fpc1020_tee: Set fingerprintd priority to max when screen is off

Give fingerprintd the highest priority (MIN_NICE) when the screen is off to
speed up fingerprint processing, and then reset its priority back to normal
when the screen is on.

There are now 2 fingerprint related processes:
 - [email protected] -> comm:[email protected]
 - com.qualcomm.qti.biometrics.fingerprint.service -> comm:erprint.service

For the match to work properly, use strstr() with "erprint".

Change-Id: Ice4a384f99ae4201b2e5e942b0c8cc16c1190f52
Co-authored-by: Fiqri Ardyansyah <[email protected]>
Signed-off-by: Panchajanya1999 <[email protected]>
Signed-off-by: Carlos Ayrton Lopez Arroyo <[email protected]>

drivers/input/fingerprint/fpc_tee/fpc1020_tee.c

@@ -851,6 +851,18 @@ static int fpc1020_request_named_gpio(struct fpc1020_data *fpc1020,
 	return 0;
 }
 
+static void set_fingerprintd_nice(int nice)
+{
+	struct task_struct *p;
+
+	read_lock(&tasklist_lock);
+	for_each_process(p) {
+		if (strstr(p->comm, "erprint"))
+			set_user_nice(p, nice);
+	}
+	read_unlock(&tasklist_lock);
+}
+
 static int fpc_fb_notif_callback(struct notifier_block *nb,
 		unsigned long val, void *data)
 {
@@ -871,9 +883,11 @@ static int fpc_fb_notif_callback(struct notifier_block *nb,
 		blank = *(int *)(evdata->data);
 		switch (blank) {
 		case MI_DRM_BLANK_POWERDOWN:
+			set_fingerprintd_nice(MIN_NICE);
 			fpc1020->fb_black = true;
 			break;
 		case MI_DRM_BLANK_UNBLANK:
+			set_fingerprintd_nice(0);
 			fpc1020->fb_black = false;
 			break;
 		default: