* Copyright (C) 2017 Axentia Technologies AB
*
* Author: Peter Rosin <peda@axentia.se>
*/
#define pr_fmt(fmt) "mux-core: " fmt
#include <linux/device.h>
#include <linux/err.h>
#include <linux/export.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mux/consumer.h>
#include <linux/mux/driver.h>
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/slab.h>
/*
* The idle-as-is "state" is not an actual state that may be selected, it
* only implies that the state should not be changed. So, use that state
* as indication that the cached state of the multiplexer is unknown.
*/
#define MUX_CACHE_UNKNOWN MUX_IDLE_AS_IS
static struct class mux_class = {
.name = "mux",
.owner = THIS_MODULE,
};
static DEFINE_IDA(mux_ida);
static int __init mux_init(void)
{
ida_init(&mux_ida);
return class_register(&mux_class);
}
static void __exit mux_exit(void)
{
class_unregister(&mux_class);
ida_destroy(&mux_ida);
}
static void mux_chip_release(struct device *dev)
{
struct mux_chip *mux_chip = to_mux_chip(dev);
ida_simple_remove(&mux_ida, mux_chip->id);
kfree(mux_chip);
}
static const struct device_type mux_type = {
.name = "mux-chip",
.release = mux_chip_release,
};
/**
* mux_chip_alloc() - Allocate a mux-chip.
* @dev: The parent device implementing the mux interface.
* @controllers: The number of mux controllers to allocate for this chip.
* @sizeof_priv: Size of extra memory area for private use by the caller.
*
* After allocating the mux-chip with the desired number of mux controllers
* but before registering the chip, the mux driver is required to configure
* the number of valid mux states in the mux_chip->mux[N].states members and
* the desired idle state in the returned mux_chip->mux[N].idle_state members.
* The default idle state is MUX_IDLE_AS_IS. The mux driver also needs to
* provide a pointer to the operations struct in the mux_chip->ops member
* before registering the mux-chip with mux_chip_register.
*
* Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
*/
struct mux_chip *mux_chip_alloc(struct device *dev,
unsigned int controllers, size_t sizeof_priv)
{
struct mux_chip *mux_chip;
int i;
if (WARN_ON(!dev || !controllers))
return ERR_PTR(-EINVAL);
mux_chip = kzalloc(sizeof(*mux_chip) +
controllers * sizeof(*mux_chip->mux) +
sizeof_priv, GFP_KERNEL);
if (!mux_chip)
return ERR_PTR(-ENOMEM);
mux_chip->mux = (struct mux_control *)(mux_chip + 1);
mux_chip->dev.class = &mux_class;
mux_chip->dev.type = &mux_type;
mux_chip->dev.parent = dev;
mux_chip->dev.of_node = dev->of_node;
dev_set_drvdata(&mux_chip->dev, mux_chip);
mux_chip->id = ida_simple_get(&mux_ida, 0, 0, GFP_KERNEL);
if (mux_chip->id < 0) {
int err = mux_chip->id;
pr_err("muxchipX failed to get a device id\n");
kfree(mux_chip);
return ERR_PTR(err);
}
dev_set_name(&mux_chip->dev, "muxchip%d", mux_chip->id);
mux_chip->controllers = controllers;
for (i = 0; i < controllers; ++i) {
struct mux_control *mux = &mux_chip->mux[i];
mux->chip = mux_chip;
sema_init(&mux->lock, 1);
mux->cached_state = MUX_CACHE_UNKNOWN;
mux->idle_state = MUX_IDLE_AS_IS;
}
device_initialize(&mux_chip->dev);
return mux_chip;
}
EXPORT_SYMBOL_GPL(mux_chip_alloc);
static int mux_control_set(struct mux_control *mux, int state)
{
int ret = mux->chip->ops->set(mux, state);
mux->cached_state = ret < 0 ? MUX_CACHE_UNKNOWN : state;
return ret;
}
/**
* mux_chip_register() - Register a mux-chip, thus readying the controllers
* for use.
