HID: pidff: Factor out code for setting gain

Makes it possible to easily set gain from inside hid-pidff.c

Changes in v7:
- Check if device gain field exists before setting device gain

Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>
Reviewed-by: Michał Kopeć <michal@nozomi.space>
Reviewed-by: Paul Dino Jones <paul@spacefreak18.xyz>
Tested-by: Paul Dino Jones <paul@spacefreak18.xyz>
Tested-by: Cristóferson Bueno <cbueno81@gmail.com>
Tested-by: Pablo Cisneros <patchkez@protonmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

Author: Lawstorant

drivers/hid/usbhid/hid-pidff.c

@@ -539,6 +539,19 @@ static int pidff_needs_set_ramp(struct ff_effect *effect, struct ff_effect *old)
 	       effect->u.ramp.end_level != old->u.ramp.end_level;
 }
 
+/*
+ * Set device gain
+ */
+static void pidff_set_gain_report(struct pidff_device *pidff, u16 gain)
+{
+	if (!pidff->device_gain[PID_DEVICE_GAIN_FIELD].field)
+		return;
+
+	pidff_set(&pidff->device_gain[PID_DEVICE_GAIN_FIELD], gain);
+	hid_hw_request(pidff->hid, pidff->reports[PID_DEVICE_GAIN],
+			HID_REQ_SET_REPORT);
+}
+
 /*
  * Clear device control report
  */
@@ -865,11 +878,7 @@ static int pidff_upload_effect(struct input_dev *dev, struct ff_effect *effect,
  */
 static void pidff_set_gain(struct input_dev *dev, u16 gain)
 {
-	struct pidff_device *pidff = dev->ff->private;
-
-	pidff_set(&pidff->device_gain[PID_DEVICE_GAIN_FIELD], gain);
-	hid_hw_request(pidff->hid, pidff->reports[PID_DEVICE_GAIN],
-			HID_REQ_SET_REPORT);
+	pidff_set_gain_report(dev->ff->private, gain);
 }
 
 static void pidff_autocenter(struct pidff_device *pidff, u16 magnitude)
@@ -1404,12 +1413,7 @@ int hid_pidff_init_with_quirks(struct hid_device *hid, __u32 initial_quirks)
 	if (error)
 		goto fail;
 
-	if (test_bit(FF_GAIN, dev->ffbit)) {
-		pidff_set(&pidff->device_gain[PID_DEVICE_GAIN_FIELD], 0xffff);
-		hid_hw_request(hid, pidff->reports[PID_DEVICE_GAIN],
-				     HID_REQ_SET_REPORT);
-	}
-
+	pidff_set_gain_report(pidff, 0xffff);
 	error = pidff_check_autocenter(pidff, dev);
 	if (error)
 		goto fail;