gpio: add userspace ABI for GPIO line information

This adds a GPIO line ABI for getting name, label and a few select
flags from the kernel.

This hides the kernel internals and only tells userspace what it
may need to know: the different in-kernel consumers are masked
behind the flag "kernel" and that is all userspace needs to know.

However electric characteristics like active low, open drain etc
are reflected to userspace, as this is important information.

We provide information on all lines on all chips, later on we will
likely add a flag for the chardev consumer so we can filter and
display only the lines userspace actually uses in e.g. lsgpio,
but then we first need an ABI for userspace to grab and use
(get/set/select direction) a GPIO line.

Sample output from "lsgpio" on ux500:

GPIO chip: gpiochip7, "8011e000.gpio", 32 GPIO lines
        line 0: unnamed unlabeled
        line 1: unnamed unlabeled
(...)
        line 25: unnamed "SFH7741 Proximity Sensor" [kernel output open-drain]
        line 26: unnamed unlabeled
(...)

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

2 files changed, 81 insertions, 12 deletions

diff --git a/tools/gpio/gpio-utils.h b/tools/gpio/gpio-utils.h
index b18209a..5f57133 100644
--- a/tools/gpio/gpio-utils.h
+++ b/tools/gpio/gpio-utils.h
@@ -16,6 +16,8 @@
 
 #include <string.h>
 
+#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+
 static inline int check_prefix(const char *str, const char *prefix)
 {
 	return strlen(str) > strlen(prefix) &&
diff --git a/tools/gpio/lsgpio.c b/tools/gpio/lsgpio.c
index 692233f..5535ce8 100644
--- a/tools/gpio/lsgpio.c
+++ b/tools/gpio/lsgpio.c
@@ -26,12 +26,56 @@
 
 #include "gpio-utils.h"
 
+struct gpio_flag {
+	char *name;
+	unsigned long mask;
+};
+
+struct gpio_flag flagnames[] = {
+	{
+		.name = "kernel",
+		.mask = GPIOLINE_FLAG_KERNEL,
+	},
+	{
+		.name = "output",
+		.mask = GPIOLINE_FLAG_IS_OUT,
+	},
+	{
+		.name = "active-low",
+		.mask = GPIOLINE_FLAG_ACTIVE_LOW,
+	},
+	{
+		.name = "open-drain",
+		.mask = GPIOLINE_FLAG_OPEN_DRAIN,
+	},
+	{
+		.name = "open-source",
+		.mask = GPIOLINE_FLAG_OPEN_SOURCE,
+	},
+};
+
+void print_flags(unsigned long flags)
+{
+	int i;
+	int printed = 0;
+
+	for (i = 0; i < ARRAY_SIZE(flagnames); i++) {
+		if (flags & flagnames[i].mask) {
+			if (printed)
+				fprintf(stdout, " ");
+			fprintf(stdout, "%s", flagnames[i].name);
+			printed++;
+		}
+	}
+}
+
 int list_device(const char *device_name)
 {
 	struct gpiochip_info cinfo;
 	char *chrdev_name;
 	int fd;
 	int ret;
+	int i;
 
 	ret = asprintf(&chrdev_name, "/dev/%s", device_name);
 	if (ret < 0)
@@ -41,32 +85,55 @@ int list_device(const char *device_name)
 	if (fd == -1) {
 		ret = -errno;
 		fprintf(stderr, "Failed to open %s\n", chrdev_name);
-		goto free_chrdev_name;
+		goto exit_close_error;
 	}
 
 	/* Inspect this GPIO chip */
 	ret = ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &cinfo);
 	if (ret == -1) {
 		ret = -errno;
-		fprintf(stderr, "Failed to retrieve GPIO fd\n");
-		if (close(fd) == -1)
-			perror("Failed to close GPIO character device file");
-
-		goto free_chrdev_name;
+		perror("Failed to issue CHIPINFO IOCTL\n");
+		goto exit_close_error;
 	}
 	fprintf(stdout, "GPIO chip: %s, \"%s\", %u GPIO lines\n",
 		cinfo.name, cinfo.label, cinfo.lines);
 
-	if (close(fd) == -1)  {
-		ret = -errno;
-		goto free_chrdev_name;
+	/* Loop over the lines and print info */
+	for (i = 0; i < cinfo.lines; i++) {
+		struct gpioline_info linfo;
+
+		memset(&linfo, 0, sizeof(linfo));
+		linfo.line_offset = i;
+
+		ret = ioctl(fd, GPIO_GET_LINEINFO_IOCTL, &linfo);
+		if (ret == -1) {
+			ret = -errno;
+			perror("Failed to issue LINEINFO IOCTL\n");
+			goto exit_close_error;
+		}
+		fprintf(stdout, "\tline %d:", linfo.line_offset);
+		if (linfo.name[0])
+			fprintf(stdout, " %s", linfo.name);
+		else
+			fprintf(stdout, " unnamed");
+		if (linfo.label[0])
+			fprintf(stdout, " \"%s\"", linfo.label);
+		else
+			fprintf(stdout, " unlabeled");
+		if (linfo.flags) {
+			fprintf(stdout, " [");
+			print_flags(linfo.flags);
+			fprintf(stdout, "]");
+		}
+		fprintf(stdout, "\n");
+
 	}
 
-free_chrdev_name:
+exit_close_error:
+	if (close(fd) == -1)
+		perror("Failed to close GPIO character device file");
 	free(chrdev_name);
-
 	return ret;
-
 }
 
 void print_usage(void)