* @mux_chip: The mux-chip to register.
*
* Do not retry registration of the same mux-chip on failure. You should
* instead put it away with mux_chip_free() and allocate a new one, if you
* for some reason would like to retry registration.
*
* Return: Zero on success or a negative errno on error.
*/
int mux_chip_register(struct mux_chip *mux_chip)
{
int i;
int ret;
for (i = 0; i < mux_chip->controllers; ++i) {
struct mux_control *mux = &mux_chip->mux[i];
if (mux->idle_state == mux->cached_state)
continue;
ret = mux_control_set(mux, mux->idle_state);
if (ret < 0) {
dev_err(&mux_chip->dev, "unable to set idle state\n");
return ret;
}
}
ret = device_add(&mux_chip->dev);
if (ret < 0)
dev_err(&mux_chip->dev,
"device_add failed in %s: %d\n", __func__, ret);
return ret;
}
EXPORT_SYMBOL_GPL(mux_chip_register);
/**
* mux_chip_unregister() - Take the mux-chip off-line.
* @mux_chip: The mux-chip to unregister.
*
* mux_chip_unregister() reverses the effects of mux_chip_register().
* But not completely, you should not try to call mux_chip_register()
* on a mux-chip that has been registered before.
*/
void mux_chip_unregister(struct mux_chip *mux_chip)
{
device_del(&mux_chip->dev);
}
EXPORT_SYMBOL_GPL(mux_chip_unregister);
/**
* mux_chip_free() - Free the mux-chip for good.
* @mux_chip: The mux-chip to free.
*
* mux_chip_free() reverses the effects of mux_chip_alloc().
*/
void mux_chip_free(struct mux_chip *mux_chip)
{
if (!mux_chip)
return;
put_device(&mux_chip->dev);
}
EXPORT_SYMBOL_GPL(mux_chip_free);
static void devm_mux_chip_release(struct device *dev, void *res)
{
struct mux_chip *mux_chip = *(struct mux_chip **)res;
mux_chip_free(mux_chip);
}
/**
* devm_mux_chip_alloc() - Resource-managed version of mux_chip_alloc().
* @dev: The parent device implementing the mux interface.
* @controllers: The number of mux controllers to allocate for this chip.
* @sizeof_priv: Size of extra memory area for private use by the caller.
*
* See mux_chip_alloc() for more details.
*
* Return: A pointer to the new mux-chip, or an ERR_PTR with a negative errno.
*/
struct mux_chip *devm_mux_chip_alloc(struct device *dev,
unsigned int controllers,
size_t sizeof_priv)
{
struct mux_chip **ptr, *mux_chip;
ptr = devres_alloc(devm_mux_chip_release, sizeof(*ptr), GFP_KERNEL);
if (!ptr)
return ERR_PTR(-ENOMEM);
mux_chip = mux_chip_alloc(dev, controllers, sizeof_priv);
if (IS_ERR(mux_chip)) {
devres_free(ptr);
return mux_chip;
}
*ptr = mux_chip;
devres_add(dev, ptr);
return mux_chip;
}
EXPORT_SYMBOL_GPL(devm_mux_chip_alloc);
static void devm_mux_chip_reg_release(struct device *dev, void *res)
{
struct mux_chip *mux_chip = *(struct mux_chip **)res;
mux_chip_unregister(mux_chip);
}
/**
* devm_mux_chip_register() - Resource-managed version mux_chip_register().
* @dev: The parent device implementing the mux interface.
* @mux_chip: The mux-chip to register.
*
* See mux_chip_register() for more details.
*
* Return: Zero on success or a negative errno on error.
*/
int devm_mux_chip_register(struct device *dev,
struct mux_chip *mux_chip)
{
struct mux_chip **ptr;
int res;
ptr = devres_alloc(devm_mux_chip_reg_release, sizeof(*ptr), GFP_KERNEL);
if (!ptr)
return -ENOMEM;
res = mux_chip_register(mux_chip);
if (res) {
devres_free(ptr);
return res;
}
*ptr = mux_chip;
devres_add(dev, ptr);
return res;
}
EXPORT_SYMBOL_GPL(devm_mux_chip_register);
/**
* mux_control_states() - Query the number of multiplexer states.
* @mux: The mux-control to query.
*
* Return: The number of multiplexer states.
*/
unsigned int mux_control_states(struct mux_control *mux)
{
return mux->states;
}
EXPORT_SYMBOL_GPL(mux_control_states);
/*
* The mux->lock must be down when calling this function.
*/
static int __mux_control_select(struct mux_control *mux, int state)
{
int ret;
if (WARN_ON(state < 0 || state >= mux->states))
return -EINVAL;
if (mux->cached_state == state)
return 0;
ret = mux_control_set(mux, state);
if (ret >= 0)
return 0;
/* The mux update failed, try to revert if appropriate... */
if (mux->idle_state != MUX_IDLE_AS_IS)
mux_control_set(mux, mux->idle_state);
return ret;
}
/**
* mux_control_select() - Select the given multiplexer state.
* @mux: The mux-control to request a change of state from.
* @state: The new requested state.
*
* On successfully selecting the mux-control state, it will be locked until
* there is a call to mux_control_deselect(). If the mux-control is already
* selected when mux_control_select() is called, the caller will be blocked
* until mux_control_deselect() is called (by someone else).
*
* Therefore, make sure to call mux_control_deselect() when the operation is
* complete and the mux-control is free for others to use, but do not call
* mux_control_deselect() if mux_control_select() fails.
*
* Return: 0 when the mux-control state has the requested state or a negative
* errno on error.
*/
int mux_control_select(struct mux_control *mux, unsigned int state)
{
int ret;
ret = down_killable(&mux->lock);
if (ret < 0)
return ret;
ret = __mux_control_select(mux, state);
if (ret < 0)
up(&mux->lock);
return ret;
}
EXPORT_SYMBOL_GPL(mux_control_select);
/**
* mux_control_try_select() - Try to select the given multiplexer state.
* @mux: The mux-control to request a change of state from.
* @state: The new requested state.
*
* On successfully selecting the mux-control state, it will be locked until
* mux_control_deselect() called.
*
* Therefore, make sure to call mux_control_deselect() when the operation is
* complete and the mux-control is free for others to use, but do not call
* mux_control_deselect() if mux_control_try_select() fails.
*
* Return: 0 when the mux-control state has the requested state or a negative
* errno on error. Specifically -EBUSY if the mux-control is contended.
*/
int mux_control_try_select(struct mux_control *mux, unsigned int state)
{
int ret;
if (down_trylock(&mux->lock))
return -EBUSY;
ret = __mux_control_select(mux, state);
if (ret < 0)
up(&mux->lock);
return ret;
}
EXPORT_SYMBOL_GPL(mux_control_try_select);
/**
* mux_control_deselect() - Deselect the previously selected multiplexer state.
* @mux: The mux-control to deselect.
*
* It is required that a single call is made to mux_control_deselect() for
* each and every successful call made to either of mux_control_select() or
* mux_control_try_select().
*
* Return: 0 on success and a negative errno on error. An error can only
* occur if the mux has an idle state. Note that even if an error occurs, the
* mux-control is unlocked and is thus free for the next access.
*/
int mux_control_deselect(struct mux_control *mux)
{
int ret = 0;
if (mux->idle_state != MUX_IDLE_AS_IS &&
mux->idle_state != mux->cached_state)
ret = mux_control_set(mux, mux->idle_state);
up(&mux->lock);
return ret;
}
EXPORT_SYMBOL_GPL(mux_control_deselect);
static int of_dev_node_match(struct device *dev, const void *data)
{
return dev->of_node == data;
}
/* Note this function returns a reference to the mux_chip dev. */
static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
{
struct device *dev;
dev = class_find_device(&mux_class, NULL, np, of_dev_node_match);
return dev ? to_mux_chip(dev) : NULL;
}
/**
* mux_control_get() - Get the mux-control for a device.
