OVMS3-idf/components/vfs/vfs_uart.c
Ivan Grokhotkov 13ef3938a6 vfs_uart: fix write operation blocked by a read
vfs_uart used same locks for read and write operations on a single UART.
If read operation was blocking (i.e. carried out via UART driver), the
lock was held by reading task until it received a line. During this time,
other tasks trying to write to the same UART would get blocked.

This change introduces separate read/write locks, and adds a test.

Another vfs_uart test if fixed (it was disabled since the
CONFIG_NEWLIB_STDOUT_ADDCR option was removed).
2017-08-29 08:27:36 +08:00

306 lines
8.6 KiB
C

// Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <string.h>
#include <stdbool.h>
#include <stdarg.h>
#include <sys/errno.h>
#include <sys/lock.h>
#include <sys/fcntl.h>
#include "esp_vfs.h"
#include "esp_vfs_dev.h"
#include "esp_attr.h"
#include "soc/uart_struct.h"
#include "driver/uart.h"
#include "sdkconfig.h"
// TODO: make the number of UARTs chip dependent
#define UART_NUM 3
// Token signifying that no character is available
#define NONE -1
// UART write bytes function type
typedef void (*tx_func_t)(int, int);
// UART read bytes function type
typedef int (*rx_func_t)(int);
// Basic functions for sending and receiving bytes over UART
static void uart_tx_char(int fd, int c);
static int uart_rx_char(int fd);
// Functions for sending and receiving bytes which use UART driver
static void uart_tx_char_via_driver(int fd, int c);
static int uart_rx_char_via_driver(int fd);
// Pointers to UART peripherals
static uart_dev_t* s_uarts[UART_NUM] = {&UART0, &UART1, &UART2};
// per-UART locks, lazily initialized
static _lock_t s_uart_read_locks[UART_NUM];
static _lock_t s_uart_write_locks[UART_NUM];
// One-character buffer used for newline conversion code, per UART
static int s_peek_char[UART_NUM] = { NONE, NONE, NONE };
// Per-UART non-blocking flag. Note: default implementation does not honor this
// flag, all reads are non-blocking. This option becomes effective if UART
// driver is used.
static bool s_non_blocking[UART_NUM];
// Newline conversion mode when transmitting
static esp_line_endings_t s_tx_mode =
#if CONFIG_NEWLIB_STDOUT_LINE_ENDING_CRLF
ESP_LINE_ENDINGS_CRLF;
#elif CONFIG_NEWLIB_STDOUT_LINE_ENDING_CR
ESP_LINE_ENDINGS_CR;
#else
ESP_LINE_ENDINGS_LF;
#endif
// Newline conversion mode when receiving
static esp_line_endings_t s_rx_mode =
#if CONFIG_NEWLIB_STDIN_LINE_ENDING_CRLF
ESP_LINE_ENDINGS_CRLF;
#elif CONFIG_NEWLIB_STDIN_LINE_ENDING_CR
ESP_LINE_ENDINGS_CR;
#else
ESP_LINE_ENDINGS_LF;
#endif
// Functions used to write bytes to UART. Default to "basic" functions.
static tx_func_t s_uart_tx_func[UART_NUM] = {
&uart_tx_char, &uart_tx_char, &uart_tx_char
};
// Functions used to read bytes from UART. Default to "basic" functions.
static rx_func_t s_uart_rx_func[UART_NUM] = {
&uart_rx_char, &uart_rx_char, &uart_rx_char
};
static int uart_open(const char * path, int flags, int mode)
{
// this is fairly primitive, we should check if file is opened read only,
// and error out if write is requested
if (strcmp(path, "/0") == 0) {
return 0;
} else if (strcmp(path, "/1") == 0) {
return 1;
} else if (strcmp(path, "/2") == 0) {
return 2;
}
errno = ENOENT;
return -1;
}
static void uart_tx_char(int fd, int c)
{
uart_dev_t* uart = s_uarts[fd];
while (uart->status.txfifo_cnt >= 127) {
;
}
uart->fifo.rw_byte = c;
}
static void uart_tx_char_via_driver(int fd, int c)
{
char ch = (char) c;
uart_write_bytes(fd, &ch, 1);
}
static int uart_rx_char(int fd)
{
uart_dev_t* uart = s_uarts[fd];
if (uart->status.rxfifo_cnt == 0) {
return NONE;
}
return uart->fifo.rw_byte;
}
static int uart_rx_char_via_driver(int fd)
{
uint8_t c;
int timeout = s_non_blocking[fd] ? 0 : portMAX_DELAY;
int n = uart_read_bytes(fd, &c, 1, timeout);
if (n <= 0) {
return NONE;
}
return c;
}
