[PATCH evtest 2/2] Add one-shot query functionality

Daniel Drake dsd at laptop.org
Thu Jul 14 09:53:17 PDT 2011


Add functionality to query evdev state of a specific key, switch, button,
LED or sound event. This is useful in programs such as powerd
(http://wiki.laptop.org/go/Powerd) which need to query things like the
state of the laptop lid switch from shell code.

Original monitor-mode functionality is left unchanged and is still
activated by default. New usage modes are explained in the man page.

Signed-off-by: Daniel Drake <dsd at laptop.org>
---
 evtest.c   |  267 ++++++++++++++++++++++++++++++++++++++++++++++++++++--------
 evtest.txt |   31 ++++++-
 2 files changed, 257 insertions(+), 41 deletions(-)

diff --git a/evtest.c b/evtest.c
index 5cc8505..39e403f 100644
--- a/evtest.c
+++ b/evtest.c
@@ -49,6 +49,8 @@
 #include <stdlib.h>
 #include <dirent.h>
 #include <errno.h>
+#include <getopt.h>
+#include <ctype.h>
 
 #define BITS_PER_LONG (sizeof(long) * 8)
 #define NBITS(x) ((((x)-1)/BITS_PER_LONG)+1)
@@ -56,6 +58,7 @@
 #define BIT(x)  (1UL<<OFF(x))
 #define LONG(x) ((x)/BITS_PER_LONG)
 #define test_bit(bit, array)	((array[LONG(bit)] >> OFF(bit)) & 1)
+#define ARRAY_SIZE(i) (sizeof(i) / sizeof(*i))
 
 #define DEV_INPUT_EVENT "/dev/input"
 #define EVENT_DEV_NAME "event"
@@ -69,6 +72,14 @@
 
 #define NAME_ELEMENT(element) [element] = #element
 
+enum evtest_mode {
+	MODE_GRAB,
+	MODE_QUERY_SW,
+	MODE_QUERY_KEY,
+	MODE_QUERY_LED,
+	MODE_QUERY_SND,
+};
+
 static const char * const events[EV_MAX + 1] = {
 	[0 ... EV_MAX] = NULL,
 	NAME_ELEMENT(EV_SYN),			NAME_ELEMENT(EV_KEY),
@@ -480,6 +491,68 @@ static const char * const * const names[EV_MAX + 1] = {
 };
 
 /**
+ * Search for the code of a specific key/snd/led/sw bit, based on its textual
+ * representation (e.g. SW_DOCK).
+ *
+ * @param type The EV_ event type being queried
+ * @param kstr The string to parse and convert
+ *
+ * @return The requested code's numerical value, or negative on error.
+ */
+static int key_name_to_code(int type, int max, const char *kstr)
+{
+	const char * const *keynames = names[type];
+	int i;
+
+	for (i = 0; i < max; i++) {
+		const char *name = keynames[i];
+		if (!name)
+			continue;
+		if (strcasecmp(name, kstr) == 0)
+			return i;
+	}
+
+	return -1;
+}
+
+/**
+ * Convert a string to a specific key/snd/led/sw code. The string can either
+ * be the name of the key in question (e.g. "SW_CODE") or the numerical
+ * value, either as decimal (e.g. "5") or as hex (e.g. "0x5").
+ *
+ * @param mode The mode being queried (key, snd, led, sw)
+ * @param kstr The string to parse and convert
+ *
+ * @return The requested code's numerical value, or negative on error.
+ */
+static int get_keycode(enum evtest_mode mode, const char *kstr)
+{
+	if (isdigit(kstr[0])) {
+		unsigned long val;
+		errno = 0;
+		val = strtoul(kstr, NULL, 0);
+		if (errno) {
+			fprintf(stderr, "Could not interpret value %s\n", kstr);
+			return -1;
+		}
+		return (int) val;
+	}
+
+	switch (mode) {
+	case MODE_QUERY_SW:
+		return key_name_to_code(EV_SW, SW_CNT, kstr);
+	case MODE_QUERY_KEY:
+		return key_name_to_code(EV_KEY, KEY_CNT, kstr);
+	case MODE_QUERY_SND:
+		return key_name_to_code(EV_SND, SND_CNT, kstr);
+	case MODE_QUERY_LED:
+		return key_name_to_code(EV_LED, LED_CNT, kstr);
+	}
+
+	return -1;
+}
+
+/**
  * Filter for the AutoDevProbe scandir on /dev/input.
  *
  * @param dir The current directory entry provided by scandir.
@@ -544,38 +617,26 @@ static char* scan_devices(void)
 /**
  * Print usage information.
  */
-static void usage(void)
+static void __attribute__((noreturn)) usage(void)
 {
-	printf("Usage: evtest /dev/input/eventX\n");
-	printf("Where X = input device number\n");
-}
-
-/**
- * Parse the commandline arguments.
- *
- * @return The filename of the device file to open, or NULL in case of
- * error. This string is allocated and must be freed by the caller.
- */
-static char* parse_args(int argc, char **argv)
-{
-	char *filename;
-
-	if (argc < 2) {
-		fprintf(stderr, "No device specified, trying to scan all of %s/%s*\n",
-			DEV_INPUT_EVENT, EVENT_DEV_NAME);
-
-		if (getuid() != 0)
-			fprintf(stderr, "Not running as root, no devices may be available.\n");
-
-		filename = scan_devices();
-		if (!filename) {
-			usage();
-			return NULL;
-		}
-	} else
-		filename = strdup(argv[argc - 1]);
-
-	return filename;
+	printf("USAGE:\n");
+	printf(" Grab mode:\n");
+	printf("   %s /dev/input/eventX\n", program_invocation_short_name);
+	printf("\n");
+	printf(" Query mode: (check exit code)\n");
+	printf("   %s --query-sw <value> /dev/input/eventX\n",
+		program_invocation_short_name);
+	printf("   %s --query-key <value> /dev/input/eventX\n",
+		program_invocation_short_name);
+	printf("   %s --query-led <value> /dev/input/eventX\n",
+		program_invocation_short_name);
+	printf("   %s --query-snd <value> /dev/input/eventX\n",
+		program_invocation_short_name);
+
+	printf("\n");
+	printf("<value> can either be a numerical value, or the textual name of the\n");
+	printf("key/switch/LED/sound being queried (e.g. SW_DOCK).\n");
+	_exit(EXIT_FAILURE);
 }
 
