This creates an example Counter program under tools/counter/*
to exemplify the Counter character device interface.

Cc: Pavel Machek <pa...@ucw.cz>
Signed-off-by: William Breathitt Gray <vilhelm.g...@gmail.com>
---
 MAINTAINERS                     |  1 +
 tools/Makefile                  | 13 ++---
 tools/counter/Build             |  1 +
 tools/counter/Makefile          | 53 ++++++++++++++++++
 tools/counter/counter_example.c | 95 +++++++++++++++++++++++++++++++++
 5 files changed, 157 insertions(+), 6 deletions(-)
 create mode 100644 tools/counter/Build
 create mode 100644 tools/counter/Makefile
 create mode 100644 tools/counter/counter_example.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 93233a07f5aa..aa61b40d02fe 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4582,6 +4582,7 @@ F:        Documentation/driver-api/generic-counter.rst
 F:     drivers/counter/
 F:     include/linux/counter.h
 F:     include/uapi/linux/counter.h
+F:     tools/counter/
 
 CPMAC ETHERNET DRIVER
 M:     Florian Fainelli <f.faine...@gmail.com>
diff --git a/tools/Makefile b/tools/Makefile
index 7e9d34ddd74c..4c26400ffc03 100644
--- 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'
        @echo '  cpupower               - a tool for all things x86 CPU power'
        @echo '  debugging              - tools for debugging'
        @echo '  firewire               - the userspace part of nosy, an 
IEEE-1394 traffic sniffer'
@@ -65,7 +66,7 @@ acpi: FORCE
 cpupower: FORCE
        $(call descend,power/$@)
 
-cgroup firewire hv guest bootconfig spi usb virtio vm bpf iio gpio objtool 
leds wmi pci firmware debugging tracing: FORCE
+cgroup counter firewire hv guest bootconfig spi usb virtio vm bpf iio gpio 
objtool leds wmi pci firmware debugging tracing: FORCE
        $(call descend,$@)
 
 bpf/%: FORCE
@@ -100,7 +101,7 @@ freefall: FORCE
 kvm_stat: FORCE
        $(call descend,kvm/$@)
 
-all: acpi cgroup cpupower gpio hv firewire liblockdep \
+all: acpi cgroup counter cpupower gpio hv firewire liblockdep \
                perf selftests bootconfig spi turbostat usb \
                virtio vm bpf x86_energy_perf_policy \
                tmon freefall iio objtool kvm_stat wmi \
@@ -112,7 +113,7 @@ acpi_install:
 cpupower_install:
        $(call descend,power/$(@:_install=),install)
 
-cgroup_install firewire_install gpio_install hv_install iio_install 
perf_install bootconfig_install spi_install usb_install virtio_install 
vm_install bpf_install objtool_install wmi_install pci_install 
debugging_install tracing_install:
+cgroup_install counter_install firewire_install gpio_install hv_install 
iio_install perf_install bootconfig_install spi_install usb_install 
virtio_install vm_install bpf_install objtool_install wmi_install pci_install 
debugging_install tracing_install:
        $(call descend,$(@:_install=),install)
 
 liblockdep_install:
@@ -133,7 +134,7 @@ freefall_install:
 kvm_stat_install:
        $(call descend,kvm/$(@:_install=),install)
 
-install: acpi_install cgroup_install cpupower_install gpio_install \
+install: acpi_install cgroup_install counter_install cpupower_install 
gpio_install \
                hv_install firewire_install iio_install liblockdep_install \
                perf_install selftests_install turbostat_install usb_install \
                virtio_install vm_install bpf_install 
x86_energy_perf_policy_install \
@@ -147,7 +148,7 @@ acpi_clean:
 cpupower_clean:
        $(call descend,power/cpupower,clean)
 
-cgroup_clean hv_clean firewire_clean bootconfig_clean spi_clean usb_clean 
virtio_clean vm_clean wmi_clean bpf_clean iio_clean gpio_clean objtool_clean 
leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
+cgroup_clean counter_clean hv_clean firewire_clean bootconfig_clean spi_clean 
usb_clean virtio_clean vm_clean wmi_clean bpf_clean iio_clean gpio_clean 
objtool_clean leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
        $(call descend,$(@:_clean=),clean)
 
 liblockdep_clean:
@@ -181,7 +182,7 @@ freefall_clean:
 build_clean:
        $(call descend,build,clean)
 
-clean: acpi_clean cgroup_clean cpupower_clean hv_clean firewire_clean \
+clean: acpi_clean cgroup_clean counter_clean cpupower_clean hv_clean 
firewire_clean \
                perf_clean selftests_clean turbostat_clean bootconfig_clean 
spi_clean usb_clean virtio_clean \
                vm_clean bpf_clean iio_clean x86_energy_perf_policy_clean 
tmon_clean \
                freefall_clean build_clean libbpf_clean libsubcmd_clean 
liblockdep_clean \
diff --git a/tools/counter/Build b/tools/counter/Build
new file mode 100644
index 000000000000..33f4a51d715e
--- /dev/null
+++ b/tools/counter/Build
@@ -0,0 +1 @@
+counter_example-y += counter_example.o
diff --git a/tools/counter/Makefile b/tools/counter/Makefile
new file mode 100644
index 000000000000..5ebc195fd9c0
--- /dev/null
+++ b/tools/counter/Makefile
@@ -0,0 +1,53 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../scripts/Makefile.include
+
+bindir ?= /usr/bin
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(CURDIR)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+# Do not use make's built-in rules
+# (this improves performance and avoids hard-to-debug behaviour);
+MAKEFLAGS += -r
+
+override CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
+
+ALL_TARGETS := counter_example
+ALL_PROGRAMS := $(patsubst %,$(OUTPUT)%,$(ALL_TARGETS))
+
+all: $(ALL_PROGRAMS)
+
+export srctree OUTPUT CC LD CFLAGS
+include $(srctree)/tools/build/Makefile.include
+
+#
+# We need the following to be outside of kernel tree
+#
+$(OUTPUT)include/linux/counter.h: ../../include/uapi/linux/counter.h
+       mkdir -p $(OUTPUT)include/linux 2>&1 || true
+       ln -sf $(CURDIR)/../../include/uapi/linux/counter.h $@
+
+prepare: $(OUTPUT)include/linux/counter.h
+
+COUNTER_EXAMPLE := $(OUTPUT)counter_example.o
+$(COUNTER_EXAMPLE): prepare FORCE
+       $(Q)$(MAKE) $(build)=counter_example
+$(OUTPUT)counter_example: $(COUNTER_EXAMPLE)
+       $(QUIET_LINK)$(CC) $(CFLAGS) $(LDFLAGS) $< -o $@
+
+clean:
+       rm -f $(ALL_PROGRAMS)
+       rm -rf $(OUTPUT)include/linux/counter.h
+       find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.d' 
-delete
+
+install: $(ALL_PROGRAMS)
+       install -d -m 755 $(DESTDIR)$(bindir);          \
+       for program in $(ALL_PROGRAMS); do              \
+               install $$program $(DESTDIR)$(bindir);  \
+       done
+
+FORCE:
+
+.PHONY: all install clean FORCE prepare
diff --git a/tools/counter/counter_example.c b/tools/counter/counter_example.c
new file mode 100644
index 000000000000..71dfec673c11
--- /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] = {
+       {
+               /* 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;
+       }
+
+       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));
+       }
+
+       return 0;
+}
-- 
2.30.1

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