From ffa247cc159228e82f93add00936e02604281344 Mon Sep 17 00:00:00 2001
From: Nikita Shubin <nikita.shubin@maquefel.me>
Date: Thu, 6 Mar 2025 14:41:15 +0300
Subject: [PATCH] add gpio-watch to monitor config events
Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
---
Makefile | 9 +++-
src/gpio-watch.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 131 insertions(+), 1 deletion(-)
create mode 100644 src/gpio-watch.c
diff --git a/Makefile b/Makefile
index 23c552e..614301e 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,8 @@ INCLUDE += -Isrc/
all: \
lsgpio \
gpio-event-mon \
- gpio-hammer
+ gpio-hammer \
+ gpio-watch
.PHONY: debug
debug: CFLAGS+= -O0 -DDEBUG -ggdb -g3 -Wno-unused-variable
@@ -56,6 +57,12 @@ gpio-hammer: gpio-hammer.o gpio-utils.o
gpio-hammer.o: src/gpio-hammer.c
$(CC) $(CFLAGS) -c src/gpio-hammer.c $(INCLUDE)
+gpio-watch: gpio-watch.o gpio-utils.o
+ $(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
+
+gpio-watch.o: src/gpio-watch.c
+ $(CC) $(CFLAGS) -c src/gpio-watch.c $(INCLUDE)
+
gpio-utils.o: src/gpio-utils.c
$(CC) $(CFLAGS) -c src/gpio-utils.c $(INCLUDE)
diff --git a/src/gpio-watch.c b/src/gpio-watch.c
new file mode 100644
index 0000000..0945040
--- /dev/null
+++ b/src/gpio-watch.c
@@ -0,0 +1,123 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * gpio-watch - monitor unrequested lines for property changes using the
+ * character device
+ *
+ * Copyright (C) 2019 BayLibre SAS
+ * Author: Bartosz Golaszewski <bgolaszewski@baylibre.com>
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/gpio.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+int main(int argc, char **argv)
+{
+ unsigned long val = GPIO_V2_GET_LINEINFO_WATCH_IOCTL;
+ struct gpio_v2_line_info_changed chg;
+ struct gpio_v2_line_info req;
+ struct sockaddr_un addr;
+ struct pollfd pfd;
+ int fd, i, j, ret;
+ char *event, *end;
+ ssize_t rd;
+
+ if (argc < 3)
+ goto err_usage;
+
+ fd = socket(AF_UNIX, SOCK_STREAM, 0);
+ memset(&addr, 0, sizeof(addr));
+
+ addr.sun_family = AF_UNIX;
+ strncpy(addr.sun_path, argv[1], sizeof(addr.sun_path) - 1);
+
+ ret = connect(fd, (const struct sockaddr *) &addr, sizeof(addr));
+ if (ret == -1) {
+ perror("unable to open gpiochip");
+ return EXIT_FAILURE;
+ }
+
+ for (i = 0, j = 2; i < argc - 2; i++, j++) {
+ memset(&req, 0, sizeof(req));
+
+ req.offset = strtoul(argv[j], &end, 0);
+ if (*end != '\0')
+ goto err_usage;
+
+ ret = write(fd, &val, sizeof(val));
+ if (ret <= 0) {
+ perror("unable to write ioctl() magick");
+ return EXIT_FAILURE;
+ }
+
+ ret = write(fd, &req, sizeof(req));
+ if (ret <= 0) {
+ perror("unable to write line watch request");
+ return EXIT_FAILURE;
+ }
+
+ ret = recv(fd, &req, sizeof(req), MSG_WAITALL);
+ if (ret != sizeof(req)) {
+ perror("unable to read line watch response");
+ return EXIT_FAILURE;
+ }
+ }
+
+ pfd.fd = fd;
+ pfd.events = POLLIN | POLLPRI;
+
+ for (;;) {
+ ret = poll(&pfd, 1, 5000);
+ if (ret < 0) {
+ perror("error polling the linechanged fd");
+ return EXIT_FAILURE;
+ } else if (ret > 0) {
+ memset(&chg, 0, sizeof(chg));
+ rd = read(pfd.fd, &chg, sizeof(chg));
+ if (rd < 0 || rd != sizeof(chg)) {
+ if (rd != sizeof(chg))
+ errno = EIO;
+
+ perror("error reading line change event");
+ return EXIT_FAILURE;
+ }
+
+ switch (chg.event_type) {
+ case GPIO_V2_LINE_CHANGED_REQUESTED:
+ event = "requested";
+ break;
+ case GPIO_V2_LINE_CHANGED_RELEASED:
+ event = "released";
+ break;
+ case GPIO_V2_LINE_CHANGED_CONFIG:
+ event = "config changed";
+ break;
+ default:
+ fprintf(stderr,
+ "invalid event type received from the kernel\n");
+ return EXIT_FAILURE;
+ }
+
+ printf("line %u: %s at %" PRIu64 "\n",
+ chg.info.offset, event, (uint64_t)chg.timestamp_ns);
+ }
+ }
+
+ return 0;
+
+err_usage:
+ printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
+ return EXIT_FAILURE;
+}
--
2.30.2