On 7/11/21 6:28 AM, William Breathitt Gray wrote:
On Sat, Jul 10, 2021 at 11:53:35AM -0500, David Lechner wrote:
On 7/5/21 3:19 AM, William Breathitt Gray wrote:
+ {
+ /* 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errno is no longer valid after calling perror().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).
Ack.
+ }
+
+ 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?
Watch 0 and Watch 1 are both triggered by the same event: a
COUNTER_EVENT_INDEX event on device event channel 0. If we had set
channel to 1 for Watch 1, then we would have two independent events, but
in this case both Watches have their respective channel set to 0.
The thing that jumped out to me is that they have different parents.
But I guess I forgot that the event itself always has a scope of
device and that the component just says what value to record and
is otherwise independent of the event.
