[PATCH v2] platform/x86: thinkpad_acpi: psensor interface

[Mark Pearson <markpearson-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>]

Some Lenovo Thinkpad platforms are equipped with a 'palm sensor' so as
to be able to determine if a user is physically proximate to the device.

This patch provides the ability to retrieve the psensor state via sysfs
entrypoints and will be used by userspace for WWAN functionality to
control the transmission level safely

Co-developed-by: Nitin Joshi <njoshi1-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>
Signed-off-by: Nitin Joshi <njoshi1-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>
Signed-off-by: Mark Pearson <markpearson-6jq1YtArVR3QT0dZR+AlfA@public.gmane.org>
---
Changes in v2:
 - addressed formatting and coding style errors identified during review

 drivers/platform/x86/thinkpad_acpi.c | 107 ++++++++++++++++++++++++++-
 1 file changed, 104 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
index 4864a5c189d4..41b75dd4755c 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -4079,10 +4079,9 @@ static bool hotkey_notify_6xxx(const u32 hkey,
 
 	case TP_HKEY_EV_PALM_DETECTED:
 	case TP_HKEY_EV_PALM_UNDETECTED:
-		/* palm detected hovering the keyboard, forward to user-space
-		 * via netlink for consumption */
+		/* palm detected - pass on to event handler */
+		tpacpi_driver_event(hkey);
 		return true;
-
 	default:
 		/* report simply as unknown, no sensor dump */
 		return false;
@@ -9916,6 +9915,99 @@ static struct ibm_struct dytc_driver_data = {
 	.exit = dytc_exit,
 };
 
+/**********************************************************************
+ * Palm sensor subdriver
+ */
+
+#define PSENSOR_PRESENT_BIT 0 /* Determine if psensor present */
+#define PSENSOR_ON_BIT      1 /* psensor status */
+
+static bool psensor_state;
+
+static void psensor_notify_change(void)
+{
+	sysfs_notify(&tpacpi_pdev->dev.kobj, NULL, "psensor_state");
+}
+
+static int psensor_get(bool *state)
+{
+	acpi_handle psensor_handle;
+	int output;
+
+	if (ACPI_FAILURE(acpi_get_handle(hkey_handle, "GPSS", &psensor_handle)))
+		return -ENODEV;
+
+	if (!acpi_evalf(psensor_handle, &output, NULL, "d"))
+		return -EIO;
+
+	/* Check if sensor has a Psensor */
+	if (!(output & BIT(PSENSOR_PRESENT_BIT)))
+		return -ENODEV;
+
+	/* Return if psensor is set or not */
+	*state = output & BIT(PSENSOR_ON_BIT) ? true : false;
+	return 0;
+}
+
+static void psensor_state_refresh(void)
+{
+	bool new_state;
+	int err;
+
+	err = psensor_get(&new_state);
+	if (err || (new_state == psensor_state))
+		return;
+
+	psensor_state = new_state;
+	psensor_notify_change();
+}
+
+/* sysfs psensor entry */
+static ssize_t psensor_state_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	return sprintf(buf, "%d\n", psensor_state);
+}
+static DEVICE_ATTR_RO(psensor_state);
+
+static struct attribute *psensor_attributes[] = {
+	&dev_attr_psensor_state.attr,
+	NULL
+};
+
+static const struct attribute_group psensor_attr_group = {
+	.attrs = psensor_attributes,
+};
+
+static int tpacpi_psensor_init(struct ibm_init_struct *iibm)
+{
+	int err;
+
+	err = psensor_get(&psensor_state);
+	/*
+	 * If support isn't available (ENODEV) then don't return an error,
+	 * just don't create the sysfs group.
+	 */
+	if (err == -ENODEV)
+		return 0;
+	/* For all other errors we can flag the failure */
+	if (err)
+		return err;
+
+	return sysfs_create_group(&tpacpi_pdev->dev.kobj, &psensor_attr_group);
+}
+
+static void psensor_exit(void)
+{
+	sysfs_remove_group(&tpacpi_pdev->dev.kobj, &psensor_attr_group);
+}
+
+static struct ibm_struct psensor_driver_data = {
+	.name = "psensor",
+	.exit = psensor_exit,
+};
+
 /****************************************************************************
  ****************************************************************************
  *
@@ -9967,6 +10059,10 @@ static void tpacpi_driver_event(const unsigned int hkey_event)
 	if (hkey_event == TP_HKEY_EV_THM_CSM_COMPLETED)
 		dytc_lapmode_refresh();
 
+	if ((hkey_event == TP_HKEY_EV_PALM_DETECTED) ||
+		(hkey_event == TP_HKEY_EV_PALM_UNDETECTED))
+		psensor_state_refresh();
+
 }
 
 static void hotkey_driver_event(const unsigned int scancode)
@@ -10409,6 +10505,11 @@ static struct ibm_init_struct ibms_init[] __initdata = {
 		.init = tpacpi_dytc_init,
 		.data = &dytc_driver_data,
 	},
+	{
+		.init = tpacpi_psensor_init,
+		.data = &psensor_driver_data,
+	},
+
 };
 
 static int __init set_ibm_param(const char *val, const struct kernel_param *kp)
-- 
2.26.2