[PATCH v2] platform/x86: asus-wmi: add keystone dongle support

[Dariusz Figzał]

The ASUS Keystone is a physical NFC-like dongle that slots into supported
ASUS laptops. The EC fires WMI notify code 0xB4 on insert/remove events.

Expose the current insert state via a sysfs attribute by querying WMI
device ID 0x00120091 (DSTS). This devid does not follow the standard DSTS
convention: PRESENCE_BIT (0x00010000) encodes the insert state rather than
feature presence, and STATUS_BIT is never set. Presence of a keystone slot
is detected by a successful DSTS call.

Signed-off-by: Dariusz Figzał <dariuszfigzal@xxxxxxxxx>
---

Changes in v2:
- Use .is_visible and platform_attributes[] instead of
  device_create_file/device_remove_file (Ilpo Järvinen)

 drivers/platform/x86/asus-wmi.c            | 65 ++++++++++++++++++++++
 include/linux/platform_data/x86/asus-wmi.h |  7 +++
 2 files changed, 72 insertions(+)

diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 80144c412b90..3c9ef826551d 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -70,6 +70,7 @@ module_param(fnlock_default, bool, 0444);
 #define NOTIFY_KBD_TTP			0xae
 #define NOTIFY_LID_FLIP			0xfa
 #define NOTIFY_LID_FLIP_ROG		0xbd
+#define NOTIFY_KEYSTONE			0xb4
 
 #define ASUS_WMI_FNLOCK_BIOS_DISABLED	BIT(0)
 
@@ -279,6 +280,8 @@ struct asus_wmi {
 	u32 tablet_switch_dev_id;
 	bool tablet_switch_inverted;
 
+	bool keystone_available;
+
 	enum fan_type fan_type;
 	enum fan_type gpu_fan_type;
 	enum fan_type mid_fan_type;
@@ -646,6 +649,55 @@ static bool asus_wmi_dev_is_present(struct asus_wmi *asus, u32 dev_id)
 	return status == 0 && (retval & ASUS_WMI_DSTS_PRESENCE_BIT);
 }
 
+/* Keystone *******************************************************************/
+
+static int keystone_check_present(struct asus_wmi *asus)
+{
+	u32 retval;
+	int err;
+
+	asus->keystone_available = false;
+
+	/*
+	 * Use a raw devstate call rather than asus_wmi_dev_is_present().
+	 * For this devid, PRESENCE_BIT encodes current insert state, not
+	 * feature presence, so asus_wmi_dev_is_present() would return false
+	 * whenever the dongle is absent at boot, even on machines that have
+	 * a keystone slot.
+	 * -ENODEV means the firmware doesn't know this devid at all.
+	 * retval is not examined here, only the return code matters.
+	 */
+	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
+	if (err == -ENODEV)
+		return 0;
+	if (err)
+		return err;
+
+	asus->keystone_available = true;
+	return 0;
+}
+
+static ssize_t keystone_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct asus_wmi *asus = dev_get_drvdata(dev);
+	u32 retval;
+	int err;
+
+	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
+	if (err)
+		return err;
+
+	return sysfs_emit(buf, "%d\n", !!(retval & ASUS_WMI_DSTS_PRESENCE_BIT));
+}
+
+static DEVICE_ATTR_RO(keystone);
+
+static void asus_wmi_keystone_notify(struct asus_wmi *asus)
+{
+	sysfs_notify(&asus->platform_device->dev.kobj, NULL, "keystone");
+}
+
 /* Input **********************************************************************/
 static void asus_wmi_tablet_sw_report(struct asus_wmi *asus, bool value)
 {
@@ -4575,6 +4627,12 @@ static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
 		return;
 	}
 
+	if (code == NOTIFY_KEYSTONE) {
+		if (asus->keystone_available)
+			asus_wmi_keystone_notify(asus);
+		return;
+	}
+
 	if (code == NOTIFY_KBD_FBM || code == NOTIFY_KBD_TTP) {
 		if (asus->fan_boost_mode_available)
 			fan_boost_mode_switch_next(asus);
@@ -4698,6 +4756,7 @@ static struct attribute *platform_attributes[] = {
 	&dev_attr_lid_resume.attr,
 	&dev_attr_als_enable.attr,
 	&dev_attr_fan_boost_mode.attr,
+	&dev_attr_keystone.attr,
 #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
 		&dev_attr_charge_mode.attr,
 		&dev_attr_egpu_enable.attr,
@@ -4741,6 +4800,8 @@ static umode_t asus_sysfs_is_visible(struct kobject *kobj,
 		devid = ASUS_WMI_DEVID_ALS_ENABLE;
 	else if (attr == &dev_attr_fan_boost_mode.attr)
 		ok = asus->fan_boost_mode_available;
+	else if (attr == &dev_attr_keystone.attr)
+		ok = asus->keystone_available;
 
 #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
 	if (attr == &dev_attr_charge_mode.attr)
@@ -5081,6 +5142,10 @@ static int asus_wmi_add(struct platform_device *pdev)
 	if (err)
 		goto fail_platform_profile_setup;
 
+	err = keystone_check_present(asus);
+	if (err)
+		dev_warn(&pdev->dev, "Failed to check Keystone presence: %d\n", err);
+
 	err = asus_wmi_sysfs_init(asus->platform_device);
 	if (err)
 		goto fail_sysfs;
diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
index 554f41b827e1..c29962d5baac 100644
--- a/include/linux/platform_data/x86/asus-wmi.h
+++ b/include/linux/platform_data/x86/asus-wmi.h
@@ -147,6 +147,13 @@
 #define ASUS_WMI_DEVID_GPU_MUX		0x00090016
 #define ASUS_WMI_DEVID_GPU_MUX_VIVO	0x00090026
 
+/* Keystone dongle insert/remove state.
+ * PRESENCE_BIT (0x00010000) encodes insert state:
+ * 0x00010000 = inserted, 0x00000000 = absent. STATUS_BIT is never set.
+ * 0xFFFFFFFE means no keystone slot on this machine.
+ */
+#define ASUS_WMI_DEVID_KEYSTONE		0x00120091
+
 /* TUF laptop RGB modes/colours */
 #define ASUS_WMI_DEVID_TUF_RGB_MODE	0x00100056
 #define ASUS_WMI_DEVID_TUF_RGB_MODE2	0x0010005A
-- 
2.54.0