autoload i2c-dev module when needed

autoload i2c-dev module when needed

[Michal Minář]

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Hello,

we've got following request (viz [1]):

i2cdetect requires the i2c-dev module be loaded so the appropriate
/dev entries are created. This is not done automatically, so when
i2cdetect is initially run it gives the false impression that no
buses/devices exist:

# i2cdetect -l
# modprobe i2c-dev
# i2cdetect -l
i2c-0	i2c       	i915 gmbus ssc                  	I2C adapter
i2c-1	i2c       	i915 gmbus vga                  	I2C adapter
i2c-2	i2c       	i915 gmbus panel                	I2C adapter
i2c-3	i2c       	i915 gmbus dpc                  	I2C adapter
i2c-4	i2c       	i915 gmbus dpb                  	I2C adapter
i2c-5	i2c       	i915 gmbus dpd                  	I2C adapter
i2c-6	i2c       	DPDDC-C                         	I2C adapter
i2c-7	i2c       	DPDDC-D                         	I2C adapter


Attached is a patch that autoloads i2c-dev module when neccessary. If
you like it and have commit rights, push it please instead of me. If
you don't like it, don't hold back and tell me.

Best regards,
Michal Minar

[1] https://bugzilla.redhat.com/show_bug.cgi?id=913203
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Index: i2c-tools-3.1.0/tools/i2cbusses.c
===================================================================
--- i2c-tools-3.1.0.orig/tools/i2cbusses.c
+++ i2c-tools-3.1.0/tools/i2cbusses.c
@@ -37,9 +37,15 @@
 #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 512
+#define I2C_DEV_MOD_NAME "i2c_dev"
+
 enum adt { adt_dummy, adt_isa, adt_i2c, adt_smbus, adt_unknown };
 
 struct adap_type {
@@ -60,6 +66,70 @@ static struct adap_type adap_types[5] =
 	  .algo		= "N/A", },
 };
 
+/**
+ * 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);
+	}
+
+list_unref:
+	kmod_module_unref_list(list);
+ctx_unref:
+	kmod_unref(ctx);
+#else
+	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;
+	}
+#endif
+	if (errbuf[0])
+		fprintf(stderr, "Failed to load required " I2C_DEV_MOD_NAME
+			   	" kernel module: %s\n", errbuf);
+done:
+	return loaded;
+}
+
 static enum adt i2c_get_funcs(int i2cbus)
 {
 	unsigned long funcs;
@@ -206,8 +276,12 @@ struct i2c_adap *gather_i2c_busses(void)
 	   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, "."))
Index: i2c-tools-3.1.0/tools/Module.mk
===================================================================
--- i2c-tools-3.1.0.orig/tools/Module.mk
+++ i2c-tools-3.1.0/tools/Module.mk
@@ -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
 #

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Re: autoload i2c-dev module when needed

[Wolfram Sang]

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Adding Jean Delvare who maintains i2c-tools to CC...

On Thu, Jun 05, 2014 at 10:17:33AM +0200, Michal Minář wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Hello,
> 
> we've got following request (viz [1]):
> 
> i2cdetect requires the i2c-dev module be loaded so the appropriate
> /dev entries are created. This is not done automatically, so when
> i2cdetect is initially run it gives the false impression that no
> buses/devices exist:
> 
> # i2cdetect -l
> # modprobe i2c-dev
> # i2cdetect -l
> i2c-0	i2c       	i915 gmbus ssc                  	I2C adapter
> i2c-1	i2c       	i915 gmbus vga                  	I2C adapter
> i2c-2	i2c       	i915 gmbus panel                	I2C adapter
> i2c-3	i2c       	i915 gmbus dpc                  	I2C adapter
> i2c-4	i2c       	i915 gmbus dpb                  	I2C adapter
> i2c-5	i2c       	i915 gmbus dpd                  	I2C adapter
> i2c-6	i2c       	DPDDC-C                         	I2C adapter
> i2c-7	i2c       	DPDDC-D                         	I2C adapter
> 
> 
> Attached is a patch that autoloads i2c-dev module when neccessary. If
> you like it and have commit rights, push it please instead of me. If
> you don't like it, don't hold back and tell me.
> 
> Best regards,
> Michal Minar
> 
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=913203
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1
> Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/
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> Index: i2c-tools-3.1.0/tools/i2cbusses.c
> ===================================================================
> --- i2c-tools-3.1.0.orig/tools/i2cbusses.c
> +++ i2c-tools-3.1.0/tools/i2cbusses.c
> @@ -37,9 +37,15 @@
>  #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 512
> +#define I2C_DEV_MOD_NAME "i2c_dev"
> +
>  enum adt { adt_dummy, adt_isa, adt_i2c, adt_smbus, adt_unknown };
>  
>  struct adap_type {
> @@ -60,6 +66,70 @@ static struct adap_type adap_types[5] =
>  	  .algo		= "N/A", },
>  };
>  
> +/**
> + * 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);
> +	}
> +
> +list_unref:
> +	kmod_module_unref_list(list);
> +ctx_unref:
> +	kmod_unref(ctx);
> +#else
> +	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;
> +	}
> +#endif
> +	if (errbuf[0])
> +		fprintf(stderr, "Failed to load required " I2C_DEV_MOD_NAME
> +			   	" kernel module: %s\n", errbuf);
> +done:
> +	return loaded;
> +}
> +
>  static enum adt i2c_get_funcs(int i2cbus)
>  {
>  	unsigned long funcs;
> @@ -206,8 +276,12 @@ struct i2c_adap *gather_i2c_busses(void)
>  	   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, "."))
> Index: i2c-tools-3.1.0/tools/Module.mk
> ===================================================================
> --- i2c-tools-3.1.0.orig/tools/Module.mk
> +++ i2c-tools-3.1.0/tools/Module.mk
> @@ -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
>  #



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Re: autoload i2c-dev module when needed

[Michal Minář]

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Hash: SHA1

Thanks Dan!

