HID: add sysfs speed attribute for wacom bluetooth tablet

The attribute allows to change reporting speed of tablet from userspace through
sysfs file. The attribute is RW, valid values: 0 is low speed, 1 is high speed.
High speed is the default setting. Using low speed is a workaround if you
experience lag when using the tablet.

Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 39 insertions, 1 deletions

diff --git a/drivers/hid/hid-wacom.c b/drivers/hid/hid-wacom.c
index f9d493931b02..97ef6260fda0 100644
--- a/drivers/hid/hid-wacom.c
+++ b/drivers/hid/hid-wacom.c
@@ -30,6 +30,7 @@
 struct wacom_data {
         __u16 tool;
         unsigned char butstate;
+        unsigned char high_speed;
 #ifdef CONFIG_HID_WACOM_POWER_SUPPLY
         int battery_capacity;
         struct power_supply battery;
@@ -105,6 +106,7 @@ static int wacom_ac_get_property(struct power_supply *psy,
 
 static void wacom_poke(struct hid_device *hdev, u8 speed)
 {
+        struct wacom_data *wdata = hid_get_drvdata(hdev);
         int limit, ret;
         char rep_data[2];
 
@@ -128,8 +130,10 @@ static void wacom_poke(struct hid_device *hdev, u8 speed)
                                         HID_FEATURE_REPORT);
                 } while (ret < 0 && limit-- > 0);
 
-                if (ret >= 0)
+                if (ret >= 0) {
+                        wdata->high_speed = speed;
                         return;
+                }
         }
 
         /*
@@ -141,6 +145,35 @@ static void wacom_poke(struct hid_device *hdev, u8 speed)
         return;
 }
 
+static ssize_t wacom_show_speed(struct device *dev,
+                                struct device_attribute
+                                *attr, char *buf)
+{
+        struct wacom_data *wdata = dev_get_drvdata(dev);
+
+        return snprintf(buf, PAGE_SIZE, "%i\n", wdata->high_speed);
+}
+
+static ssize_t wacom_store_speed(struct device *dev,
+                                struct device_attribute *attr,
+                                const char *buf, size_t count)
+{
+        struct hid_device *hdev = container_of(dev, struct hid_device, dev);
+        int new_speed;
+
+        if (sscanf(buf, "%1d", &new_speed ) != 1)
+                return -EINVAL;
+
+        if (new_speed == 0 || new_speed == 1) {
+                wacom_poke(hdev, new_speed);
+                return strnlen(buf, PAGE_SIZE);
+        } else
+                return -EINVAL;
+}
+
+static DEVICE_ATTR(speed, S_IRUGO | S_IWUGO,
+                wacom_show_speed, wacom_store_speed);
+
 static int wacom_raw_event(struct hid_device *hdev, struct hid_report *report,
                 u8 *raw_data, int size)
 {
@@ -297,6 +330,11 @@ static int wacom_probe(struct hid_device *hdev,
                 goto err_free;
         }
 
+        ret = device_create_file(&hdev->dev, &dev_attr_speed);
+        if (ret)
+                dev_warn(&hdev->dev,
+                        "can't create sysfs speed attribute err: %d\n", ret);
+
         /* Set Wacom mode 2 with high reporting speed */
         wacom_poke(hdev, 1);