diff -up i2c-tools-3.1.0/tools/i2cbusses.c.load-i2cdev i2c-tools-3.1.0/tools/i2cbusses.c

--- i2c-tools-3.1.0/tools/i2cbusses.c.load-i2cdev	2010-11-26 11:25:32.000000000 +0100

+++ i2c-tools-3.1.0/tools/i2cbusses.c	2017-04-05 08:43:08.135938481 +0200

@@ -37,9 +37,16 @@

 #include <dirent.h>

 #include <fcntl.h>

 #include <errno.h>

+#ifdef USE_LIBKMOD

+	#include <libkmod.h>

+#endif

 #include "i2cbusses.h"

 #include <linux/i2c-dev.h>

+#define BUFLEN (NAME_MAX > 512 ? NAME_MAX : 512)

+#define I2C_DEV_MOD_NAME "i2c_dev"

+#define I2C_DEV_SUBPATH  "/class/i2c-dev"

+

 enum adt { adt_dummy, adt_isa, adt_i2c, adt_smbus, adt_unknown };

 struct adap_type {

@@ -60,6 +67,145 @@ static struct adap_type adap_types[5] =

 	  .algo		= "N/A", },

 };

+/* Get and cache sysfs mount point. */

+static const char *get_sysfs_mount_point(void) {

+	static const char *mp = NULL;

+

+	if (mp == NULL) {

+		char sysfs[NAME_MAX];

+		char fstype[NAME_MAX];

+		char line[BUFLEN];

+		FILE *f;

+

+		if ((f = fopen("/proc/mounts", "r")) == NULL) {

+			perror("failed to read /proc/mounts: ");

+			goto done;

+		}

+		while (fgets(line, BUFLEN, f)) {

+			sscanf(line, "%*[^ ] %[^ ] %[^ ] %*s\n", sysfs, fstype);

+			if (strcasecmp(fstype, "sysfs") == 0) {

+				mp = strdup(sysfs);

+				if (mp == NULL)

+					perror("strdup: ");

+				break;

+			}

+		}

+		fclose(f);

+	}

+done:

+	return mp;

+}

+

+/* Get an absolute path of i2c device directory. Free the result when not

+ * needed. */

+static char *get_i2c_dev_path(void) {

+	char *path = NULL;

+	int mplen, splen;

+	const char *mp = get_sysfs_mount_point();

+

+	if (mp != NULL) {

+		mplen = strlen(mp);

+		splen = strlen(I2C_DEV_SUBPATH);

+		path = malloc(mplen + splen + 1);

+		if (path == NULL) {

+			perror("malloc: ");

+		} else {

+			strncpy(path, mp, mplen);

+			strncpy(path + mplen, I2C_DEV_SUBPATH, splen);

+			path[mplen+splen] = '\0';

+		}

+	}

+	return path;

+}

+

+/**

+ * Try to load i2c_dev kernel mode. Do nothing if module is already loaded.

+ * Returns 1 on success, 0 otherwise.

+ */

+static int try_load_i2c_dev_mod(void) {

+	int err = 0, loaded = 0;

+	char errbuf[BUFLEN] = { 0 };

+#ifdef USE_LIBKMOD

+	int flags = 0;

+	struct kmod_ctx *ctx;

+	struct kmod_list *l, *list = NULL;

+

+	ctx = kmod_new(NULL, NULL);

+	if (!ctx) {

+		snprintf(errbuf, BUFLEN, "kmod_new() failed!");

+		goto done;

+	}

+	if (kmod_module_new_from_lookup(ctx, I2C_DEV_MOD_NAME, &list) < 0 || list == NULL) {

+		snprintf(errbuf, BUFLEN, I2C_DEV_MOD_NAME " module lookup failed");

+		goto ctx_unref;

+	}

+

+	flags |= KMOD_PROBE_APPLY_BLACKLIST_ALIAS_ONLY;

+	kmod_list_foreach(l, list) {

+		struct kmod_module *mod = kmod_module_get_module(l);

+		err = kmod_module_probe_insert_module(mod, flags, NULL, NULL, NULL, NULL);

+		if (err == -ENOENT) {

+			snprintf(errbuf, BUFLEN,

+					"unknown symbol in module \"%s\", or unknown parameter (see dmesg)",

+					kmod_module_get_name(mod));

+		} else if (err < 0) {

+			snprintf(errbuf, BUFLEN, "(module %s): %s",

+					kmod_module_get_name(mod), strerror(-err));

+		} else {

+			kmod_module_unref(mod);

+			++loaded;

+			break;

+		}

+		kmod_module_unref(mod);

+	}

+

+	kmod_module_unref_list(list);

+ctx_unref:

+	kmod_unref(ctx);

+#else   /* Try to load the module with modprobe. */

+	struct stat st;

+	char *dev_path = get_i2c_dev_path();

+

+	/* First check whether the module is already loaded or built-in. */

+	if (dev_path == NULL)

+		goto done;

+	err = stat(dev_path, &st);

+	if (err < 0) {

+		if (errno != ENOENT) {

+			snprintf(errbuf, BUFLEN, "can not stat \"%s\": %s", dev_path,

+				   	strerror(errno));

+			goto err;

+		} else {

+			err = 0;

+		}

+	} else {

+		++loaded;

