linux/drivers/gpio/gpio-aggregator.c
Geert Uytterhoeven 828546e242 gpio: Add GPIO Aggregator
GPIO controllers are exported to userspace using /dev/gpiochip*
character devices.  Access control to these devices is provided by
standard UNIX file system permissions, on an all-or-nothing basis:
either a GPIO controller is accessible for a user, or it is not.
Currently no mechanism exists to control access to individual GPIOs.

Hence add a GPIO driver to aggregate existing GPIOs, and expose them as
a new gpiochip.

This supports the following use cases:
  - Aggregating GPIOs using Sysfs
    This is useful for implementing access control, and assigning a set
    of GPIOs to a specific user or virtual machine.
  - Generic GPIO Driver
    This is useful for industrial control, where it can provide
    userspace access to a simple GPIO-operated device described in DT,
    cfr. e.g. spidev for SPI-operated devices.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Link: https://lore.kernel.org/r/20200511145257.22970-5-geert+renesas@glider.be
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
2020-05-18 10:12:42 +02:00

569 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
//
// GPIO Aggregator
//
// Copyright (C) 2019-2020 Glider bv
#define DRV_NAME "gpio-aggregator"
#define pr_fmt(fmt) DRV_NAME ": " fmt
#include <linux/bitmap.h>
#include <linux/bitops.h>
#include <linux/ctype.h>
#include <linux/gpio/consumer.h>
#include <linux/gpio/driver.h>
#include <linux/gpio/machine.h>
#include <linux/idr.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/overflow.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/string.h>
/*
* GPIO Aggregator sysfs interface
*/
struct gpio_aggregator {
struct gpiod_lookup_table *lookups;
struct platform_device *pdev;
char args[];
};
static DEFINE_MUTEX(gpio_aggregator_lock); /* protects idr */
static DEFINE_IDR(gpio_aggregator_idr);
static char *get_arg(char **args)
{
char *start = *args, *end;
start = skip_spaces(start);
if (!*start)
return NULL;
if (*start == '"') {
/* Quoted arg */
end = strchr(++start, '"');
if (!end)
return ERR_PTR(-EINVAL);
} else {
/* Unquoted arg */
for (end = start; *end && !isspace(*end); end++) ;
}
if (*end)
*end++ = '\0';
*args = end;
return start;
}
static bool isrange(const char *s)
{
size_t n;
if (IS_ERR_OR_NULL(s))
return false;
while (1) {
n = strspn(s, "0123456789");
if (!n)
return false;
s += n;
switch (*s++) {
case '\0':
return true;
case '-':
case ',':
break;
default:
return false;
}
}
}
static int aggr_add_gpio(struct gpio_aggregator *aggr, const char *key,
int hwnum, unsigned int *n)
{
struct gpiod_lookup_table *lookups;
lookups = krealloc(aggr->lookups, struct_size(lookups, table, *n + 2),
GFP_KERNEL);
if (!lookups)
return -ENOMEM;
lookups->table[*n] =
(struct gpiod_lookup)GPIO_LOOKUP_IDX(key, hwnum, NULL, *n, 0);
(*n)++;
memset(&lookups->table[*n], 0, sizeof(lookups->table[*n]));
aggr->lookups = lookups;
return 0;
}
static int aggr_parse(struct gpio_aggregator *aggr)
{
unsigned int first_index, last_index, i, n = 0;
char *name, *offsets, *first, *last, *next;
char *args = aggr->args;
int error;
for (name = get_arg(&args), offsets = get_arg(&args); name;
offsets = get_arg(&args)) {
if (IS_ERR(name)) {
pr_err("Cannot get GPIO specifier: %pe\n", name);
return PTR_ERR(name);
}
if (!isrange(offsets)) {
/* Named GPIO line */
error = aggr_add_gpio(aggr, name, U16_MAX, &n);
if (error)
return error;
name = offsets;
continue;
}
/* GPIO chip + offset(s) */
for (first = offsets; *first; first = next) {
next = strchrnul(first, ',');
if (*next)
*next++ = '\0';
last = strchr(first, '-');
if (last)
*last++ = '\0';
if (kstrtouint(first, 10, &first_index)) {
pr_err("Cannot parse GPIO index %s\n", first);
return -EINVAL;
}
if (!last) {
last_index = first_index;
} else if (kstrtouint(last, 10, &last_index)) {
pr_err("Cannot parse GPIO index %s\n", last);
return -EINVAL;
}
for (i = first_index; i <= last_index; i++) {
error = aggr_add_gpio(aggr, name, i, &n);
if (error)
return error;
}
}
name = get_arg(&args);
}
if (!n) {
pr_err("No GPIOs specified\n");
return -EINVAL;
}
return 0;
}
static ssize_t new_device_store(struct device_driver *driver, const char *buf,
size_t count)
{
struct gpio_aggregator *aggr;
struct platform_device *pdev;
int res, id;
/* kernfs guarantees string termination, so count + 1 is safe */
aggr = kzalloc(sizeof(*aggr) + count + 1, GFP_KERNEL);
if (!aggr)
return -ENOMEM;
memcpy(aggr->args, buf, count + 1);
aggr->lookups = kzalloc(struct_size(aggr->lookups, table, 1),
GFP_KERNEL);
if (!aggr->lookups) {
res = -ENOMEM;
goto free_ga;
}
mutex_lock(&gpio_aggregator_lock);
id = idr_alloc(&gpio_aggregator_idr, aggr, 0, 0, GFP_KERNEL);
mutex_unlock(&gpio_aggregator_lock);
if (id < 0) {
res = id;
goto free_table;
}
aggr->lookups->dev_id = kasprintf(GFP_KERNEL, "%s.%d", DRV_NAME, id);
if (!aggr->lookups->dev_id) {
res = -ENOMEM;
goto remove_idr;
}
res = aggr_parse(aggr);
if (res)
goto free_dev_id;
gpiod_add_lookup_table(aggr->lookups);
pdev = platform_device_register_simple(DRV_NAME, id, NULL, 0);
if (IS_ERR(pdev)) {
res = PTR_ERR(pdev);
goto remove_table;
}
aggr->pdev = pdev;
return count;
remove_table:
gpiod_remove_lookup_table(aggr->lookups);
free_dev_id:
kfree(aggr->lookups->dev_id);
remove_idr:
mutex_lock(&gpio_aggregator_lock);
idr_remove(&gpio_aggregator_idr, id);
mutex_unlock(&gpio_aggregator_lock);
free_table:
kfree(aggr->lookups);
free_ga:
kfree(aggr);
return res;
}
static DRIVER_ATTR_WO(new_device);
static void gpio_aggregator_free(struct gpio_aggregator *aggr)
{
platform_device_unregister(aggr->pdev);
gpiod_remove_lookup_table(aggr->lookups);
kfree(aggr->lookups->dev_id);
kfree(aggr->lookups);
kfree(aggr);
}
static ssize_t delete_device_store(struct device_driver *driver,
const char *buf, size_t count)
{
struct gpio_aggregator *aggr;
unsigned int id;
int error;
if (!str_has_prefix(buf, DRV_NAME "."))
return -EINVAL;
error = kstrtouint(buf + strlen(DRV_NAME "."), 10, &id);
if (error)
return error;
mutex_lock(&gpio_aggregator_lock);
aggr = idr_remove(&gpio_aggregator_idr, id);
mutex_unlock(&gpio_aggregator_lock);
if (!aggr)
return -ENOENT;
gpio_aggregator_free(aggr);
return count;
}
static DRIVER_ATTR_WO(delete_device);
static struct attribute *gpio_aggregator_attrs[] = {
&driver_attr_new_device.attr,
&driver_attr_delete_device.attr,
NULL,
};
ATTRIBUTE_GROUPS(gpio_aggregator);
static int __exit gpio_aggregator_idr_remove(int id, void *p, void *data)
{
gpio_aggregator_free(p);
return 0;
}
static void __exit gpio_aggregator_remove_all(void)
{
mutex_lock(&gpio_aggregator_lock);
idr_for_each(&gpio_aggregator_idr, gpio_aggregator_idr_remove, NULL);
idr_destroy(&gpio_aggregator_idr);
mutex_unlock(&gpio_aggregator_lock);
}
/*
* GPIO Forwarder
*/
struct gpiochip_fwd {
struct gpio_chip chip;
struct gpio_desc **descs;
union {
struct mutex mlock; /* protects tmp[] if can_sleep */
spinlock_t slock; /* protects tmp[] if !can_sleep */
};
unsigned long tmp[]; /* values and descs for multiple ops */
};
static int gpio_fwd_get_direction(struct gpio_chip *chip, unsigned int offset)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
return gpiod_get_direction(fwd->descs[offset]);
}
static int gpio_fwd_direction_input(struct gpio_chip *chip, unsigned int offset)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
return gpiod_direction_input(fwd->descs[offset]);
}
static int gpio_fwd_direction_output(struct gpio_chip *chip,
unsigned int offset, int value)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
return gpiod_direction_output(fwd->descs[offset], value);
}
static int gpio_fwd_get(struct gpio_chip *chip, unsigned int offset)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
return gpiod_get_value(fwd->descs[offset]);
}
static int gpio_fwd_get_multiple(struct gpio_chip *chip, unsigned long *mask,
unsigned long *bits)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
unsigned long *values, flags = 0;
struct gpio_desc **descs;
unsigned int i, j = 0;
int error;
if (chip->can_sleep)
mutex_lock(&fwd->mlock);
else
spin_lock_irqsave(&fwd->slock, flags);
/* Both values bitmap and desc pointers are stored in tmp[] */
values = &fwd->tmp[0];
descs = (void *)&fwd->tmp[BITS_TO_LONGS(fwd->chip.ngpio)];
bitmap_clear(values, 0, fwd->chip.ngpio);
for_each_set_bit(i, mask, fwd->chip.ngpio)
descs[j++] = fwd->descs[i];
error = gpiod_get_array_value(j, descs, NULL, values);
if (!error) {
j = 0;
for_each_set_bit(i, mask, fwd->chip.ngpio)
__assign_bit(i, bits, test_bit(j++, values));
}
if (chip->can_sleep)
mutex_unlock(&fwd->mlock);
else
spin_unlock_irqrestore(&fwd->slock, flags);
return error;
}
static void gpio_fwd_set(struct gpio_chip *chip, unsigned int offset, int value)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
gpiod_set_value(fwd->descs[offset], value);
}
static void gpio_fwd_set_multiple(struct gpio_chip *chip, unsigned long *mask,
unsigned long *bits)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
unsigned long *values, flags = 0;
struct gpio_desc **descs;
unsigned int i, j = 0;
if (chip->can_sleep)
mutex_lock(&fwd->mlock);
else
spin_lock_irqsave(&fwd->slock, flags);
/* Both values bitmap and desc pointers are stored in tmp[] */
values = &fwd->tmp[0];
descs = (void *)&fwd->tmp[BITS_TO_LONGS(fwd->chip.ngpio)];
for_each_set_bit(i, mask, fwd->chip.ngpio) {
__assign_bit(j, values, test_bit(i, bits));
descs[j++] = fwd->descs[i];
}
gpiod_set_array_value(j, descs, NULL, values);
if (chip->can_sleep)
mutex_unlock(&fwd->mlock);
else
spin_unlock_irqrestore(&fwd->slock, flags);
}
static int gpio_fwd_set_config(struct gpio_chip *chip, unsigned int offset,
unsigned long config)
{
struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
return gpiod_set_config(fwd->descs[offset], config);
}
/**
* gpiochip_fwd_create() - Create a new GPIO forwarder
* @dev: Parent device pointer
* @ngpios: Number of GPIOs in the forwarder.