Updated and a bit refactored patch is attached.

Michal
On 07/17/2014 02:56 AM, Danielle Costantino wrote:
> you need to add this after the #else , before the err = system...
> to accommodate for systems that have i2c-dev.ko built in, not as a
> module, on older kernels.
> 
> struct stat st;
> 
> err = stat("/sys/class/i2c-dev", &st);
> 
> if (err < 0) { if (errno != ENOENT) { err = -errno; goto done; }
> else err = 0; } else return 1;
> 
> 
> 
> On Wed, Jul 16, 2014 at 10:14 AM, Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
> wrote:
> 
>> 
>> Adding Jean Delvare who maintains i2c-tools to CC...
>> 
>> On Thu, Jun 05, 2014 at 10:17:33AM +0200, Michal Minář wrote:
> Hello,
> 
> we've got following request (viz [1]):
> 
> i2cdetect requires the i2c-dev module be loaded so the appropriate 
> /dev entries are created. This is not done automatically, so when 
> i2cdetect is initially run it gives the false impression that no 
> buses/devices exist:
> 
> # i2cdetect -l # modprobe i2c-dev # i2cdetect -l i2c-0 i2c
> i915 gmbus ssc                          I2C adapter i2c-1 i2c
> i915 gmbus vga                          I2C adapter i2c-2 i2c
> i915 gmbus panel                        I2C adapter i2c-3 i2c
> i915 gmbus dpc                          I2C adapter i2c-4 i2c
> i915 gmbus dpb                          I2C adapter i2c-5 i2c
> i915 gmbus dpd                          I2C adapter i2c-6 i2c
> DPDDC-C                                 I2C adapter i2c-7 i2c
> DPDDC-D                                 I2C adapter
> 
> 
> Attached is a patch that autoloads i2c-dev module when neccessary.
> If you like it and have commit rights, push it please instead of
> me. If you don't like it, don't hold back and tell me.
> 
> Best regards, Michal Minar
> 
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=913203
>> 
>>> Index: i2c-tools-3.1.0/tools/i2cbusses.c 
>>> ===================================================================
>>>
>>> 
- --- i2c-tools-3.1.0.orig/tools/i2cbusses.c
>>> +++ i2c-tools-3.1.0/tools/i2cbusses.c @@ -37,9 +37,15 @@ 
>>> #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 512 +#define I2C_DEV_MOD_NAME "i2c_dev" + enum
>>> adt { adt_dummy, adt_isa, adt_i2c, adt_smbus, adt_unknown };
>>> 
>>> struct adap_type { @@ -60,6 +66,70 @@ static struct adap_type
>>> adap_types[5] = .algo         = "N/A", }, };
>>> 
>>> +/** + * 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); +
>>> } + +list_unref: +     kmod_module_unref_list(list); 
>>> +ctx_unref: +     kmod_unref(ctx); +#else +     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; +     } 
>>> +#endif +     if (errbuf[0]) +             fprintf(stderr,
>>> "Failed to load required " I2C_DEV_MOD_NAME +
>>> " kernel module: %s\n", errbuf); +done: +     return loaded; 
>>> +} + static enum adt i2c_get_funcs(int i2cbus) { unsigned long
>>> funcs; @@ -206,8 +276,12 @@ struct i2c_adap
>>> *gather_i2c_busses(void) 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, ".")) Index:
>>> i2c-tools-3.1.0/tools/Module.mk 
>>> ===================================================================
>>>
>>> 
- --- i2c-tools-3.1.0.orig/tools/Module.mk
>>> +++ i2c-tools-3.1.0/tools/Module.mk @@ -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 #
>> 
>> 
>> 
> 
> 

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Index: i2c-tools/tools/i2cbusses.c
===================================================================
--- i2c-tools.orig/tools/i2cbusses.c
+++ i2c-tools/tools/i2cbusses.c
@@ -38,10 +38,17 @@
 #include <dirent.h>
 #include <fcntl.h>
 #include <errno.h>
+#ifdef USE_LIBKMOD
+	#include <libkmod.h>
+#endif
 #include "i2cbusses.h"
 #include <linux/i2c.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 {
@@ -62,6 +69,142 @@ 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:
+	return loaded;
+}
+
 static enum adt i2c_get_funcs(int i2cbus)
 {
 	unsigned long funcs;
@@ -134,8 +277,7 @@ 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;
 
@@ -187,29 +329,19 @@ 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, "."))
@@ -274,14 +406,15 @@ 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;
@@ -291,6 +424,7 @@ found:
 	closedir(dir);
 
 done:
+	free(sysfs);
 	return adapters;
 }
 
Index: i2c-tools/tools/Module.mk
===================================================================
--- i2c-tools.orig/tools/Module.mk
+++ i2c-tools/tools/Module.mk
@@ -16,6 +16,11 @@ TOOLS_LDFLAGS	:= -Llib -li2c
 
 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
 #

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Re: autoload i2c-dev module when needed

[Wolfram Sang]

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> Updated and a bit refactored patch is attached.

Ping Jean if you are still interested in this patch. He is maintaining
the i2c-tools. I'll mark it as deferred for now.


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