Merge pull request #262 from vivien-consider-dropping-github/master

Dynamically get the udevadm hwdb files with a path variable

man/udev.7

@@ -540,13 +540,17 @@ character itself\&.
 The hwdb files are read from the files located in the system hwdb directory
 /usr/lib/udev/hwdb\&.d, the volatile runtime directory
 /run/udev/hwdb\&.d
-and the local administration directory
-/etc/udev/hwdb\&.d\&. All hwdb files are collectively sorted and processed in lexical order, regardless of the directories in which they live\&. However, files with identical filenames replace each other\&. Files in
+the local administration directory
+/etc/udev/hwdb\&.d, and any other directory in the
+\fBUDEV_HWDB_PATH\fR
+search path variable\&. All hwdb files are collectively sorted and processed in lexical order, regardless of the directories in which they live\&. However, files with identical filenames replace each other\&. Files in
 /etc
 have the highest priority, files in
 /run
 take precedence over files with the same name in
-/usr/lib\&. This can be used to override a system\-supplied hwdb file with a local file if needed; a symlink in
+/usr/lib, and the content of
+\fBUDEV_HWDB_PATH\fR
+comes last\&. This order can be used to override a system\-supplied hwdb file with a local file if needed; a symlink in
 /etc
 with the same name as a hwdb file in
 /usr/lib, pointing to

man/udev.xml

@@ -738,12 +738,15 @@
       <para>The hwdb files are read from the files located in the
       system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename>,
       the volatile runtime directory <filename>/run/udev/hwdb.d</filename>
-      and the local administration directory <filename>/etc/udev/hwdb.d</filename>.
+      the local administration directory <filename>/etc/udev/hwdb.d</filename>,
+      and any other directory in the <envar>UDEV_HWDB_PATH</envar> search path variable.
       All hwdb files are collectively sorted and processed in lexical order,
       regardless of the directories in which they live. However, files with
       identical filenames replace each other. Files in <filename>/etc</filename>
-      have the highest priority, files in <filename>/run</filename> take precedence
-      over files with the same name in <filename>/usr/lib</filename>. This can be
+      have the highest priority, files in <filename>/run</filename>
+      take precedence over files with the same name in
+      <filename>/usr/lib</filename>, and the content of
+      <envar>UDEV_HWDB_PATH</envar> comes last. This order can be
       used to override a system-supplied hwdb file with a local file if needed;
       a symlink in <filename>/etc</filename> with the same name as a hwdb file in
       <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,

man/udevadm.8

@@ -356,7 +356,11 @@ Maintain the hardware database index in
 .PP
 \fB\-u\fR, \fB\-\-update\fR
 .RS 4
-Compile the hardware database information located in /usr/lib/udev/hwdb\&.d/, /etc/udev/hwdb\&.d/ and store it in
+Compile the hardware database information located in
+/etc/udev/hwdb\&.d/,
+/usr/lib/udev/hwdb\&.d/, and under the
+\fBUDEV_HWDB_PATH\fR
+path environment variable, and store it in
 /etc/udev/hwdb\&.bin\&. This should be done after any update to the source files; it will not be called automatically\&. The running udev daemon will detect a new database on its own and does not need to be notified about it\&.
 .RE
 .PP

man/udevadm.xml

@@ -521,11 +521,16 @@
           <term><option>-u</option></term>
           <term><option>--update</option></term>
           <listitem>
-            <para>Compile the hardware database information located in /usr/lib/udev/hwdb.d/,
-            /etc/udev/hwdb.d/ and store it in <filename>/etc/udev/hwdb.bin</filename>. This should be done after
-            any update to the source files; it will not be called automatically. The running
-            udev daemon will detect a new database on its own and does not need to be
-            notified about it.</para>
+            <para>Compile the hardware database information located in
+            <filename>/etc/udev/hwdb.d/</filename>,
+            <filename>/usr/lib/udev/hwdb.d/</filename>, and under the
+            <envar>UDEV_HWDB_PATH</envar> path environment variable,
+            and store it in
+            <filename>/etc/udev/hwdb.bin</filename>. This should be
+            done after any update to the source files; it will not be
+            called automatically. The running udev daemon will detect
+            a new database on its own and does not need to be notified
+            about it.</para>
           </listitem>
         </varlistentry>
         <varlistentry>

src/shared/conf-files.c

@@ -143,3 +143,64 @@ int conf_files_list_strv(char ***strv, const char *suffix, const char *root, con
 
