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/*
* SPDX-FileCopyrightText: 2021-2024 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include "esp_vfs_eventfd.h"
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/lock.h>
#include <sys/select.h>
#include <sys/types.h>
#include "esp_err.h"
#include "esp_log.h"
#include "esp_vfs.h"
#include "freertos/FreeRTOS.h"
#include "freertos/portmacro.h"
#include "spinlock.h"
#define FD_INVALID -1
#define FD_PENDING_SELECT -2
/*
* About the event_select_args_t linked list
*
* Each event_select_args_t structure records a pending select from a select call
* on a file descriptor.
*
* For each select() call, we form a linked list in end_select_args containing
* all the pending selects in this select call.
*
* For each file descriptor, we form a double linked list in event_context_t::select_args.
* This list contains all the pending selects on this file descriptor from
* different select() calls.
*
*/
typedef struct event_select_args_t {
int fd;
fd_set *read_fds;
fd_set *error_fds;
esp_vfs_select_sem_t signal_sem;
// linked list node in event_context_t::select_args
struct event_select_args_t *prev_in_fd;
struct event_select_args_t *next_in_fd;
// linked list node in end_select_arg
struct event_select_args_t *next_in_args;
} event_select_args_t;
typedef struct {
int fd;
bool support_isr;
volatile bool is_set;
volatile uint64_t value;
// a double-linked list for all pending select args with this fd
event_select_args_t *select_args;
_lock_t lock;
// only for event fds that support ISR.
portMUX_TYPE data_spin_lock;
} event_context_t;
esp_vfs_id_t s_eventfd_vfs_id = -1;
static size_t s_event_size;
static event_context_t *s_events;
static void trigger_select_for_event(event_context_t *event)
{
event_select_args_t *select_args = event->select_args;
while (select_args != NULL) {
esp_vfs_select_triggered(select_args->signal_sem);
select_args = select_args->next_in_fd;
}
}
static void trigger_select_for_event_isr(event_context_t *event, BaseType_t *task_woken)
{
event_select_args_t *select_args = event->select_args;
while (select_args != NULL) {
BaseType_t local_woken;
esp_vfs_select_triggered_isr(select_args->signal_sem, &local_woken);
*task_woken = (local_woken || *task_woken);
select_args = select_args->next_in_fd;
}
}
#ifdef CONFIG_VFS_SUPPORT_SELECT
static esp_err_t event_start_select(int nfds,
fd_set *readfds,
fd_set *writefds,
fd_set *exceptfds,
esp_vfs_select_sem_t signal_sem,
void **end_select_args)
{
esp_err_t error = ESP_OK;
bool should_trigger = false;
nfds = nfds < s_event_size ? nfds : (int)s_event_size;
event_select_args_t *select_args_list = NULL;
// FIXME: end_select_args should be a list to all select args
for (int i = 0; i < nfds; i++) {
_lock_acquire_recursive(&s_events[i].lock);
if (s_events[i].fd == i && (FD_ISSET(i, readfds) || FD_ISSET(i, writefds) || FD_ISSET(i, exceptfds))) {
event_select_args_t *event_select_args =
(event_select_args_t *)malloc(sizeof(event_select_args_t));
if (!event_select_args) {
_lock_release_recursive(&s_events[i].lock);
return ESP_ERR_NO_MEM;
}
if (s_events[i].support_isr) {
portENTER_CRITICAL(&s_events[i].data_spin_lock);
}
event_select_args->fd = i;
event_select_args->signal_sem = signal_sem;
if (FD_ISSET(i, exceptfds)) {
FD_CLR(i, exceptfds);
event_select_args->error_fds = exceptfds;
} else {
event_select_args->error_fds = NULL;
}
FD_CLR(i, exceptfds);
// event fds are always writable
if (FD_ISSET(i, writefds)) {
should_trigger = true;
}
