[libgpiod PATCH] gpioget: Add --line-name to lookup GPIO line

[Joel Stanley]

Systems provide line names to make using GPIOs easier for userspace. Use
this feature to make the tools user friendly by adding the ability to
show the state of a named line.

 $ gpioget --line-name power-chassis-good
 1

 $ gpioget -L pcieslot-power
 0

Signed-off-by: Joel Stanley <joel at jms.id.au>
---
While users do have the ability to chain together gpioinfo and gpioget,
this is less discoverable for people new to the tools, and harder to
explain to eg. technicians, and requires more typing.

Please consider this enhancement. If you are happy with it I can send
a patch for gpioset too.

Signed-off-by: Joel Stanley <joel at jms.id.au>
---
 tools/gpioget.c | 86 ++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 64 insertions(+), 22 deletions(-)

diff --git a/tools/gpioget.c b/tools/gpioget.c
index 51cecb6a18a9..cd27320b7f2b 100644
--- a/tools/gpioget.c
+++ b/tools/gpioget.c
@@ -6,6 +6,7 @@
 #include <limits.h>
 #include <stdio.h>
 #include <string.h>
+#include <errno.h>
 
 #include "tools-common.h"
 
@@ -18,7 +19,7 @@ static const struct option longopts[] = {
 	{ GETOPT_NULL_LONGOPT },
 };
 
-static const char *const shortopts = "+hvlnB:";
+static const char *const shortopts = "+hvlnB:L:";
 
 static void print_help(void)
 {
@@ -34,6 +35,7 @@ static void print_help(void)
 	printf("  -n, --dir-as-is:\tdon't force-reconfigure line direction\n");
 	printf("  -B, --bias=[as-is|disable|pull-down|pull-up] (defaults to 'as-is'):\n");
 	printf("		set the line bias\n");
+	printf("  -L, --line-name:\tUse this GPIO line (instead of chip name and offset)\n");
 	printf("\n");
 	print_bias_help();
 }
@@ -47,6 +49,7 @@ int main(int argc, char **argv)
 	struct gpiod_line_bulk *lines;
 	struct gpiod_chip *chip;
 	char *device, *end;
+	char *name = NULL;
 
 	for (;;) {
 		optc = getopt_long(argc, argv, shortopts, longopts, &opti);
@@ -69,8 +72,13 @@ int main(int argc, char **argv)
 		case 'B':
 			flags |= bias_flags(optarg);
 			break;
+		case 'L':
+			name = optarg;
+			num_lines = 1;
+			break;
 		case '?':
 			die("try %s --help", get_progname());
+			break;
 		default:
 			abort();
 		}
@@ -79,30 +87,64 @@ int main(int argc, char **argv)
 	argc -= optind;
 	argv += optind;
 
-	if (argc < 1)
-		die("gpiochip must be specified");
-
-	if (argc < 2)
-		die("at least one GPIO line offset must be specified");
-
-	device = argv[0];
-	num_lines = argc - 1;
-
-	values = malloc(sizeof(*values) * num_lines);
-	offsets = malloc(sizeof(*offsets) * num_lines);
-	if (!values || !offsets)
-		die("out of memory");
+	if (name) {
+		struct dirent **entries;
+		unsigned int num_chips;
+		int offset, n;
+
+		n = scandir("/dev/", &entries, chip_dir_filter, alphasort);
+		if (n < 0)
+			die_perror("unable to scan /dev");
+		num_chips = n;
+
+		values = malloc(sizeof(*values) * 1);
+		offsets = malloc(sizeof(*offsets) * 1);
+		if (!values || !offsets)
+			die("out of memory");
+
+		for (i = 0; i < num_chips; i++) {
+			device = entries[i]->d_name;
+			chip = chip_open_by_name(device);
+			if (!chip) {
+				if (errno == EACCES)
+					continue;
+
+				die_perror("unable to open %s", device);
+			}
+			offset = gpiod_chip_find_line(chip, name);
+			if (offset >= 0) {
+				offsets[0] = offset;
+				break;
+			}
+		}
+		if (i == num_chips)
+			die("unable to find line '%s'", name);
+	} else {
+		if (argc < 1)
+			die("gpiochip must be specified");
+
+		if (argc < 2)
+			die("at least one GPIO line offset must be specified");
+
+		device = argv[0];
+		num_lines = argc - 1;
+
+		values = malloc(sizeof(*values) * num_lines);
+		offsets = malloc(sizeof(*offsets) * num_lines);
+		if (!values || !offsets)
+			die("out of memory");
+
+		for (i = 0; i < num_lines; i++) {
+			offsets[i] = strtoul(argv[i + 1], &end, 10);
+			if (*end != '\0' || offsets[i] > INT_MAX)
+				die("invalid GPIO offset: %s", argv[i + 1]);
+		}
 
-	for (i = 0; i < num_lines; i++) {
-		offsets[i] = strtoul(argv[i + 1], &end, 10);
-		if (*end != '\0' || offsets[i] > INT_MAX)
-			die("invalid GPIO offset: %s", argv[i + 1]);
+		chip = chip_open_lookup(device);
+		if (!chip)
+			die_perror("unable to open %s", device);
 	}
 
-	chip = chip_open_lookup(device);
-	if (!chip)
-		die_perror("unable to open %s", device);
-
 	lines = gpiod_chip_get_lines(chip, offsets, num_lines);
 	if (!lines)
 		die_perror("unable to retrieve GPIO lines from chip");
-- 
2.33.0