Re: [PATCH] platform/x86: thinkpad-acpi: Add X1 Fold keyboard attachment detection

[Pit Henrich]

Heya,

>  - We usually do the DMI_MATCH on the BOARD_NAME for quirks. I was checking psref.lenovo.com and there seem to be two distinct models for this platform, which is a bit confusing. I don't have a way to confirm that your changes will work for the other model so wondering if it's safer to do the quirks for 21ES/21ET or 20RL/20RK depending on what you have in hand? (I might be overthinking this too)

I based this on the code in drivers/platform/x86/intel/hid.c which
also does a DMI_MATCH against DMI_PRODUCT_FAMILY.
Just for the records: I have an ES21 model, and the code in
drivers/platform/x86/intel/hid.c works for me too (correctly enables
the 5-button array).

> If I get details back on the EC spec and confirmation it's correct I'll let you know :)

Awesome :)

Greetings
Pit

On Sat, 14 Mar 2026 at 19:24, Mark Pearson <mpearson-lenovo@xxxxxxxxx> wrote:
>
> Hi Pit,
>
> On Sat, Mar 14, 2026, at 10:22 AM, Pit Henrich wrote:
> > ThinkPad X1 Fold 16 Gen 1 firmware reports whether the keyboard is magnetically
> > attached (on the screen) via EC register 0xc1 bit 7, but thinkpad-acpi does
> > not expose this to userspace.
> >
> > Add a read-only keyboard_attached_on_screen sysfs attribute, gated by
> > a DMI match. The state is read directly from the EC.
> >
> > Cache the state and emit a sysfs notification on
> > TP_HKEY_EV_TABLET_CHANGED (0x60c0) when it changes. Initialize the cache during
> > hotkey setup and refresh it before the resume notification to keep the state
> > consistent across suspend and resume.
> >
> > Signed-off-by: Pit Henrich <pithenrich2d@xxxxxxxxx>
> > ---
> >  drivers/platform/x86/lenovo/thinkpad_acpi.c | 92 ++++++++++++++++++++-
> >  1 file changed, 90 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c
> > b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> > index 8982d92dfd97..5b255062ff51 100644
> > --- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
> > +++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
> > @@ -218,8 +218,9 @@ enum tpacpi_hkey_event_t {
> >       TP_HKEY_EV_LID_OPEN             = 0x5002, /* laptop lid opened */
> >       TP_HKEY_EV_TABLET_TABLET        = 0x5009, /* tablet swivel up */
> >       TP_HKEY_EV_TABLET_NOTEBOOK      = 0x500a, /* tablet swivel down */
> > -     TP_HKEY_EV_TABLET_CHANGED       = 0x60c0, /* X1 Yoga (2016):
> > -                                                * enter/leave tablet mode
> > +     TP_HKEY_EV_TABLET_CHANGED       = 0x60c0, /* posture change event:
> > +                                                * X1 Yoga (2016): enter/leave tablet mode
> > +                                                * X1 Fold 16 Gen 1: keyboard attachment state changed
> >                                                  */
> >       TP_HKEY_EV_PEN_INSERTED         = 0x500b, /* tablet pen inserted */
> >       TP_HKEY_EV_PEN_REMOVED          = 0x500c, /* tablet pen removed */
> > @@ -375,6 +376,7 @@ static struct {
> >       u32 has_adaptive_kbd:1;
> >       u32 kbd_lang:1;
> >       u32 trackpoint_doubletap:1;
> > +     u32 has_keyboard_attached_on_screen:1;
> >       struct quirk_entry *quirks;
> >  } tp_features;
> >
> > @@ -2928,6 +2930,70 @@ static void hotkey_tablet_mode_notify_change(void)
> >                            "hotkey_tablet_mode");
> >  }
> >
> > +/*
> > + * On the ThinkPad X1 Fold 16 Gen 1, EC register 0xc1 reports the
> > keyboard
> > + * attachment state in bit 7.
> > + */
> > +#define TPACPI_X1_FOLD_KBD_EC_STATUS 0xc1
> > +#define TPACPI_X1_FOLD_KBD_ATTACHED  BIT(7)
> > +
> > +static bool keyboard_attached_on_screen;
> > +static bool keyboard_attached_on_screen_initialized;
> > +
> > +static int x1_fold_keyboard_attached_on_screen_get(bool *attached)
> > +{
> > +     u8 status;
> > +
> > +     if (!tp_features.has_keyboard_attached_on_screen)
> > +             return -ENODEV;
> > +
> > +     if (!acpi_ec_read(TPACPI_X1_FOLD_KBD_EC_STATUS, &status))
> > +             return -EIO;
> > +
> > +     *attached = status & TPACPI_X1_FOLD_KBD_ATTACHED;
> > +     return 0;
> > +}
> > +
> > +static ssize_t keyboard_attached_on_screen_show(struct device *dev,
> > +                                             struct device_attribute *attr,
> > +                                             char *buf)
> > +{
> > +     bool attached;
> > +     int res;
> > +
> > +     res = x1_fold_keyboard_attached_on_screen_get(&attached);
> > +     if (res)
> > +             return res;
> > +
> > +     return sysfs_emit(buf, "%d\n", attached);
> > +}
> > +
> > +static DEVICE_ATTR_RO(keyboard_attached_on_screen);
> > +
> > +static void keyboard_attached_on_screen_notify_change(void)
> > +{
> > +     if (tp_features.has_keyboard_attached_on_screen)
> > +             sysfs_notify(&tpacpi_pdev->dev.kobj, NULL,
> > +                          "keyboard_attached_on_screen");