* @dev: The device that needs a mux-control.
* @mux_name: The name identifying the mux-control.
*
* Return: A pointer to the mux-control, or an ERR_PTR with a negative errno.
*/
struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
{
struct device_node *np = dev->of_node;
struct of_phandle_args args;
struct mux_chip *mux_chip;
unsigned int controller;
int index = 0;
int ret;
if (mux_name) {
index = of_property_match_string(np, "mux-control-names",
mux_name);
if (index < 0) {
dev_err(dev, "mux controller '%s' not found\n",
mux_name);
return ERR_PTR(index);
}
}
ret = of_parse_phandle_with_args(np,
"mux-controls", "#mux-control-cells",
index, &args);
if (ret) {
dev_err(dev, "%pOF: failed to get mux-control %s(%i)\n",
np, mux_name ?: "", index);
return ERR_PTR(ret);
}
mux_chip = of_find_mux_chip_by_node(args.np);
of_node_put(args.np);
if (!mux_chip)
return ERR_PTR(-EPROBE_DEFER);
if (args.args_count > 1 ||
(!args.args_count && (mux_chip->controllers > 1))) {
dev_err(dev, "%pOF: wrong #mux-control-cells for %pOF\n",
np, args.np);
put_device(&mux_chip->dev);
return ERR_PTR(-EINVAL);
}
controller = 0;
if (args.args_count)
controller = args.args[0];
if (controller >= mux_chip->controllers) {
dev_err(dev, "%pOF: bad mux controller %u specified in %pOF\n",
np, controller, args.np);
put_device(&mux_chip->dev);
return ERR_PTR(-EINVAL);
}
return &mux_chip->mux[controller];
}
EXPORT_SYMBOL_GPL(mux_control_get);
/**
* mux_control_put() - Put away the mux-control for good.
* @mux: The mux-control to put away.
*
* mux_control_put() reverses the effects of mux_control_get().
*/
void mux_control_put(struct mux_control *mux)
{
put_device(&mux->chip->dev);
}
EXPORT_SYMBOL_GPL(mux_control_put);
static void devm_mux_control_release(struct device *dev, void *res)
{
struct mux_control *mux = *(struct mux_control **)res;
mux_control_put(mux);
}
/**
* devm_mux_control_get() - Get the mux-control for a device, with resource
* management.
* @dev: The device that needs a mux-control.
* @mux_name: The name identifying the mux-control.
*
* Return: Pointer to the mux-control, or an ERR_PTR with a negative errno.
*/
struct mux_control *devm_mux_control_get(struct device *dev,
const char *mux_name)
{
struct mux_control **ptr, *mux;
ptr = devres_alloc(devm_mux_control_release, sizeof(*ptr), GFP_KERNEL);
if (!ptr)
return ERR_PTR(-ENOMEM);
mux = mux_control_get(dev, mux_name);
if (IS_ERR(mux)) {
devres_free(ptr);
return mux;
}
*ptr = mux;
devres_add(dev, ptr);
return mux;
}
EXPORT_SYMBOL_GPL(devm_mux_control_get);
/*
* Using subsys_initcall instead of module_init here to try to ensure - for
* the non-modular case - that the subsystem is initialized when mux consumers
* and mux controllers start to use it.
* For the modular case, the ordering is ensured with module dependencies.
*/
subsys_initcall(mux_init);
module_exit(mux_exit);
MODULE_DESCRIPTION("Multiplexer subsystem");
MODULE_AUTHOR("Peter Rosin <peda@axentia.se>");
MODULE_LICENSE("GPL v2");