[PATCH 8/8] tools: gpio: implement gpio-watch

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>

Add a simple program that allows to test the new LINECHANGED_FD ioctl().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
---
 tools/gpio/.gitignore   |   1 +
 tools/gpio/Build        |   1 +
 tools/gpio/Makefile     |  11 +++-
 tools/gpio/gpio-watch.c | 114 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 126 insertions(+), 1 deletion(-)
 create mode 100644 tools/gpio/gpio-watch.c

diff --git a/tools/gpio/.gitignore b/tools/gpio/.gitignore
index a94c0e83b209..fffd32969d62 100644
--- a/tools/gpio/.gitignore
+++ b/tools/gpio/.gitignore
@@ -1,4 +1,5 @@
 gpio-event-mon
 gpio-hammer
 lsgpio
+gpio-watch
 include/linux/gpio.h
diff --git a/tools/gpio/Build b/tools/gpio/Build
index 4141f35837db..67c7b7f6a717 100644
--- a/tools/gpio/Build
+++ b/tools/gpio/Build
@@ -2,3 +2,4 @@ gpio-utils-y += gpio-utils.o
 lsgpio-y += lsgpio.o gpio-utils.o
 gpio-hammer-y += gpio-hammer.o gpio-utils.o
 gpio-event-mon-y += gpio-event-mon.o gpio-utils.o
+gpio-watch-y += gpio-watch.o
diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index 6080de58861f..842287e42c83 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -18,7 +18,7 @@ MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
-ALL_TARGETS := lsgpio gpio-hammer gpio-event-mon
+ALL_TARGETS := lsgpio gpio-hammer gpio-event-mon gpio-watch
 ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))
 
 all: $(ALL_PROGRAMS)
@@ -66,6 +66,15 @@ $(GPIO_EVENT_MON_IN): prepare FORCE $(OUTPUT)gpio-utils-in.o
 $(OUTPUT)gpio-event-mon: $(GPIO_EVENT_MON_IN)
 	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
 
+#
+# gpio-watch
+#
+GPIO_WATCH_IN := $(OUTPUT)gpio-watch-in.o
+$(GPIO_WATCH_IN): prepare FORCE
+	$(Q)$(MAKE) $(build)=gpio-watch
+$(OUTPUT)gpio-watch: $(GPIO_WATCH_IN)
+	$(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
+
 clean:
 	rm -f $(ALL_PROGRAMS)
 	rm -f $(OUTPUT)include/linux/gpio.h
diff --git a/tools/gpio/gpio-watch.c b/tools/gpio/gpio-watch.c
new file mode 100644
index 000000000000..7107ab24be52
--- /dev/null
+++ b/tools/gpio/gpio-watch.c
@@ -0,0 +1,114 @@
+// 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@xxxxxxxxxxxx>
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.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 <unistd.h>
+
+static bool isnumber(const char *str)
+{
+	size_t sz = strlen(str);
+	int i;
+
+	for (i = 0; i < sz; i++) {
+		if (!isdigit(str[i]))
+			return false;
+	}
+
+	return true;
+}
+
+int main(int argc, char **argv)
+{
+	struct gpioline_changed_fd_request lc_req;
+	struct gpioline_changed chg;
+	struct pollfd pfd;
+	int fd, i, j, ret;
+	char *event;
+	ssize_t rd;
+
+	if (argc < 3)
+		goto err_usage;
+
+	fd = open(argv[1], O_RDWR | O_CLOEXEC);
+	if (fd < 0) {
+		perror("unable to open gpiochip");
+		return EXIT_FAILURE;
+	}
+
+	memset(&lc_req, 0, sizeof(lc_req));
+
+	for (i = 0, j = 2; i < argc - 2; i++, j++) {
+		if (!isnumber(argv[j]))
+			goto err_usage;
+
+		lc_req.lineoffsets[i] = atoi(argv[j]);
+	}
+
+	lc_req.num_lines = argc - 2;
+
+	ret = ioctl(fd, GPIO_GET_LINECHANGED_FD_IOCTL, &lc_req);
+	if (ret < 0) {
+		perror("unable to retrieve the linechanged fd");
+		return EXIT_FAILURE;
+	}
+
+	pfd.fd = lc_req.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 GPIOLINE_CHANGED_REQUESTED:
+				event = "requested";
+				break;
+			case GPIOLINE_CHANGED_RELEASED:
+				event = "released";
+				break;
+			case GPIOLINE_CHANGED_CONFIG:
+				event = "config changed";
+				break;
+			default:
+				fprintf(stderr,
+					"invalid event type received from the kernel\n");
+				return EXIT_FAILURE;
+			}
+
+			printf("line %u: %s\n", chg.line_offset, event);
+		}
+	}
+
+	return 0;
+
+err_usage:
+	printf("%s: <gpiochip> <line0> <line1> ...\n", argv[0]);
+	return EXIT_FAILURE;
+}
-- 
2.23.0