> > +}
> > +
> > +static bool keyboard_attached_on_screen_update(void)
> > +{
> > +     bool attached;
> > +
> > +     if (x1_fold_keyboard_attached_on_screen_get(&attached))
> > +             return false;
> > +
> > +     if (keyboard_attached_on_screen_initialized &&
> > +         keyboard_attached_on_screen == attached)
> > +             return false;
> > +
> > +     keyboard_attached_on_screen = attached;
> > +     keyboard_attached_on_screen_initialized = true;
> > +
> > +     return true;
> > +}
> > +
> >  /* sysfs wakeup reason (pollable)
> > -------------------------------------- */
> >  static ssize_t hotkey_wakeup_reason_show(struct device *dev,
> >                          struct device_attribute *attr,
> > @@ -3032,6 +3098,7 @@ static struct attribute *hotkey_attributes[] = {
> >       &dev_attr_hotkey_adaptive_all_mask.attr,
> >       &dev_attr_hotkey_recommended_mask.attr,
> >       &dev_attr_hotkey_tablet_mode.attr,
> > +     &dev_attr_keyboard_attached_on_screen.attr,
> >       &dev_attr_hotkey_radio_sw.attr,
> >  #ifdef CONFIG_THINKPAD_ACPI_HOTKEY_POLL
> >       &dev_attr_hotkey_source_mask.attr,
> > @@ -3046,6 +3113,9 @@ static umode_t hotkey_attr_is_visible(struct
> > kobject *kobj,
> >       if (attr == &dev_attr_hotkey_tablet_mode.attr) {
> >               if (!tp_features.hotkey_tablet)
> >                       return 0;
> > +     } else if (attr == &dev_attr_keyboard_attached_on_screen.attr) {
> > +             if (!tp_features.has_keyboard_attached_on_screen)
> > +                     return 0;
> >       } else if (attr == &dev_attr_hotkey_radio_sw.attr) {
> >               if (!tp_features.hotkey_wlsw)
> >                       return 0;
> > @@ -3462,6 +3532,7 @@ static int __init hotkey_init(struct
> > ibm_init_struct *iibm)
> >       }
> >
> >       tabletsw_state = hotkey_init_tablet_mode();
> > +     keyboard_attached_on_screen_update();
> >
> >       /* Set up key map */
> >       keymap_id = tpacpi_check_quirks(tpacpi_keymap_qtable,
> > @@ -3842,6 +3913,8 @@ static bool hotkey_notify_6xxx(const u32 hkey,
> > bool *send_acpi_ev)
> >       case TP_HKEY_EV_TABLET_CHANGED:
> >               tpacpi_input_send_tabletsw();
> >               hotkey_tablet_mode_notify_change();
> > +             if (keyboard_attached_on_screen_update())
> > +                     keyboard_attached_on_screen_notify_change();
> >               *send_acpi_ev = false;
> >               return true;
> >
> > @@ -3998,6 +4071,8 @@ static void hotkey_resume(void)
> >       tpacpi_send_radiosw_update();
> >       tpacpi_input_send_tabletsw();
> >       hotkey_tablet_mode_notify_change();
> > +     keyboard_attached_on_screen_update();
> > +     keyboard_attached_on_screen_notify_change();
> >       hotkey_wakeup_reason_notify_change();
> >       hotkey_wakeup_hotunplug_complete_notify_change();
> >       hotkey_poll_setup_safe(false);
> > @@ -4296,6 +4371,17 @@ static const struct dmi_system_id fwbug_list[]
> > __initconst = {
> >       {}
> >  };
> >
> > +static const struct dmi_system_id keyboard_attached_on_screen_list[]
> > __initconst = {
> > +     {
> > +             .ident = "ThinkPad X1 Fold 16 Gen 1",
> > +             .matches = {
> > +                     DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
> > +                     DMI_MATCH(DMI_PRODUCT_FAMILY, "ThinkPad X1 Fold 16 Gen 1"),
> > +             },
> > +     },
> > +     {}
> > +};
> > +
> >  static const struct pci_device_id fwbug_cards_ids[] __initconst = {
> >       { PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x24F3) },
> >       { PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0x24FD) },
> > @@ -12230,6 +12316,8 @@ static int __init
> > thinkpad_acpi_module_init(void)
> >       dmi_id = dmi_first_match(fwbug_list);
> >       if (dmi_id)
> >               tp_features.quirks = dmi_id->driver_data;
> > +     tp_features.has_keyboard_attached_on_screen =
> > +             dmi_check_system(keyboard_attached_on_screen_list);
> >
> >       /* Device initialization */
> >       tpacpi_pdev = platform_device_register_simple(TPACPI_DRVR_NAME,
> > PLATFORM_DEVID_NONE,
> > --
> > 2.43.0
>
> I'm checking to see if we have the EC spec for this platform (it's not in our Linux certification program).
>
> The code looks fine but some notes:
>  - We usually do the DMI_MATCH on the BOARD_NAME for quirks. I was checking psref.lenovo.com and there seem to be two distinct models for this platform, which is a bit confusing. I don't have a way to confirm that your changes will work for the other model so wondering if it's safer to do the quirks for 21ES/21ET or 20RL/20RK depending on what you have in hand? (I might be overthinking this too)
>  - I would have called it detachable_keyboard instead of keyboard_attached_on_screen. See what other reviewers think.
>
> If I get details back on the EC spec and confirmation it's correct I'll let you know :)
>
> Mark
>