Re: [PATCH v5 2/4] Fix SW_TABLET_MODE detection method

[Stefan Sichler <stsichler@web.de>]

Hi,
this patch (which is now committed to the kernel as commit
520ee4ea1cc60251a6e3c911cf0336278aa52634 since v5.18-rc1) unfortunately
introduced a regression on my HP EliteBook 2760p Convertible:

Tablet mode is no longer detected.

It worked flawlessly before (when enable_tablet_mode_sw module param was
set to 1).

Debugging showed that on this device, two problems prevent the table
mode detection from working:

   - Chassis Type is reported as 0x10 (= Lunch Box)

   - the query of HPWMI_SYSTEM_DEVICE_MODE does not report tablet state
at all

Note that the chassis type of this device (switch to tablet mode by
screen *rotation*) actually differs from the newer HP models (switch to
tablet mode by screen *flipping*).


I suggest fixing this by re-adding the removed module parameter
"enable_tablet_mode_sw", but change its behavior to work in the
following way:

   - when left at default -1 (auto): no change to current (new)
implementation

   - when set to 0: unconditionally disable table mode reporting at all

   - when set to 1: ignore Chassis type and use old-skool
hp_wmi_hw_state(HPWMI_TABLET_MASK) query method to determine tablet mode
in addition to new hp_wmi_perform_query(HPWMI_SYSTEM_DEVICE_MODE...) method


I prepared a patch based on commit
520ee4ea1cc60251a6e3c911cf0336278aa52634, and tested it successfully on
my device.
See below.

Regards,
Stefan

--- hp-wmi.c.orig	2024-03-10 21:38:09.000000000 +0100
+++ hp-wmi.c	2024-08-08 09:23:29.509113900 +0200
@@ -35,6 +35,10 @@
  MODULE_ALIAS("wmi:95F24279-4D7B-4334-9387-ACCDC67EF61C");
  MODULE_ALIAS("wmi:5FB7F034-2C63-45e9-BE91-3D44E2C707E4");

+static int enable_tablet_mode_sw = -1;
+module_param(enable_tablet_mode_sw, int, 0444);
+MODULE_PARM_DESC(enable_tablet_mode_sw, "Enable SW_TABLET_MODE
reporting (-1=auto, 0=no, 1=yes)");
+
  #define HPWMI_EVENT_GUID "95F24279-4D7B-4334-9387-ACCDC67EF61C"
  #define HPWMI_BIOS_GUID "5FB7F034-2C63-45e9-BE91-3D44E2C707E4"
  #define HP_OMEN_EC_THERMAL_PROFILE_OFFSET 0x95
@@ -428,6 +432,9 @@
  	bool tablet_found;
  	int ret;

+	if (!enable_tablet_mode_sw)
+		return -ENODEV;
+
  	chassis_type = dmi_get_system_info(DMI_CHASSIS_TYPE);
  	if (!chassis_type)
  		return -ENODEV;
@@ -435,16 +442,24 @@
  	tablet_found = match_string(tablet_chassis_types,
  				    ARRAY_SIZE(tablet_chassis_types),
  				    chassis_type) >= 0;
-	if (!tablet_found)
+	if (!tablet_found && enable_tablet_mode_sw < 0 /*auto*/)
  		return -ENODEV;

  	ret = hp_wmi_perform_query(HPWMI_SYSTEM_DEVICE_MODE, HPWMI_READ,
  				   system_device_mode, zero_if_sup(system_device_mode),
  				   sizeof(system_device_mode));
-	if (ret < 0)
-		return ret;
+	if (ret >= 0)
+		ret = (system_device_mode[0] == DEVICE_MODE_TABLET);
+
+	/* workaround for older convertibles */
+	if (ret <= 0 && enable_tablet_mode_sw > 0)
+	{
+		ret = hp_wmi_read_int(HPWMI_HARDWARE_QUERY);
+		if (!(ret < 0))
+			ret = !!(ret & HPWMI_TABLET_MASK);
+	}

-	return system_device_mode[0] == DEVICE_MODE_TABLET;
+	return ret;
  }

  static int omen_thermal_profile_set(int mode)