platform/x86: ideapad-laptop: always propagate error codes from device attributes' show() callback

Consumers can differentiate an error from a successful read much more
easily if the read() call fails with an appropriate errno instead of
returning a magic string like "-1". This introduces an ABI change, but
not many users are expected to be relying on the previous behavior,
and this change makes this module conforming to the standard behavior
that sysfs attribute show/store callbacks return an appropriate
errno in case of failure. Thus the ABI breakage is deemed justified.
Signed-off-by: Barnabás Pőcze <pobrn@protonmail.com>
Link: https://lore.kernel.org/r/20210203215403.290792-15-pobrn@protonmail.comReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/ideapad-laptop.c

@@ -380,9 +380,11 @@ static ssize_t show_ideapad_cam(struct device *dev,
 {
 	unsigned long result;
 	struct ideapad_private *priv = dev_get_drvdata(dev);
+	int err;
 
-	if (read_ec_data(priv->adev->handle, VPCCMD_R_CAMERA, &result))
-		return sysfs_emit(buf, "-1\n");
+	err = read_ec_data(priv->adev->handle, VPCCMD_R_CAMERA, &result);
+	if (err)
+		return err;
 	return sysfs_emit(buf, "%lu\n", result);
 }
 
@@ -411,9 +413,11 @@ static ssize_t show_ideapad_fan(struct device *dev,
 {
 	unsigned long result;
 	struct ideapad_private *priv = dev_get_drvdata(dev);
+	int err;
 
-	if (read_ec_data(priv->adev->handle, VPCCMD_R_FAN, &result))
-		return sysfs_emit(buf, "-1\n");
+	err = read_ec_data(priv->adev->handle, VPCCMD_R_FAN, &result);
+	if (err)
+		return err;
 	return sysfs_emit(buf, "%lu\n", result);
 }
 
@@ -444,9 +448,11 @@ static ssize_t touchpad_show(struct device *dev,
 {
 	struct ideapad_private *priv = dev_get_drvdata(dev);
 	unsigned long result;
+	int err;
 
-	if (read_ec_data(priv->adev->handle, VPCCMD_R_TOUCHPAD, &result))
-		return sysfs_emit(buf, "-1\n");
+	err = read_ec_data(priv->adev->handle, VPCCMD_R_TOUCHPAD, &result);
+	if (err)
+		return err;
 	return sysfs_emit(buf, "%lu\n", result);
 }
 
@@ -477,9 +483,11 @@ static ssize_t conservation_mode_show(struct device *dev,
 {
 	struct ideapad_private *priv = dev_get_drvdata(dev);
 	unsigned long result;
+	int err;
 
-	if (method_gbmd(priv->adev->handle, &result))
-		return sysfs_emit(buf, "-1\n");
+	err = method_gbmd(priv->adev->handle, &result);
+	if (err)
+		return err;
 	return sysfs_emit(buf, "%u\n", test_bit(BM_CONSERVATION_BIT, &result));
 }
 
@@ -515,7 +523,7 @@ static ssize_t fn_lock_show(struct device *dev,
 	int fail = read_method_int(priv->adev->handle, "HALS", &hals);
 
 	if (fail)
-		return sysfs_emit(buf, "-1\n");
+		return fail;
 
 	result = hals;
 	return sysfs_emit(buf, "%u\n", test_bit(HA_FNLOCK_BIT, &result));