tools/gpio: add the gpio-hammer tool

The gpio-hammer is used from userspace as an example of how
to retrieve a GPIO handle for one or several GPIO lines and
hammer the outputs from low to high and back again. It will
pulse the selected lines once per second for a specified
number of times or indefinitely if no loop count is
supplied.

Example output:
$ gpio-hammer -n gpiochip0 -o5 -o6 -o7
Hammer lines [5, 6, 7] on gpiochip0, initial states: [1, 1, 1]
[-] [5: 0, 6: 0, 7: 0]

Tested-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 192 insertions, 2 deletions

diff --git a/tools/gpio/Makefile b/tools/gpio/Makefile
index c155d6bc47a7..aea23949054e 100644
--- a/tools/gpio/Makefile
+++ b/tools/gpio/Makefile
@@ -1,12 +1,13 @@
 CC = $(CROSS_COMPILE)gcc
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE
 
-all: lsgpio
+all: lsgpio gpio-hammer
 
 lsgpio: lsgpio.o gpio-utils.o
+gpio-hammer: gpio-hammer.o gpio-utils.o
 
 %.o: %.c gpio-utils.h
 
 .PHONY: clean
 clean:
-        rm -f *.o lsgpio
+        rm -f *.o lsgpio gpio-hammer
diff --git a/tools/gpio/gpio-hammer.c b/tools/gpio/gpio-hammer.c
new file mode 100644
index 000000000000..37b3f141053d
--- /dev/null
+++ b/tools/gpio/gpio-hammer.c
@@ -0,0 +1,189 @@
+/*
+ * gpio-hammer - example swiss army knife to shake GPIO lines on a system
+ *
+ * Copyright (C) 2016 Linus Walleij
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * Usage:
+ *      gpio-hammer -n <device-name> -o <offset1> -o <offset2>
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <poll.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <sys/ioctl.h>
+#include <linux/gpio.h>
+
+int hammer_device(const char *device_name, unsigned int *lines, int nlines,
+                  unsigned int loops)
+{
+        struct gpiohandle_request req;
+        struct gpiohandle_data data;
+        char *chrdev_name;
+        char swirr[] = "-\\|/";
+        int fd;
+        int ret;
+        int i, j;
+        unsigned int iteration = 0;
+
+        ret = asprintf(&chrdev_name, "/dev/%s", device_name);
+        if (ret < 0)
+                return -ENOMEM;
+
+        fd = open(chrdev_name, 0);
+        if (fd == -1) {
+                ret = -errno;
+                fprintf(stderr, "Failed to open %s\n", chrdev_name);
+                goto exit_close_error;
+        }
+
+        /* Request lines as output */
+        for (i = 0; i < nlines; i++)
+                req.lineoffsets[i] = lines[i];
+        req.flags = GPIOHANDLE_REQUEST_OUTPUT; /* Request as output */
+        strcpy(req.consumer_label, "gpio-hammer");
+        req.lines = nlines;
+        ret = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &req);
+        if (ret == -1) {
+                ret = -errno;
+                fprintf(stderr, "Failed to issue GET LINEHANDLE "
+                        "IOCTL (%d)\n",
+                        ret);
+                goto exit_close_error;
+        }
+
+        /* Read initial states */
+        ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
+        if (ret == -1) {
+                ret = -errno;
+                fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
+                        "VALUES IOCTL (%d)\n",
+                        ret);
+                goto exit_close_error;
+        }
+        fprintf(stdout, "Hammer lines [");
+        for (i = 0; i < nlines; i++) {
+                fprintf(stdout, "%d", lines[i]);
+                if (i != (nlines - 1))
+                        fprintf(stdout, ", ");
+        }
+        fprintf(stdout, "] on %s, initial states: [", device_name);
+        for (i = 0; i < nlines; i++) {
+                fprintf(stdout, "%d", data.values[i]);
+                if (i != (nlines - 1))
+                        fprintf(stdout, ", ");
+        }
+        fprintf(stdout, "]\n");
+
+        /* Hammertime! */
+        j = 0;
+        while (1) {
+                /* Invert all lines so we blink */
+                for (i = 0; i < nlines; i++)
+                        data.values[i] = !data.values[i];
+
+                ret = ioctl(req.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data);
+                if (ret == -1) {
+                        ret = -errno;
+                        fprintf(stderr, "Failed to issue GPIOHANDLE SET LINE "
+                                "VALUES IOCTL (%d)\n",
+                                ret);
+                        goto exit_close_error;
+                }
+                /* Re-read values to get status */
+                ret = ioctl(req.fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, &data);
+                if (ret == -1) {
+                        ret = -errno;
+                        fprintf(stderr, "Failed to issue GPIOHANDLE GET LINE "
+                                "VALUES IOCTL (%d)\n",
+                                ret);
+                        goto exit_close_error;
+                }
+
+                fprintf(stdout, "[%c] ", swirr[j]);
+                j++;
+                if (j == sizeof(swirr)-1)
+                        j = 0;
+
+                fprintf(stdout, "[");
+                for (i = 0; i < nlines; i++) {
+                        fprintf(stdout, "%d: %d", lines[i], data.values[i]);
+                        if (i != (nlines - 1))
+                                fprintf(stdout, ", ");
+                }
+                fprintf(stdout, "]\r");
+                fflush(stdout);
+                sleep(1);
+                iteration++;
+                if (loops && iteration == loops)
+                        break;
+        }
+        fprintf(stdout, "\n");
+        ret = 0;
+
+exit_close_error:
+        if (close(fd) == -1)
+                perror("Failed to close GPIO character device file");
+        free(chrdev_name);
+        return ret;
+}
+
+void print_usage(void)
+{
+        fprintf(stderr, "Usage: gpio-hammer [options]...\n"
+                "Hammer GPIO lines, 0->1->0->1...\n"
+                "  -n <name>  Hammer GPIOs on a named device (must be stated)\n"
+                "  -o <n>     Offset[s] to hammer, at least one, several can be stated\n"
+                " [-c <n>]    Do <n> loops (optional, infinite loop if not stated)\n"
+                "  -?         This helptext\n"
+                "\n"
+                "Example:\n"
+                "gpio-hammer -n gpiochip0 -o 4\n"
+        );
+}
+
+int main(int argc, char **argv)
+{
+        const char *device_name = NULL;
+        unsigned int lines[GPIOHANDLES_MAX];
+        unsigned int loops = 0;
+        int nlines;
+        int c;
+        int i;
+
+        i = 0;
+        while ((c = getopt(argc, argv, "c:n:o:?")) != -1) {
+                switch (c) {
+                case 'c':
+                        loops = strtoul(optarg, NULL, 10);
+                        break;
+                case 'n':
+                        device_name = optarg;
+                        break;
+                case 'o':
+                        lines[i] = strtoul(optarg, NULL, 10);
+                        i++;
+                        break;
+                case '?':
+                        print_usage();
+                        return -1;
+                }
+        }
+        nlines = i;
+
+        if (!device_name || !nlines) {
+                print_usage();
+                return -1;
+        }
+        return hammer_device(device_name, lines, nlines, loops);
+}