[PATCH v2] driver core: bus: Return -EIO instead of 0 when show/store invalid bus attribute

[Zijun Hu <zijun_hu@icloud.com>]

From: Zijun Hu <quic_zijuhu@quicinc.com>

Return -EIO instead of 0 for below erroneous bus attribute operations:
 - read a bus attribute without show().
 - write a bus attribute without store().

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
---
Changes in v2:
- Correct commit messages and add inline comments
- The following commit have similar change
  Commit: 4a0c20bf8c0f ("[PATCH] sysfs: (driver/base) if show/store is missing return -EIO")
- Link to v1: https://lore.kernel.org/r/20240723-bus_fix-v1-1-175f926805dc@quicinc.com
---
 drivers/base/bus.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index ffea0728b8b2..e5073fa82b95 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -152,7 +152,8 @@ static ssize_t bus_attr_show(struct kobject *kobj, struct attribute *attr,
 {
 	struct bus_attribute *bus_attr = to_bus_attr(attr);
 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
-	ssize_t ret = 0;
+	/* return -EIO for reading a bus attribute without show() */
+	ssize_t ret = -EIO;
 
 	if (bus_attr->show)
 		ret = bus_attr->show(subsys_priv->bus, buf);
@@ -164,7 +165,8 @@ static ssize_t bus_attr_store(struct kobject *kobj, struct attribute *attr,
 {
 	struct bus_attribute *bus_attr = to_bus_attr(attr);
 	struct subsys_private *subsys_priv = to_subsys_private(kobj);
-	ssize_t ret = 0;
+	/* return -EIO for writing a bus attribute without store() */
+	ssize_t ret = -EIO;
 
 	if (bus_attr->store)
 		ret = bus_attr->store(subsys_priv->bus, buf, count);

---
base-commit: b57d5ffc3ab507d0e19fc8b90b19c76af43fb790
change-id: 20240723-bus_fix-1940d8e79e92

Best regards,
-- 
Zijun Hu <quic_zijuhu@quicinc.com>