input_common/sdl: only log motion capabilities when they change

On the Steam Deck the log was flooded with the same gyro message, over
3000 times in a single session.

Motion capabilities are now only logged when they change, and the sensor
restart interval grows exponentially (up to 64x) while the sensor keeps
returning zeroed data.

Tested with Pokemon Pokopia on the Steam Deck: from ~42 messages in 33s
down to 1 for the whole session, controls working normally.

Assisted-by: Claude Opus 5.5 (debugging, code, and drafting this message)

1 files changed, 23 insertions, 3 deletions

diff --git a/src/input_common/drivers/sdl_driver.cpp b/src/input_common/drivers/sdl_driver.cpp
index c3e9a066b3..a308554071 100644
--- a/src/input_common/drivers/sdl_driver.cpp
+++ b/src/input_common/drivers/sdl_driver.cpp
@@ -3,6 +3,7 @@
 // SPDX-FileCopyrightText: 2018 Citra Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
+#include <algorithm>
 #include <array>
 #include <numbers>
 #include "common/logging.h"
@@ -115,7 +116,15 @@ public:
             }
         }
 
-        LOG_INFO(Input, "Controller motion capabilities: accel={} gyro={}", has_accel, has_gyro);
+        // EnableMotion is also called to recover a stalled sensor, so only log when the reported
+        // capabilities actually change instead of on every restart.
+        if (!motion_capabilities_logged || logged_accel != has_accel || logged_gyro != has_gyro) {
+            LOG_INFO(Input, "Controller motion capabilities: accel={} gyro={}", has_accel,
+                     has_gyro);
+            motion_capabilities_logged = true;
+            logged_accel = has_accel;
+            logged_gyro = has_gyro;
+        }
     }
 
     bool HasMotion() const {
@@ -163,16 +172,21 @@ public:
         // Motion data is invalid
         if (motion.accel_x == 0 && motion.gyro_x == 0 && motion.accel_y == 0 &&
             motion.gyro_y == 0 && motion.accel_z == 0 && motion.gyro_z == 0) {
-            if (motion_error_count++ < 200) {
+            if (motion_error_count++ < motion_restart_threshold) {
                 return false;
             }
-            // Try restarting the sensor
+            // Try restarting the sensor. Back off exponentially so a sensor that keeps reporting
+            // zeros (observed on the Steam Deck) isn't toggled several times a
+            // second for the whole session.
             motion_error_count = 0;
+            motion_restart_threshold =
+                std::min(motion_restart_threshold * 2, MaxMotionRestartThreshold);
             EnableMotion();
             return false;
         }
 
         motion_error_count = 0;
+        motion_restart_threshold = InitialMotionRestartThreshold;
         motion.delta_timestamp = time_difference;
         return true;
     }
@@ -393,7 +407,13 @@ private:
     mutable std::mutex mutex;
 
     u64 last_motion_update{};
+    static constexpr std::size_t InitialMotionRestartThreshold = 200;
+    static constexpr std::size_t MaxMotionRestartThreshold = 200 * 64;
     std::size_t motion_error_count{};
+    std::size_t motion_restart_threshold{InitialMotionRestartThreshold};
+    bool motion_capabilities_logged{false};
+    bool logged_accel{false};
+    bool logged_gyro{false};
     bool has_gyro{false};
     bool has_accel{false};
     bool has_vibration{false};