if (FD_ISSET(i, readfds)) {
event_select_args->read_fds = readfds;
if (s_events[i].is_set) {
should_trigger = true;
} else {
FD_CLR(i, readfds);
}
} else {
event_select_args->read_fds = NULL;
}
event_select_args->prev_in_fd = NULL;
event_select_args->next_in_fd = s_events[i].select_args;
if (s_events[i].select_args) {
s_events[i].select_args->prev_in_fd = event_select_args;
}
event_select_args->next_in_args = select_args_list;
select_args_list = event_select_args;
s_events[i].select_args = event_select_args;
if (s_events[i].support_isr) {
portEXIT_CRITICAL(&s_events[i].data_spin_lock);
}
}
_lock_release_recursive(&s_events[i].lock);
}
*end_select_args = select_args_list;
if (should_trigger) {
esp_vfs_select_triggered(signal_sem);
}
return error;
}
static esp_err_t event_end_select(void *end_select_args)
{
event_select_args_t *select_args = (event_select_args_t *)end_select_args;
while (select_args != NULL) {
event_context_t *event = &s_events[select_args->fd];
_lock_acquire_recursive(&event->lock);
if (event->support_isr) {
portENTER_CRITICAL(&event->data_spin_lock);
}
if (event->fd != select_args->fd) { // already closed
if (select_args->error_fds) {
FD_SET(select_args->fd, select_args->error_fds);
}
} else {
if (select_args->read_fds && event->is_set) {
FD_SET(select_args->fd, select_args->read_fds);
}
}
event_select_args_t *prev_in_fd = select_args->prev_in_fd;
event_select_args_t *next_in_fd = select_args->next_in_fd;
event_select_args_t *next_in_args = select_args->next_in_args;
if (prev_in_fd != NULL) {
prev_in_fd->next_in_fd = next_in_fd;
} else {
event->select_args = next_in_fd;
}
if (next_in_fd != NULL) {
next_in_fd->prev_in_fd = prev_in_fd;
}
if (prev_in_fd == NULL && next_in_fd == NULL) { // The last pending select
if (event->fd == FD_PENDING_SELECT) {
event->fd = FD_INVALID;
}
}
if (event->support_isr) {
portEXIT_CRITICAL(&event->data_spin_lock);
}
_lock_release_recursive(&event->lock);
free(select_args);
select_args = next_in_args;
}
return ESP_OK;
}
#endif // CONFIG_VFS_SUPPORT_SELECT
static ssize_t signal_event_fd_from_isr(int fd, const void *data, size_t size)
{
BaseType_t task_woken = pdFALSE;
const uint64_t *val = (const uint64_t *)data;
ssize_t ret = size;
portENTER_CRITICAL_ISR(&s_events[fd].data_spin_lock);
if (s_events[fd].fd == fd) {
s_events[fd].is_set = true;
s_events[fd].value += *val;
trigger_select_for_event_isr(&s_events[fd], &task_woken);
} else {
errno = EBADF;
ret = -1;
}
portEXIT_CRITICAL_ISR(&s_events[fd].data_spin_lock);
if (task_woken) {
portYIELD_FROM_ISR();
}
return ret;
}
static ssize_t event_write(int fd, const void *data, size_t size)
{
ssize_t ret = -1;
if (fd >= s_event_size || data == NULL || size != sizeof(uint64_t)) {
errno = EINVAL;
return ret;
}
if (size != sizeof(uint64_t)) {
errno = EINVAL;
return ret;
}
if (!xPortCanYield()) {
ret = signal_event_fd_from_isr(fd, data, size);
} else {
const uint64_t *val = (const uint64_t *)data;
_lock_acquire_recursive(&s_events[fd].lock);
if (s_events[fd].support_isr) {
portENTER_CRITICAL(&s_events[fd].data_spin_lock);
}
if (s_events[fd].fd == fd) {
s_events[fd].is_set = true;
s_events[fd].value += *val;
ret = size;
trigger_select_for_event(&s_events[fd]);
} else {
errno = EBADF;
ret = -1;
}
if (s_events[fd].support_isr) {
portEXIT_CRITICAL(&s_events[fd].data_spin_lock);
}
_lock_release_recursive(&s_events[fd].lock);
}
return ret;
}
static ssize_t event_read(int fd, void *data, size_t size)
{
ssize_t ret = -1;
if (fd >= s_event_size || data == NULL || size != sizeof(uint64_t)) {
