sm6250-common: power-libperfmgr: Scan input devices for eligible DT2W node

It is no longer a surprise for anyone to see Xiaomi shipping the same
device with different displays and different displays usually mean
different touchscreen drivers.

The current double tap handling in the power HAL only takes into
account one specific node, meant to be set in the device tree.
However, if the touchscreen was registered as a different input device
it would cause the feature to be broken. Address the issue by iterating
through the input devices in order to find one supported touchscreen
input to be used.

Co-authored-by: LuK1337 <priv.luk@gmail.com>
Change-Id: I2f7fb4a8b0c9cd1a16d6c2b93602d285a191f170

power-libperfmgr/Power.cpp

@@ -30,7 +30,6 @@
 #include "Power.h"
 #include <linux/input.h>
 
-constexpr char kWakeupEventNode[] = "/dev/input/event2";
 constexpr int kWakeupModeOff = 4;
 constexpr int kWakeupModeOn = 5;
 
@@ -141,10 +140,47 @@ Return<void> Power::powerHint(PowerHint_1_0 hint, int32_t data) {
     return Void();
 }
 
+int open_ts_input() {
+    int fd = -1;
+    DIR *dir = opendir("/dev/input");
+
+    if (dir != NULL) {
+        struct dirent *ent;
+
+        while ((ent = readdir(dir)) != NULL) {
+            if (ent->d_type == DT_CHR) {
+                char absolute_path[PATH_MAX] = {0};
+                char name[80] = {0};
+
+                strcpy(absolute_path, "/dev/input/");
+                strcat(absolute_path, ent->d_name);
+
+                fd = open(absolute_path, O_RDWR);
+                if (ioctl(fd, EVIOCGNAME(sizeof(name) - 1), &name) > 0) {
+                    if (strcmp(name, "fts_ts") == 0 ||
+                            strcmp(name, "NVTCapacitiveTouchScreen") == 0)
+                        break;
+                }
+
+                close(fd);
+                fd = -1;
+            }
+        }
+
+        closedir(dir);
+    }
+
+    return fd;
+}
+
 Return<void> Power::setFeature(Feature feature, bool activate) {
     switch (feature) {
         case Feature::POWER_FEATURE_DOUBLE_TAP_TO_WAKE: {
-            int fd = open(kWakeupEventNode, O_RDWR);
+            int fd = open_ts_input();
+            if (fd == -1) {
+                ALOGW("DT2W won't work because no supported touchscreen input devices were found");
+                return Void();
+            }
             struct input_event ev;
             ev.type = EV_SYN;
             ev.code = SYN_CONFIG;

sepolicy/vendor/hal_power_default.te

@@ -1,3 +1,3 @@
 # Allow hal_power_default to write to dt2w nodes
-allow hal_power_default input_device:dir search;
+allow hal_power_default input_device:dir r_dir_perms;
 allow hal_power_default input_device:chr_file rw_file_perms;