Re: [PATCH v12 12/17] tools/counter: Create Counter tools
From: David Lechner <david@lechnology.com>
Date: 2021-07-10 16:53:45
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linux-iio, lkml
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 <redacted> Signed-off-by: William Breathitt Gray <redacted> ---
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--- 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
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--- /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+ return -errno;errno is no longer valid after calling perror().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; +}
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