errno = EINVAL;
return ret;
}
uint64_t *val = (uint64_t *)data;
_lock_acquire_recursive(&s_events[fd].lock);
if (s_events[fd].support_isr) {
portENTER_CRITICAL(&s_events[fd].data_spin_lock);
}
if (s_events[fd].fd == fd) {
*val = s_events[fd].value;
s_events[fd].is_set = false;
ret = size;
s_events[fd].value = 0;
} else {
errno = EBADF;
ret = -1;
}
if (s_events[fd].support_isr) {
portEXIT_CRITICAL(&s_events[fd].data_spin_lock);
}
_lock_release_recursive(&s_events[fd].lock);
return ret;
}
static int event_close(int fd)
{
int ret = -1;
if (fd >= s_event_size) {
errno = EINVAL;
return ret;
}
_lock_acquire_recursive(&s_events[fd].lock);
if (s_events[fd].fd == fd) {
if (s_events[fd].support_isr) {
portENTER_CRITICAL(&s_events[fd].data_spin_lock);
}
if (s_events[fd].select_args == NULL) {
s_events[fd].fd = FD_INVALID;
} else {
s_events[fd].fd = FD_PENDING_SELECT;
trigger_select_for_event(&s_events[fd]);
}
s_events[fd].value = 0;
if (s_events[fd].support_isr) {
portEXIT_CRITICAL(&s_events[fd].data_spin_lock);
}
ret = 0;
} else {
errno = EBADF;
}
_lock_release_recursive(&s_events[fd].lock);
return ret;
}
esp_err_t esp_vfs_eventfd_register(const esp_vfs_eventfd_config_t *config)
{
if (config == NULL || config->max_fds >= MAX_FDS) {
return ESP_ERR_INVALID_ARG;
}
if (s_eventfd_vfs_id != -1) {
return ESP_ERR_INVALID_STATE;
}
s_event_size = config->max_fds;
s_events = (event_context_t *)calloc(s_event_size, sizeof(event_context_t));
for (size_t i = 0; i < s_event_size; i++) {
_lock_init_recursive(&s_events[i].lock);
s_events[i].fd = FD_INVALID;
}
esp_vfs_t vfs = {
.flags = ESP_VFS_FLAG_DEFAULT,
.write = &event_write,
.close = &event_close,
.read = &event_read,
#ifdef CONFIG_VFS_SUPPORT_SELECT
.start_select = &event_start_select,
.end_select = &event_end_select,
#endif
};
return esp_vfs_register_with_id(&vfs, NULL, &s_eventfd_vfs_id);
}
esp_err_t esp_vfs_eventfd_unregister(void)
{
if (s_eventfd_vfs_id == -1) {
return ESP_ERR_INVALID_STATE;
}
esp_err_t error = esp_vfs_unregister_with_id(s_eventfd_vfs_id);
if (error == ESP_OK) {
s_eventfd_vfs_id = -1;
}
for (size_t i = 0; i < s_event_size; i++) {
_lock_close_recursive(&s_events[i].lock);
}
free(s_events);
return error;
}
int eventfd(unsigned int initval, int flags)
{
int fd = FD_INVALID;
int global_fd = FD_INVALID;
esp_err_t error = ESP_OK;
if ((flags & (~EFD_SUPPORT_ISR)) != 0) {
errno = EINVAL;
return FD_INVALID;
}
if (s_eventfd_vfs_id == -1) {
errno = EACCES;
return FD_INVALID;
}
for (size_t i = 0; i < s_event_size; i++) {
_lock_acquire_recursive(&s_events[i].lock);
if (s_events[i].fd == FD_INVALID) {
error = esp_vfs_register_fd_with_local_fd(s_eventfd_vfs_id, i, /*permanent=*/false, &global_fd);
if (error != ESP_OK) {
_lock_release_recursive(&s_events[i].lock);
break;
}
bool support_isr = flags & EFD_SUPPORT_ISR;
fd = i;
s_events[i].fd = i;
s_events[i].support_isr = support_isr;
portMUX_INITIALIZE(&s_events[i].data_spin_lock);
if (support_isr) {
portENTER_CRITICAL(&s_events[i].data_spin_lock);
}
s_events[i].is_set = false;
s_events[i].value = initval;
s_events[i].select_args = NULL;
if (support_isr) {
portEXIT_CRITICAL(&s_events[i].data_spin_lock);
}
_lock_release_recursive(&s_events[i].lock);
break;
}
_lock_release_recursive(&s_events[i].lock);
}
switch (error) {
case ESP_OK:
fd = global_fd;
break;
case ESP_ERR_NO_MEM:
errno = ENOMEM;
break;
case ESP_ERR_INVALID_ARG:
errno = EINVAL;
break;
default:
errno = EIO;
break;
}
return fd;
}
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