platform/chrome: cros_ec_sysfs: Expose AP_MODE_ENTRY feature state

This adds sysfs attribute /sys/class/chromeos/cros_ec/ap_mode_entry
to expose the status of the AP_MODE_ENTRY feature. This attribute
indicate whether the EC requires direction from the Application
Processor (AP) before entering Type-C alternate modes or USB4 mode.
This allows user-space applications to easily determine if the AP needs
to be involved in mode entry.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Link: https://lore.kernel.org/r/20250203125947.2701106-3-akuchynski@chromium.org
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

Author: Andrei Kuchynski

Documentation/ABI/testing/sysfs-class-chromeos

@@ -44,3 +44,10 @@ Description:
 		- "SAFE": DP is in safe mode
 		- "TBT": TBT enabled
 		- "USB4": USB4 enabled
+
+What:		/sys/class/chromeos/cros_ec/ap_mode_entry
+Date:		February 2025
+Description:
+		Show if the AP mode entry EC feature is supported.
+		It indicates whether the EC waits for direction from the AP
+		to enter Type-C altmodes or USB4 mode.

drivers/platform/chrome/cros_ec_sysfs.c

@@ -345,20 +345,32 @@ static ssize_t usbpdmuxinfo_show(struct device *dev,
 	return count ? : -EIO;
 }
 
+static ssize_t ap_mode_entry_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct cros_ec_dev *ec = to_cros_ec_dev(dev);
+	const bool ap_driven_altmode = cros_ec_check_features(
+		ec, EC_FEATURE_TYPEC_REQUIRE_AP_MODE_ENTRY);
+
+	return sysfs_emit(buf, "%s\n", ap_driven_altmode ? "yes" : "no");
+}
+
 /* Module initialization */
 
 static DEVICE_ATTR_RW(reboot);
 static DEVICE_ATTR_RO(version);
 static DEVICE_ATTR_RO(flashinfo);
 static DEVICE_ATTR_RW(kb_wake_angle);
 static DEVICE_ATTR_RO(usbpdmuxinfo);
+static DEVICE_ATTR_RO(ap_mode_entry);
 
 static struct attribute *__ec_attrs[] = {
 	&dev_attr_kb_wake_angle.attr,
 	&dev_attr_reboot.attr,
 	&dev_attr_version.attr,
 	&dev_attr_flashinfo.attr,
 	&dev_attr_usbpdmuxinfo.attr,
+	&dev_attr_ap_mode_entry.attr,
 	NULL,
 };
 
@@ -371,7 +383,8 @@ static umode_t cros_ec_ctrl_visible(struct kobject *kobj,
 	if (a == &dev_attr_kb_wake_angle.attr && !ec->has_kb_wake_angle)
 		return 0;
 
-	if (a == &dev_attr_usbpdmuxinfo.attr) {
+	if (a == &dev_attr_usbpdmuxinfo.attr ||
+		a == &dev_attr_ap_mode_entry.attr) {
 		struct cros_ec_platform *ec_platform = dev_get_platdata(ec->dev);
 
 		if (strcmp(ec_platform->ec_name, CROS_EC_DEV_NAME))