libsensors: Treat devices without a known ancestor bus as virtual

Currently only hwmon devices that don't have a parent device are treated
as virtual. Let's extend the concept to hwmon devices, that don't have
a *recognized ancestor* device (hwmon devices that according to the kernel
don't reside on a bus that we recognize). This change is meant to address
cases where a hwmon device has a thermal class device for a parent, but
the thermal class device doesn't have a parent device.

These kind of hwmon devices started appearing in the 4.19 kernel
due to commit f6b6b52ef7a54160c0. It was not reported as a kernel
regression and fixed in the kernel, because according to
Documentation/admin-guide/sysfs-rules.rst, the change was OK to make
(it says "Position of devices along device chain can change").

Fixes #139

Signed-off-by: Ondřej Lysoněk <olysonek@redhat.com>

1 files changed, 12 insertions, 4 deletions

diff --git a/lib/sysfs.c b/lib/sysfs.c
index 1691b9f5..e63688b7 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -759,6 +759,7 @@ static int sensors_read_one_sysfs_chip(const char *dev_path,
 				       const char *hwmon_path)
 {
 	int ret = 1;
+	int virtual = 0;
 	sensors_chip_features entry;
 
 	/* ignore any device without name attribute */
@@ -770,15 +771,22 @@ static int sensors_read_one_sysfs_chip(const char *dev_path,
 		sensors_fatal_error(__func__, "Out of memory");
 
 	if (dev_path == NULL) {
+		virtual = 1;
+	} else {
+		ret = find_bus_type(dev_path, dev_name, &entry);
+		if (ret == 0) {
+			virtual = 1;
+			ret = 1;
+		} else if (ret < 0) {
+			goto exit_free;
+		}
+	}
+	if (virtual) {
 		/* Virtual device */
 		entry.chip.bus.type = SENSORS_BUS_TYPE_VIRTUAL;
 		entry.chip.bus.nr = 0;
 		/* For now we assume that virtual devices are unique */
 		entry.chip.addr = 0;
-	} else {
-		ret = find_bus_type(dev_path, dev_name, &entry);
-		if (ret <= 0)
-			goto exit_free;
 	}
 
 	if (sensors_read_dynamic_chip(&entry, hwmon_path) < 0) {