static ssize_t uart_write(int fd, const void * data, size_t size)
{
assert(fd >=0 && fd < 3);
const char *data_c = (const char *)data;
/* Even though newlib does stream locking on each individual stream, we need
* a dedicated UART lock if two streams (stdout and stderr) point to the
* same UART.
*/
_lock_acquire_recursive(&s_uart_write_locks[fd]);
for (size_t i = 0; i < size; i++) {
int c = data_c[i];
if (c == '\n' && s_tx_mode != ESP_LINE_ENDINGS_LF) {
s_uart_tx_func[fd](fd, '\r');
if (s_tx_mode == ESP_LINE_ENDINGS_CR) {
continue;
}
}
s_uart_tx_func[fd](fd, c);
}
_lock_release_recursive(&s_uart_write_locks[fd]);
return size;
}
/* Helper function which returns a previous character or reads a new one from
* UART. Previous character can be returned ("pushed back") using
* uart_return_char function.
*/
static int uart_read_char(int fd)
{
/* return character from peek buffer, if it is there */
if (s_peek_char[fd] != NONE) {
int c = s_peek_char[fd];
s_peek_char[fd] = NONE;
return c;
}
return s_uart_rx_func[fd](fd);
}
/* Push back a character; it will be returned by next call to uart_read_char */
static void uart_return_char(int fd, int c)
{
assert(s_peek_char[fd] == NONE);
s_peek_char[fd] = c;
}
static ssize_t uart_read(int fd, void* data, size_t size)
{
assert(fd >=0 && fd < 3);
char *data_c = (char *) data;
size_t received = 0;
_lock_acquire_recursive(&s_uart_read_locks[fd]);
while (received < size) {
int c = uart_read_char(fd);
if (c == '\r') {
if (s_rx_mode == ESP_LINE_ENDINGS_CR) {
c = '\n';
} else if (s_rx_mode == ESP_LINE_ENDINGS_CRLF) {
/* look ahead */
int c2 = uart_read_char(fd);
if (c2 == NONE) {
/* could not look ahead, put the current character back */
uart_return_char(fd, c);
break;
}
if (c2 == '\n') {
/* this was \r\n sequence. discard \r, return \n */
c = '\n';
} else {
/* \r followed by something else. put the second char back,
* it will be processed on next iteration. return \r now.
*/
uart_return_char(fd, c2);
}
}
} else if (c == NONE) {
break;
}
data_c[received] = (char) c;
++received;
if (c == '\n') {
break;
}
}
_lock_release_recursive(&s_uart_read_locks[fd]);
if (received > 0) {
return received;
}
errno = EWOULDBLOCK;
return -1;
}
static int uart_fstat(int fd, struct stat * st)
{
assert(fd >=0 && fd < 3);
st->st_mode = S_IFCHR;
return 0;
}
static int uart_close(int fd)
{
assert(fd >=0 && fd < 3);
return 0;
}
static int uart_fcntl(int fd, int cmd, va_list args)
{
assert(fd >=0 && fd < 3);
int result = 0;
if (cmd == F_GETFL) {
if (s_non_blocking[fd]) {
result |= O_NONBLOCK;
}
} else if (cmd == F_SETFL) {
int arg = va_arg(args, int);
s_non_blocking[fd] = (arg & O_NONBLOCK) != 0;
} else {
// unsupported operation
result = -1;
errno = ENOSYS;
}
return result;
}
void esp_vfs_dev_uart_register()
{
esp_vfs_t vfs = {
.fd_offset = 0,
.flags = ESP_VFS_FLAG_DEFAULT,
.write = &uart_write,
.open = &uart_open,
.fstat = &uart_fstat,
.close = &uart_close,
.read = &uart_read,
.fcntl = &uart_fcntl
};
ESP_ERROR_CHECK(esp_vfs_register("/dev/uart", &vfs, NULL));
}
void esp_vfs_dev_uart_set_rx_line_endings(esp_line_endings_t mode)
{
s_rx_mode = mode;
}
void esp_vfs_dev_uart_set_tx_line_endings(esp_line_endings_t mode)
{
s_tx_mode = mode;
}
void esp_vfs_dev_uart_use_nonblocking(int fd)
{
_lock_acquire_recursive(&s_uart_read_locks[fd]);
_lock_acquire_recursive(&s_uart_write_locks[fd]);
s_uart_tx_func[fd] = uart_tx_char;
s_uart_rx_func[fd] = uart_rx_char;
_lock_release_recursive(&s_uart_write_locks[fd]);
_lock_release_recursive(&s_uart_read_locks[fd]);
}
void esp_vfs_dev_uart_use_driver(int fd)
{
_lock_acquire_recursive(&s_uart_read_locks[fd]);
_lock_acquire_recursive(&s_uart_write_locks[fd]);
s_uart_tx_func[fd] = uart_tx_char_via_driver;
s_uart_rx_func[fd] = uart_rx_char_via_driver;
_lock_release_recursive(&s_uart_write_locks[fd]);
_lock_release_recursive(&s_uart_read_locks[fd]);
}