+		goto done;

+	}

+

+	err = system("modprobe " I2C_DEV_MOD_NAME);

+	if (err < 0) {

+		snprintf(errbuf, BUFLEN, "failed to execute modprobe command");

+	} else if (err > 0) {

+		snprintf(errbuf, BUFLEN, "modprobe command exited with code %d",

+				WEXITSTATUS(err));

+	} else {

+		++loaded;

+		goto done;

+	}

+

+err:

+#endif

+	if (errbuf[0])

+		fprintf(stderr, "Failed to load required " I2C_DEV_MOD_NAME

+			   	" kernel module: %s\n", errbuf);

+done:

+#ifndef USE_LIBKMOD

+	free(dev_path);

+#endif

+	return loaded;

+}

+

 static enum adt i2c_get_funcs(int i2cbus)

 {

 	unsigned long funcs;

@@ -132,8 +278,7 @@ struct i2c_adap *gather_i2c_busses(void)

 	struct dirent *de, *dde;

 	DIR *dir, *ddir;

 	FILE *f;

-	char fstype[NAME_MAX], sysfs[NAME_MAX], n[NAME_MAX];

-	int foundsysfs = 0;

+	char *sysfs = NULL, n[NAME_MAX];

 	int count=0;

 	struct i2c_adap *adapters;

@@ -185,29 +330,19 @@ struct i2c_adap *gather_i2c_busses(void)

 		goto done;

 	}

-	/* look in sysfs */

-	/* First figure out where sysfs was mounted */

-	if ((f = fopen("/proc/mounts", "r")) == NULL) {

+	sysfs = get_i2c_dev_path();

+	if (sysfs == NULL)

 		goto done;

-	}

-	while (fgets(n, NAME_MAX, f)) {

-		sscanf(n, "%*[^ ] %[^ ] %[^ ] %*s\n", sysfs, fstype);

-		if (strcasecmp(fstype, "sysfs") == 0) {

-			foundsysfs++;

-			break;

-		}

-	}

-	fclose(f);

-	if (! foundsysfs) {

-		goto done;

-	}

 	/* Bus numbers in i2c-adapter don't necessarily match those in

 	   i2c-dev and what we really care about are the i2c-dev numbers.

 	   Unfortunately the names are harder to get in i2c-dev */

-	strcat(sysfs, "/class/i2c-dev");

-	if(!(dir = opendir(sysfs)))

-		goto done;

+	if(!(dir = opendir(sysfs))) {

+		if (!try_load_i2c_dev_mod())

+			goto done;

+		if ((!(dir = opendir(sysfs))))

+			goto done;

+	}

 	/* go through the busses */

 	while ((de = readdir(dir)) != NULL) {

 		if (!strcmp(de->d_name, "."))

@@ -272,14 +407,15 @@ found:

 				/* We need more space */

 				adapters = more_adapters(adapters, count + 1);

 				if (!adapters)

-					return NULL;

+					goto done;

 			}

 			adapters[count].nr = i2cbus;

 			adapters[count].name = strdup(s);

 			if (adapters[count].name == NULL) {

 				free_adapters(adapters);

-				return NULL;

+				adapters = NULL;

+				goto done;

 			}

 			adapters[count].funcs = adap_types[type].funcs;

 			adapters[count].algo = adap_types[type].algo;

@@ -289,6 +425,7 @@ found:

 	closedir(dir);

 done:

+	free(sysfs);

 	return adapters;

 }

@@ -380,8 +517,21 @@ int open_i2c_dev(int i2cbus, char *filen

 	file = open(filename, O_RDWR);

 	if (file < 0 && (errno == ENOENT || errno == ENOTDIR)) {

+		if (!(try_load_i2c_dev_mod()))

+			fprintf(stderr, "Cannot load i2c-dev module.\n");

+		else

+			file = open(filename, O_RDWR);

+	}

+

+	if (file < 0 && (errno == ENOENT || errno == ENOTDIR)) {

 		sprintf(filename, "/dev/i2c-%d", i2cbus);

 		file = open(filename, O_RDWR);

+		if (file < 0 && (errno == ENOENT || errno == ENOTDIR)) {

+			if (!(try_load_i2c_dev_mod()))

+				fprintf(stderr, "Cannot load i2c-dev module.\n");

+			else

+				file = open(filename, O_RDWR);

+		}

 	}

 	if (file < 0 && !quiet) {

diff -up i2c-tools-3.1.0/tools/Module.mk.load-i2cdev i2c-tools-3.1.0/tools/Module.mk

--- i2c-tools-3.1.0/tools/Module.mk.load-i2cdev	2009-01-19 16:11:33.000000000 +0100

+++ i2c-tools-3.1.0/tools/Module.mk	2017-04-05 08:41:10.554057368 +0200

@@ -15,6 +15,11 @@ TOOLS_CFLAGS	:= -Wstrict-prototypes -Wsh

 TOOLS_TARGETS	:= i2cdetect i2cdump i2cset i2cget

+ifeq ($(shell pkg-config --exists libkmod && echo 1), 1)

+    TOOLS_CFLAGS  += $(shell pkg-config --cflags libkmod) -DUSE_LIBKMOD

+    LDFLAGS += $(shell pkg-config --libs libkmod)

+endif

+

 #

 # Programs

 #