On 7/5/21 3:19 AM, William Breathitt Gray wrote:
This creates an example Counter program under tools/counter/*
to exemplify the Counter character device interface.
Cc: Pavel Machek <pavel@xxxxxx>
Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
---
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -12,6 +12,7 @@ help:
@echo ' acpi - ACPI tools'
@echo ' bpf - misc BPF tools'
@echo ' cgroup - cgroup tools'
+ @echo ' counter - Counter tools'
nit: other descriptions start with lower case letter, so to be
consistent, this should too
--- /dev/null
+++ b/tools/counter/counter_example.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Counter - example userspace application
+ *
+ * The userspace application opens /dev/counter0, configures the
+ * COUNTER_EVENT_INDEX event channel 0 to gather Count 0 count and Count
+ * 1 count, and prints out the data as it becomes available on the
+ * character device node.
+ *
+ * Copyright (C) 2021 William Breathitt Gray
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/counter.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+struct counter_watch watches[2] = {
nit: this can be static
+ {
+ /* Component data: Count 0 count */
+ .component.type = COUNTER_COMPONENT_COUNT,
+ .component.scope = COUNTER_SCOPE_COUNT,
+ .component.parent = 0,
+ /* Event type: Index */
+ .event = COUNTER_EVENT_INDEX,
+ /* Device event channel 0 */
+ .channel = 0,
+ },
+ {
+ /* Component data: Count 1 count */
+ .component.type = COUNTER_COMPONENT_COUNT,
+ .component.scope = COUNTER_SCOPE_COUNT,
+ .component.parent = 1,
+ /* Event type: Index */
+ .event = COUNTER_EVENT_INDEX,
+ /* Device event channel 0 */
+ .channel = 0,
+ },
+};
+
+int main(void)
+{
+ int fd;
+ int ret;
+ struct counter_event event_data[2];
+
+ fd = open("/dev/counter0", O_RDWR);
+ if (fd == -1) {
+ perror("Unable to open /dev/counter0");
+ return -errno;
errno is no longer valid after calling perror(). Since this
is example code, we can just return 1 instead (exit codes
positive number between 0 and 255 so -1 would be 255).
+ }
+
+ ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches);
+ if (ret == -1) {
+ perror("Error adding watches[0]");
+ return -errno;
+ }
+ ret = ioctl(fd, COUNTER_ADD_WATCH_IOCTL, watches + 1);
+ if (ret == -1) {
+ perror("Error adding watches[1]");
+ return -errno;
+ }
+ ret = ioctl(fd, COUNTER_ENABLE_EVENTS_IOCTL);
+ if (ret == -1) {
+ perror("Error enabling events");
+ return -errno;
+ }
+
+ for (;;) {
+ ret = read(fd, event_data, sizeof(event_data));
+ if (ret == -1) {
+ perror("Failed to read event data");
+ return -errno;
+ }
+
+ if (ret != sizeof(event_data)) {
+ fprintf(stderr, "Failed to read event data\n");
+ return -EIO;
+ }
+
+ printf("Timestamp 0: %llu\tCount 0: %llu\n"
+ "Error Message 0: %s\n"
+ "Timestamp 1: %llu\tCount 1: %llu\n"
+ "Error Message 1: %s\n",
+ (unsigned long long)event_data[0].timestamp,
+ (unsigned long long)event_data[0].value,
+ strerror(event_data[0].status),
+ (unsigned long long)event_data[1].timestamp,
+ (unsigned long long)event_data[1].value,
+ strerror(event_data[1].status));
+ }
Aren't the Count 0 and Count 1 events independent? Why should we expect to
always get both events at the same time in the same order?
+
+ return 0;
+}
