lib/sysfs: add subsystem and hotplug detection

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/include/sysfs.h b/include/sysfs.h
index 3ff20cb2703cbe81ec8ef544ab0d88168b89375d..1de624aadcb14d697ee38951cc56ef19ae59615a 100644 (file)
--- a/include/sysfs.h
+++ b/include/sysfs.h
@@ -70,6 +70,10 @@ extern int sysfs_count_partitions(struct sysfs_cxt *cxt, const char *devname);
 extern dev_t sysfs_partno_to_devno(struct sysfs_cxt *cxt, int partno);
 extern char *sysfs_get_slave(struct sysfs_cxt *cxt);
 
+extern char *sysfs_get_devchain(struct sysfs_cxt *cxt, char *buf, size_t bufsz);
+extern int sysfs_next_subsystem(struct sysfs_cxt *cxt, char *devchain, char **subsys);
+extern int sysfs_is_hotpluggable(struct sysfs_cxt *cxt);
+
 extern int sysfs_is_partition_dirent(DIR *dir, struct dirent *d,
                        const char *parent_name);
 

diff --git a/lib/sysfs.c b/lib/sysfs.c
index e2baf7fcd3e98ad0cdf42dd625b2abf03b603e2f..63a90dcbca44c5bcf7761e4321474a6600f2bc30 100644 (file)
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -547,6 +547,146 @@ char *sysfs_get_devname(struct sysfs_cxt *cxt, char *buf, size_t bufsiz)
        return buf;
 }
 
+#define SUBSYSTEM_LINKNAME     "/subsystem"
+
+/*
+ * For example:
+ *
+ * chain: /sys/dev/block/../../devices/pci0000:00/0000:00:1a.0/usb1/1-1/1-1.2/ \
+ *                           1-1.2:1.0/host65/target65:0:0/65:0:0:0/block/sdb
+ *
+ * The function check if <chain>/subsystem symlink exists, if yes then returns
+ * basename of the readlink result, and remove the last subdirectory from the
+ * <chain> path.
+ */
+static char *get_subsystem(char *chain, char *buf, size_t bufsz)
+{
+       size_t len;
+       char *p;
+
+       if (!chain || !*chain)
+               return NULL;
+
+       len = strlen(chain);
+       if (len + sizeof(SUBSYSTEM_LINKNAME) > PATH_MAX)
+               return NULL;
+
+       do {
+               ssize_t sz;
+
+               /* append "/subsystem" to the path */
+               memcpy(chain + len, SUBSYSTEM_LINKNAME, sizeof(SUBSYSTEM_LINKNAME));
+
+               /* try if subsystem symlink exists */
+               sz = readlink(chain, buf, bufsz - 1);
+
+               /* remove last subsystem from chain */
+               chain[len] = '\0';
+               p = strrchr(chain, '/');
+               if (p) {
+                       *p = '\0';
+                       len = p - chain;
+               }
+
+               if (sz > 0) {
+                       /* we found symlink to subsystem, return basename */
+                       buf[sz] = '\0';
+                       return basename(buf);
+               }
+
+       } while (p);
+
+       return NULL;
+}
+
+/*
+ * Returns complete path to the device, the patch contains all all sybsystems
+ * used for the device.
+ */
+char *sysfs_get_devchain(struct sysfs_cxt *cxt, char *buf, size_t bufsz)
+{
+       /* read /sys/dev/block/<maj>:<min> symlink */
+       size_t sz = sysfs_readlink(cxt, NULL, buf, bufsz);
+       if (sz <= 0 || sz + sizeof(_PATH_SYS_DEVBLOCK "/") > bufsz)
+               return NULL;
+
+       buf[sz++] = '\0';
+
+       /* create absolute patch from the link */
+       memmove(buf + sizeof(_PATH_SYS_DEVBLOCK "/") - 1, buf, sz);
+       memcpy(buf, _PATH_SYS_DEVBLOCK "/", sizeof(_PATH_SYS_DEVBLOCK "/") - 1);
+
+       return buf;
+}
+
+/*
+ * The @subsys returns the next subsystem in the chain. Function modifies
+ * @devchain string.
+ *
+ * Returns: 0 in success, <0 on error, 1 on end of chain
+ */
+int sysfs_next_subsystem(struct sysfs_cxt *cxt __attribute__((unused)),
+                        char *devchain, char **subsys)
+{
+       char subbuf[PATH_MAX];
+       char *sub;
+
+       if (!subsys || !devchain)
+               return -EINVAL;
+
+       while ((sub = get_subsystem(devchain, subbuf, sizeof(subbuf)))) {
+               *subsys = strdup(sub);
+               if (!*subsys)
+                       return -ENOMEM;
+               return 0;
+       }
+
+       return 1;
+}
+
+
+static int is_hotpluggable_subsystem(const char *name)
+{
+       static const char * const hotplug_subsystems[] = {
+               "usb",
+               "ieee1394",
+               "pcmcia",
+               "mmc",
+               "ccw"
+       };
+       size_t i;
+
+       for (i = 0; i < ARRAY_SIZE(hotplug_subsystems); i++)
+               if (strcmp(name, hotplug_subsystems[i]) == 0)
+                       return 1;
+
+       return 0;
+}
+
+int sysfs_is_hotpluggable(struct sysfs_cxt *cxt)
+{
+       char buf[PATH_MAX], *chain, *sub;
+       int rc = 0;
+
+
+       /* check /sys/dev/block/<maj>:<min>/removable attribute */
+       if (sysfs_read_int(cxt, "removable", &rc) == 0 && rc == 1)
+               return 1;
+
+       chain = sysfs_get_devchain(cxt, buf, sizeof(buf));
+
+       while (chain && sysfs_next_subsystem(cxt, chain, &sub) == 0) {
+               rc = is_hotpluggable_subsystem(sub);
+               if (rc) {
+                       free(sub);
+                       break;
+               }
+               free(sub);
+       }
+
+       return rc;
+}
+
 static int get_dm_wholedisk(struct sysfs_cxt *cxt, char *diskname,
                 size_t len, dev_t *diskdevno)
 {
@@ -711,6 +851,7 @@ int sysfs_devno_is_wholedisk(dev_t devno)
        return devno == disk;
 }
 
+
 int sysfs_scsi_get_hctl(struct sysfs_cxt *cxt, int *h, int *c, int *t, int *l)
 {
        char buf[PATH_MAX], *hctl;
@@ -858,7 +999,7 @@ int main(int argc, char *argv[])
        struct sysfs_cxt cxt = UL_SYSFSCXT_EMPTY;
        char *devname;
        dev_t devno;
-       char path[PATH_MAX];
+       char path[PATH_MAX], *sub, *chain;
        int i, is_part;
        uint64_t u64;
        ssize_t len;
@@ -911,6 +1052,16 @@ int main(int argc, char *argv[])
                printf("SECTOR: %d\n", i);
 
        printf("DEVNAME: %s\n", sysfs_get_devname(&cxt, path, sizeof(path)));
+       printf("HOTPLUG: %s\n", sysfs_is_hotpluggable(&cxt) ? "yes" : "no");
+
+       chain = sysfs_get_devchain(&cxt, path, sizeof(path));
+       printf("SUBSUSTEMS:\n");
+
+       while (chain && sysfs_next_subsystem(&cxt, chain, &sub) == 0) {
+               printf("\t%s\n", sub);
+               free(sub);
+       }
+
 
        sysfs_deinit(&cxt);
        return EXIT_SUCCESS;