 /**
@@ -708,17 +769,42 @@ static int test_grab(int fd)
 	return rc;
 }
 
-int main (int argc, char **argv)
+static const struct option long_options[] = {
+	{ "query-sw", required_argument, NULL, MODE_QUERY_SW },
+	{ "query-snd", required_argument, NULL, MODE_QUERY_SND },
+	{ "query-key", required_argument, NULL, MODE_QUERY_KEY },
+	{ "query-led", required_argument, NULL, MODE_QUERY_LED },
+	{ 0, },
+};
+
+/**
+ * Enter grab mode. The requested event device will be grabbed and any
+ * captured events will be decoded and printed on the console.
+ *
+ * @param device The device to grab, or NULL if the user should be prompted.
+ * @return 0 on success, non-zero on error.
+ */
+static int do_grab(const char *device)
 {
 	int fd;
 	char *filename;
 
-	filename = parse_args(argc, argv);
+	if (device) {
+		filename = strdup(device);
+	} else {
+		fprintf(stderr, "No device specified, trying to scan all of %s/%s*\n",
+			DEV_INPUT_EVENT, EVENT_DEV_NAME);
 
-	if (!filename)
-		return 1;
+		if (getuid() != 0)
+			fprintf(stderr, "Not running as root, no devices may be available.\n");
 
-	if ((fd = open(filename, O_RDONLY)) < 0) {
+		filename = scan_devices();
+		if (!filename)
+			usage();
+	}
+
+	fd = open(filename, O_RDONLY);
+	if (fd < 0) {
 		perror("evtest");
 		if (errno == EACCES && getuid() != 0)
 			fprintf(stderr, "You do not have access to %s. Try "
@@ -751,4 +837,113 @@ int main (int argc, char **argv)
 	return print_events(fd);
 }
 