         return conf_files_list_strv_internal(strv, suffix, root, copy);
 }
+
+/* Copy every non-empty path element from path_variable to
+   destination, and add a final NULL pointer. If destination is NULL,
+   then only count the number of non-empty path elements. Return
+   -ENOMEM if the copy failed, or the number of elements. */
+static ssize_t conf_files_list_follow_path (const char *path_variable, char **destination) {
+        /* This function is not using strtok_r, because two passes are
+           required: the first one to count the number of elements,
+           the second one to actually copy them once an array of the
+           correct size has been allocated. */
+        size_t n = 0;
+        if (path_variable != NULL) {
+                while (path_variable[0] == ':') {
+                      path_variable++;
+                }
+                while (path_variable[0] != '\0') {
+                        const char *end = strchr(path_variable, ':');
+                        if (end == NULL) {
+                                end = path_variable + strlen(path_variable);
+                        }
+                        if (destination != NULL) {
+                                destination[n] = strndup(path_variable, end - path_variable);
+                                if (destination[n] == NULL) {
+                                        return -ENOMEM;
+                                }
+                        }
+                        n++;
+                        path_variable = end;
+                        while (path_variable[0] == ':') {
+                                path_variable++;
+                        }
+                }
+        }
+        if (destination != NULL) {
+                destination[n] = NULL;
+        }
+        return n;
+}
+
+/* path is a colon-separated list of directories. */
+int conf_files_list_strv_path(char ***strv, const char *suffix, const char *root, const char* path) {
+        _cleanup_strv_free_ char **copy = NULL;
+
+        assert(strv);
+        assert(suffix);
+
+        ssize_t path_length = conf_files_list_follow_path(path, NULL);
+        if (path_length < 0)
+                return -ENOMEM;
+
+        copy = new0(char *, path_length + 1);
+        if (!copy)
+                return -ENOMEM;
+        ssize_t error = conf_files_list_follow_path(path, copy);
+        if (error < 0)
+                return -ENOMEM;
+
+        assert (error == path_length);
+
+        return conf_files_list_strv_internal(strv, suffix, root, copy);
+}

src/shared/conf-files.h

@@ -23,3 +23,4 @@
 #include "macro.h"
 
 int conf_files_list_strv(char ***strv, const char *suffix, const char *root, const char* const* dirs);
+int conf_files_list_strv_path(char ***strv, const char *suffix, const char *root, const char* path);

src/udev/udevadm-hwdb.c

@@ -35,11 +35,17 @@
  * Uses a Patricia/radix trie to index all matches for efficient lookup.
  */
 
-static const char * const conf_file_dirs[] = {
-        UDEV_HWDB_DIR,
-        UDEV_LIBEXEC_DIR "/hwdb.d",
-        NULL
-};
+static char *list_conf_file_path (void) {
+        static const char *main_hwdb_dir = UDEV_HWDB_DIR;
+        static const char *libexec_dir = UDEV_LIBEXEC_DIR "/hwdb.d";
+        const char *path_variable = getenv ("UDEV_HWDB_PATH");
+        /* UDEV_HWDB_PATH comes last, so that it cannot override
+           system settings. */
+        /* System settings can be overriden by putting the files in
+           /etc. */
+        /* path_variable may be NULL, strjoin works either way. */
+        return strjoin(main_hwdb_dir, ":", libexec_dir, ":", path_variable, NULL);
+}
 
 /* in-memory trie objects */
 struct trie {
@@ -568,7 +574,12 @@ static void help(void) {
                "  --usr                generate in " UDEV_LIBEXEC_DIR " instead of /etc/udev\n"
                "  -t,--test=MODALIAS   query database and print result\n"
                "  -r,--root=PATH       alternative root path in the filesystem\n"
-               "  -h,--help\n\n");
+               "  -h,--help\n"
+               "\n"
+               "The HWDB is searched in "
+               UDEV_HWDB_DIR ", " UDEV_LIBEXEC_DIR "/hwdb.d, "
+               "and the UDEV_HWDB_PATH search path.\n"
+               "\n");
 }
 
 static int adm_hwdb(struct udev *udev, int argc, char *argv[]) {
@@ -677,7 +688,13 @@ static int adm_hwdb(struct udev *udev, int argc, char *argv[]) {
                 }
                 trie->nodes_count++;
 
-                err = conf_files_list_strv(&files, ".hwdb", root, conf_file_dirs);
+                _cleanup_free_ char *conf_file_path = list_conf_file_path ();
+                if (conf_file_path == NULL) {
+                        rc = EXIT_FAILURE;
+                        goto out;
+                }
+                err = conf_files_list_strv_path(&files, ".hwdb", root,
+                                                conf_file_path);
                 if (err < 0) {
                         log_error_errno(err, "failed to enumerate hwdb files: %m");
                         rc = EXIT_FAILURE;