ucm: implement ${sys:sysfs/path} substitution

Example:

Condition {
	Type String
	String1 "${sys:class/dmi/id/board_vendor}"
	String2 "LENOVO"
}

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/src/ucm/ucm_subs.c b/src/ucm/ucm_subs.c
index f20c8e22207627970211d5a1c24822e3def947b2..22dc24e9a48f5c8c398727cf6106518fe560cfa8 100644 (file)
--- a/src/ucm/ucm_subs.c
+++ b/src/ucm/ucm_subs.c
@@ -25,6 +25,8 @@
  */
 
 #include "ucm_local.h"
+#include <sys/stat.h>
+#include <limits.h>
 
 static char *rval_conf_name(snd_use_case_mgr_t *uc_mgr)
 {
@@ -83,6 +85,56 @@ static char *rval_env(snd_use_case_mgr_t *uc_mgr ATTRIBUTE_UNUSED, const char *i
        return NULL;
 }
 
+static char *rval_sysfs(snd_use_case_mgr_t *uc_mgr ATTRIBUTE_UNUSED, const char *id)
+{
+       char path[PATH_MAX], link[PATH_MAX + 1];
+       struct stat sb;
+       ssize_t len;
+       char *e;
+       int fd;
+
+       e = getenv("SYSFS_PATH");
+       if (e == NULL)
+               e = "/sys";
+       if (id[0] == '/')
+               id++;
+       snprintf(path, sizeof(path), "%s/%s", e, id);
+       if (lstat(path, &sb) != 0)
+               return NULL;
+       if (S_ISLNK(sb.st_mode)) {
+               len = readlink(path, link, sizeof(link) - 1);
+               if (len <= 0) {
+                       uc_error("sysfs: cannot read link '%s' (%d)", path, errno);
+                       return NULL;
+               }
+               link[len] = '\0';
+               e = strrchr(link, '/');
+               if (e)
+                       return strdup(e + 1);
+               return NULL;
+       }
+       if (S_ISDIR(sb.st_mode))
+               return NULL;
+       if ((sb.st_mode & S_IRUSR) == 0)
+               return NULL;
+
+       fd = open(path, O_RDONLY);
+       if (fd < 0) {
+               uc_error("sysfs open failed for '%s' (%d)", path, errno);
+               return NULL;
+       }
+       len = read(fd, path, sizeof(path)-1);
+       close(fd);
+       if (len < 0) {
+               uc_error("sysfs unable to read value '%s' (%d)", path, errno);
+               return NULL;
+       }
+       while (len > 0 && path[len-1] == '\n')
+               len--;
+       path[len] = '\0';
+       return strdup(path);
+}
+
 #define MATCH_VARIABLE(name, id, fcn)                                  \
        if (strncmp((name), (id), sizeof(id) - 1) == 0) {               \
                rval = fcn(uc_mgr);                                     \
@@ -133,6 +185,7 @@ int uc_mgr_get_substituted_value(snd_use_case_mgr_t *uc_mgr,
                        MATCH_VARIABLE(value, "${CardLongName}", rval_card_longname);
                        MATCH_VARIABLE(value, "${CardComponents}", rval_card_components);
                        MATCH_VARIABLE2(value, "${env:", rval_env);
+                       MATCH_VARIABLE2(value, "${sys:", rval_sysfs);
                        err = -EINVAL;
                        tmp = strchr(value, '}');
                        if (tmp) {