+/**
+ * Enter query mode. The requested event device will be queried for the state
+ * of a particular switch/key/sound/LED.
+ *
+ * @param device The device to query.
+ * @param mode The mode (event type) that is to be queried (snd, sw, key, led)
+ * @param keycode The key code to query the state of.
+ * @return 0 if the state bit is unset, 10 if the state bit is set.
+ */
+static int do_query(const char *device, enum evtest_mode mode, int keycode)
+{
+	int rq;
+	int max;
+	int fd;
+	int r;
+
+	switch (mode) {
+	case MODE_QUERY_SW:
+		max = SW_MAX;
+		rq = EVIOCGSW(SW_MAX);
+		break;
+	case MODE_QUERY_KEY:
+		max = KEY_MAX;
+		rq = EVIOCGKEY(KEY_MAX);
+		break;
+	case MODE_QUERY_SND:
+		max = SND_MAX;
+		rq = EVIOCGSND(SND_MAX);
+		break;
+	case MODE_QUERY_LED:
+		max = SND_MAX;
+		rq = EVIOCGLED(LED_MAX);
+		break;
+	}
+
+	if (keycode > max) {
+		fprintf(stderr, "Key 0x%x out of bounds.\n", keycode);
+		_exit(EXIT_FAILURE);
+	}
+
+	unsigned char state[NBITS(max)];
+
+	fd = open(device, O_RDONLY);
+	if (fd < 0) {
+		perror("open");
+		_exit(EXIT_FAILURE);
+	}
+
+	memset(state, 0, sizeof(state));
+	r = ioctl(fd, rq, state);
+	close(fd);
+
+	if (r == -1) {
+		perror("ioctl");
+		_exit(EXIT_FAILURE);
+	}
+
+	if (test_bit(keycode, state))
+		return 10; /* different from EXIT_FAILURE */
+	else
+		return 0;
+}
+
+int main (int argc, char **argv)
+{
+	const char *device = NULL;
+	const char *keyname;
+	enum evtest_mode mode = MODE_GRAB;
+	int keycode;
+
+	while (1) {
+		int option_index = 0;
+		int c = getopt_long(argc, argv, "", long_options, &option_index);
+		if (c == -1)
+			break;
+		switch (c) {
+		case MODE_QUERY_SW:
+		case MODE_QUERY_KEY:
+		case MODE_QUERY_LED:
+		case MODE_QUERY_SND:
+			mode = c;
+			keyname = optarg;
+			keycode = get_keycode(mode, keyname);
+			break;
+		default:
+			usage();
+			break;
+		}
+	}
+
+	if (optind < argc)
+		device = argv[optind++];
+
+	if (mode == MODE_GRAB)
+		return do_grab(device);
+
+	if (keycode < 0) {
+		fprintf(stderr, "Unrecognised key name: %s\n", keyname);
+		usage();
+	}
+
+	if (!device) {
+		fprintf(stderr, "Device argument is required for query.\n");
+		usage();
+	}
+
+	return do_query(device, mode, keycode);
+}
+
 /* vim: set noexpandtab tabstop=8 shiftwidth=8: */
diff --git a/evtest.txt b/evtest.txt
index 685a4de..f255edd 100644
--- a/evtest.txt
+++ b/evtest.txt
@@ -4,17 +4,31 @@ EVTEST(1)
 NAME
 ----
 
-     evtest - Input device event monitor
+     evtest - Input device event monitor and query tool
 
 SYNOPSIS
 --------
-     evtest "/dev/input/eventX"
+     evtest /dev/input/eventX
+
+     evtest --query-sw <value> /dev/input/eventX
+     evtest --query-key <value> /dev/input/eventX
+     evtest --query-snd <value> /dev/input/eventX
+     evtest --query-led <value> /dev/input/eventX
 
 DESCRIPTION
 -----------
-evtest displays information on the input device specified on the command
-line, including all the events supported by the device. It then monitors the
-device and displays all the events layer events generated.
+The first invocation type displayed above causes evtest to display
+information about the specified input device, including all the events
+supported by the device. It then monitors the device and displays all the
+events layer events generated.
+
+In the other 4 invocation types, evtest performs a one-shot query of the state
+of a specific switch (sw), key, sound (snd) or LED, specified by *value*. If
+the state bit is set (key pressed, switch on, ...), evtest exits with
+code 0. If the state bit is unset (key depressed, switch off, ...), evtest
+exits with code 10. No other output is generated. *value* can be either a
+decimal representation (e.g. 44), hex (e.g. 0x2c), or the constant name (e.g.
+KEY_Z).
 
 evtest needs to be able to read from the device; in most cases this means it
 must be run as root.
@@ -32,6 +46,13 @@ when debugging a synaptics device from within X. VT switching to a TTY or
 shutting down the X server terminates this grab and synaptics devices can be
 debugged.
 
+EXIT CODE
+---------
+evtest returns 1 on error.
+
+When used to query state, evtest returns 0 if the state bit is unset and
+10 if the state bit is set.
+
 SEE ALSO
 --------
 inputattach(1)
-- 
1.7.6



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