* @descs: Array containing the GPIO descriptors to forward to.
* This array must contain @ngpios entries, and must not be deallocated
* before the forwarder has been destroyed again.
*
* This function creates a new gpiochip, which forwards all GPIO operations to
* the passed GPIO descriptors.
*
* Return: An opaque object pointer, or an ERR_PTR()-encoded negative error
* code on failure.
*/
static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
unsigned int ngpios,
struct gpio_desc *descs[])
{
const char *label = dev_name(dev);
struct gpiochip_fwd *fwd;
struct gpio_chip *chip;
unsigned int i;
int error;
fwd = devm_kzalloc(dev, struct_size(fwd, tmp,
BITS_TO_LONGS(ngpios) + ngpios), GFP_KERNEL);
if (!fwd)
return ERR_PTR(-ENOMEM);
chip = &fwd->chip;
/*
* If any of the GPIO lines are sleeping, then the entire forwarder
* will be sleeping.
* If any of the chips support .set_config(), then the forwarder will
* support setting configs.
*/
for (i = 0; i < ngpios; i++) {
struct gpio_chip *parent = gpiod_to_chip(descs[i]);
dev_dbg(dev, "%u => gpio-%d\n", i, desc_to_gpio(descs[i]));
if (gpiod_cansleep(descs[i]))
chip->can_sleep = true;
if (parent && parent->set_config)
chip->set_config = gpio_fwd_set_config;
}
chip->label = label;
chip->parent = dev;
chip->owner = THIS_MODULE;
chip->get_direction = gpio_fwd_get_direction;
chip->direction_input = gpio_fwd_direction_input;
chip->direction_output = gpio_fwd_direction_output;
chip->get = gpio_fwd_get;
chip->get_multiple = gpio_fwd_get_multiple;
chip->set = gpio_fwd_set;
chip->set_multiple = gpio_fwd_set_multiple;
chip->base = -1;
chip->ngpio = ngpios;
fwd->descs = descs;
if (chip->can_sleep)
mutex_init(&fwd->mlock);
else
spin_lock_init(&fwd->slock);
error = devm_gpiochip_add_data(dev, chip, fwd);
if (error)
return ERR_PTR(error);
return fwd;
}
/*
* GPIO Aggregator platform device
*/
static int gpio_aggregator_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct gpio_desc **descs;
struct gpiochip_fwd *fwd;
int i, n;
n = gpiod_count(dev, NULL);
if (n < 0)
return n;
descs = devm_kmalloc_array(dev, n, sizeof(*descs), GFP_KERNEL);
if (!descs)
return -ENOMEM;
for (i = 0; i < n; i++) {
descs[i] = devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
if (IS_ERR(descs[i]))
return PTR_ERR(descs[i]);
}
fwd = gpiochip_fwd_create(dev, n, descs);
if (IS_ERR(fwd))
return PTR_ERR(fwd);
platform_set_drvdata(pdev, fwd);
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id gpio_aggregator_dt_ids[] = {
/*
* Add GPIO-operated devices controlled from userspace below,
* or use "driver_override" in sysfs
*/
{},
};
MODULE_DEVICE_TABLE(of, gpio_aggregator_dt_ids);
#endif
static struct platform_driver gpio_aggregator_driver = {
.probe = gpio_aggregator_probe,
.driver = {
.name = DRV_NAME,
.groups = gpio_aggregator_groups,
.of_match_table = of_match_ptr(gpio_aggregator_dt_ids),
},
};
static int __init gpio_aggregator_init(void)
{
return platform_driver_register(&gpio_aggregator_driver);
}
module_init(gpio_aggregator_init);
static void __exit gpio_aggregator_exit(void)
{
gpio_aggregator_remove_all();
platform_driver_unregister(&gpio_aggregator_driver);
}
module_exit(gpio_aggregator_exit);
MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
MODULE_DESCRIPTION("GPIO Aggregator");
MODULE_LICENSE("GPL v2");