Lenovo ThinkPad systems support the prevention of
battery charging via a manual override called Inhibit Charge.

This patch adds support for that attribute and exposes it via the
battery ACPI driver in the generic location:

/sys/class/power_supply/BATX/inhibit_charge

Signed-off-by: Ognjen Galic <smclt...@gmail.com>
---
 drivers/platform/x86/thinkpad_acpi.c | 66 +++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/thinkpad_acpi.c 
b/drivers/platform/x86/thinkpad_acpi.c
index da1ca485..b8b74889 100644
--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -9233,6 +9233,11 @@ static struct ibm_struct mute_led_driver_data = {
 #define GET_STOP       "BCSG"
 #define SET_STOP       "BCSS"
 
+#define SET_INHIBIT    "BICS"
+#define GET_INHIBIT    "BICG"
+
+#define INHIBIT_ATTR   "inhibit_charge"
+
 #define START_ATTR "charge_start_threshold"
 #define STOP_ATTR  "charge_stop_threshold"
 
@@ -9251,6 +9256,7 @@ enum {
        /* This is used in the get/set helpers */
        THRESHOLD_START,
        THRESHOLD_STOP,
+       INHIBIT_CHARGE
 };
 
 struct tpacpi_battery_data {
@@ -9258,6 +9264,7 @@ struct tpacpi_battery_data {
        int start_support;
        int charge_stop;
        int stop_support;
+       int inhibit_support;
 };
 
 struct tpacpi_battery_driver_data {
@@ -9315,6 +9322,13 @@ static int tpacpi_battery_get(int what, int battery, int 
*ret)
                if (*ret == 0)
                        *ret = 100;
                return 0;
+       case INHIBIT_CHARGE:
+               if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_INHIBIT, ret, 
battery))
+                       return -ENODEV;
+
+               /* The inhibit charge status is in the first bit */
+               *ret = *ret & 0x01;
+               return 0;
        default:
                pr_crit("wrong parameter: %d", what);
                return -EINVAL;
@@ -9343,6 +9357,21 @@ static int tpacpi_battery_set(int what, int battery, int 
value)
                        return -ENODEV;
                }
                return 0;
+       case INHIBIT_CHARGE:
+               /* When setting inhbitit charge, we set a default vaulue of
+                * always breaking on AC detach and the effective time is set to
+                * be permanent.
+                * The battery ID is in bits 4-5, 2 bits and the effective time
+                * is in bits 8-23, 2 bytes. A time of FFFF indicates forever.
+                */
+               param = value;
+               param |= battery << 4;
+               param |= 0xFFFF << 8;
+               if ACPI_FAILURE(tpacpi_battery_acpi_eval(SET_INHIBIT, &ret, 
param)) {
+                       pr_err("failed to set inhibit charge on %d", battery);
+                       return -ENODEV;
+               }
+               return 0;
        default:
                pr_crit("wrong parameter: %d", what);
                return -EINVAL;
@@ -9359,6 +9388,8 @@ static int tpacpi_battery_probe(int battery)
         * 2) Check for support
         * 3) Get the current stop threshold
         * 4) Check for support
+        * 5) Check for inhibit charge support
+        * 6) Get the current inhibit charge status
         */
        if (acpi_has_method(hkey_handle, GET_START)) {
                if ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_START, &ret, 
battery)) {
@@ -9395,10 +9426,16 @@ static int tpacpi_battery_probe(int battery)
                        return -ENODEV;
                }
        }
-       pr_info("battery %d registered (start %d, stop %d)",
+       if (acpi_has_method(hkey_handle, GET_INHIBIT))
+               if (!ACPI_FAILURE(tpacpi_battery_acpi_eval(GET_INHIBIT, &ret, 
battery)))
+                       /* Support is marked in bit 5 */
+                       battery_info.batteries[battery].inhibit_support = ret & 
BIT(5);
+
+       pr_info("battery %d registered (start %d, stop %d, inhibit: %d)",
                        battery,
                        battery_info.batteries[battery].charge_start,
-                       battery_info.batteries[battery].charge_stop);
+                       battery_info.batteries[battery].charge_stop,
+                       battery_info.batteries[battery].inhibit_support);
 
        return 0;
 }
@@ -9484,6 +9521,15 @@ static ssize_t tpacpi_battery_store(int what,
                if (tpacpi_battery_set(THRESHOLD_STOP, battery, value))
                        return -EINVAL;
                return count;
+       case INHIBIT_CHARGE:
+               if (!battery_info.batteries[battery].inhibit_support)
+                       return -ENODEV;
+               /* The only valid values are 1 and 0 */
+               if (value != 0 && value != 1)
+                       return -EINVAL;
+               if (tpacpi_battery_set(INHIBIT_CHARGE, battery, value))
+                       return -ENODEV;
+               return count;
        default:
                pr_crit("Wrong parameter: %d", what);
                return -EINVAL;
@@ -9546,12 +9592,28 @@ static ssize_t charge_stop_threshold_store(struct 
device *dev,
        return tpacpi_battery_store(THRESHOLD_STOP, dev, buf, count);
 }
 
+static ssize_t inhibit_charge_store(struct device *dev,
+                               struct device_attribute *attr,
+                               const char *buf, size_t count)
+{
+       return tpacpi_battery_store(INHIBIT_CHARGE, dev, buf, count);
+}
+
+static ssize_t inhibit_charge_show(struct device *device,
+                               struct device_attribute *attr,
+                               char *buf)
+{
+       return tpacpi_battery_show(INHIBIT_CHARGE, device, buf);
+}
+
 static DEVICE_ATTR_RW(charge_start_threshold);
 static DEVICE_ATTR_RW(charge_stop_threshold);
+static DEVICE_ATTR_RW(inhibit_charge);
 
 static struct attribute *tpacpi_battery_attrs[] = {
        &dev_attr_charge_start_threshold.attr,
        &dev_attr_charge_stop_threshold.attr,
+       &dev_attr_inhibit_charge.attr,
        NULL,
 };
 
-- 
2.17.0


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