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Subject[PATCH v4 05/13] platform/x86: asus-wmi: Improve DSTS WMI method ID detection
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The DSTS method detection mistakenly selects DCTS instead of DSTS if
nothing is returned when the method ID is not defined in WMNB. As a result,
the control of keyboard backlight is not functional for TUF Gaming series
laptops. Implement detection based on _UID of the WMI device instead.

There is evidence that DCTS is handled by ACPI WMI devices that have _UID
ASUSWMI, whereas none of the devices without ASUSWMI respond to DCTS and
DSTS is used instead [1].

DSDT examples:

FX505GM (_UID ATK):
Method (WMNB, 3, Serialized)
{ ...
If ((Local0 == 0x53545344))
{
...
Return (Zero)
}
...
// No return
}

K54C (_UID ATK):
Method (WMNB, 3, Serialized)
{ ...
If ((Local0 == 0x53545344))
{
...
Return (0x02)
}
...
Return (0xFFFFFFFE)
}

[1] Link: https://lkml.org/lkml/2019/4/11/322

Signed-off-by: Yurii Pavlovskyi <yurii.pavlovskyi@gmail.com>
Suggested-by: Daniel Drake <drake@endlessm.com>

---
Depends on the previous patch in the series that adds method to
wmi module.
---
drivers/hid/hid-asus.c | 2 +-
drivers/platform/x86/asus-wmi.c | 23 +++++++++++++++++++---
include/linux/platform_data/x86/asus-wmi.h | 4 ++--
3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/hid-asus.c b/drivers/hid/hid-asus.c
index 336aeaed1159..1d01fe23ca0c 100644
--- a/drivers/hid/hid-asus.c
+++ b/drivers/hid/hid-asus.c
@@ -396,7 +396,7 @@ static bool asus_kbd_wmi_led_control_present(struct hid_device *hdev)
if (!IS_ENABLED(CONFIG_ASUS_WMI))
return false;

- ret = asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS2,
+ ret = asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS,
ASUS_WMI_DEVID_KBD_BACKLIGHT, 0, &value);
hid_dbg(hdev, "WMI backlight check: rc %d value %x", ret, value);
if (ret)
diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
index 6b35c1f00a3e..5bdb4ffdbee3 100644
--- a/drivers/platform/x86/asus-wmi.c
+++ b/drivers/platform/x86/asus-wmi.c
@@ -83,6 +83,8 @@ MODULE_LICENSE("GPL");
#define USB_INTEL_XUSB2PR 0xD0
#define PCI_DEVICE_ID_INTEL_LYNXPOINT_LP_XHCI 0x9c31

+#define ASUS_ACPI_UID_ASUSWMI "ASUSWMI"
+
static const char * const ashs_ids[] = { "ATK4001", "ATK4002", NULL };

static bool ashs_present(void)
@@ -1874,6 +1876,8 @@ static int asus_wmi_sysfs_init(struct platform_device *device)
*/
static int asus_wmi_platform_init(struct asus_wmi *asus)
{
+ struct device *dev = &asus->platform_device->dev;
+ char *wmi_uid;
int rv;

/* INIT enable hotkeys on some models */
@@ -1903,11 +1907,24 @@ static int asus_wmi_platform_init(struct asus_wmi *asus)
* Note, on most Eeepc, there is no way to check if a method exist
* or note, while on notebooks, they returns 0xFFFFFFFE on failure,
* but once again, SPEC may probably be used for that kind of things.
+ *
+ * Additionally at least TUF Gaming series laptops return nothing for
+ * unknown methods, so the detection in this way is not possible.
+ *
+ * There is strong indication that only ACPI WMI devices that have _UID
+ * equal to "ASUSWMI" use DCTS whereas those with "ATK" use DSTS.
*/
- if (!asus_wmi_evaluate_method(ASUS_WMI_METHODID_DSTS, 0, 0, NULL))
+ wmi_uid = wmi_get_acpi_device_uid(ASUS_WMI_MGMT_GUID);
+ if (!wmi_uid)
+ return -ENODEV;
+
+ if (!strcmp(wmi_uid, ASUS_ACPI_UID_ASUSWMI)) {
+ dev_info(dev, "Detected ASUSWMI, use DCTS\n");
+ asus->dsts_id = ASUS_WMI_METHODID_DCTS;
+ } else {
+ dev_info(dev, "Detected %s, not ASUSWMI, use DSTS\n", wmi_uid);
asus->dsts_id = ASUS_WMI_METHODID_DSTS;
- else
- asus->dsts_id = ASUS_WMI_METHODID_DSTS2;
+ }

/* CWAP allow to define the behavior of the Fn+F2 key,
* this method doesn't seems to be present on Eee PCs */
diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
index bfba245636a7..0668f76df921 100644
--- a/include/linux/platform_data/x86/asus-wmi.h
+++ b/include/linux/platform_data/x86/asus-wmi.h
@@ -18,8 +18,8 @@
#define ASUS_WMI_METHODID_GDSP 0x50534447 /* Get DiSPlay output */
#define ASUS_WMI_METHODID_DEVP 0x50564544 /* DEVice Policy */
#define ASUS_WMI_METHODID_OSVR 0x5256534F /* OS VeRsion */
-#define ASUS_WMI_METHODID_DSTS 0x53544344 /* Device STatuS */
-#define ASUS_WMI_METHODID_DSTS2 0x53545344 /* Device STatuS #2*/
+#define ASUS_WMI_METHODID_DCTS 0x53544344 /* Device status (DCTS) */
+#define ASUS_WMI_METHODID_DSTS 0x53545344 /* Device status (DSTS) */
#define ASUS_WMI_METHODID_BSTS 0x53545342 /* Bios STatuS ? */
#define ASUS_WMI_METHODID_DEVS 0x53564544 /* DEVice Set */
#define ASUS_WMI_METHODID_CFVS 0x53564643 /* CPU Frequency Volt Set */
--
2.17.1
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