diff --git a/arch/arm/src/stm32h7/stm32_capture.c b/arch/arm/src/stm32h7/stm32_capture.c
index 3b740c3816..1cc71acd0c 100644
--- a/arch/arm/src/stm32h7/stm32_capture.c
+++ b/arch/arm/src/stm32h7/stm32_capture.c
@@ -217,6 +217,32 @@ static inline
 uint32_t stm32_cap_gpio(const struct stm32_cap_priv_s *priv,
                         int channel)
 {
+  if (channel < 0) /* Special case: return first available channel */
+    {
+      uint32_t gpio;
+
+      /* Try counter channel first */
+
+      gpio = stm32_cap_gpio(priv, STM32_CAP_CHANNEL_COUNTER);
+      if (gpio)
+        {
+          return gpio;
+        }
+
+      /* Then try channels 1..4 */
+
+      for (int ch = 1; ch <= 4; ch++)
+        {
+          gpio = stm32_cap_gpio(priv, ch);
+          if (gpio)
+            {
+              return gpio;
+            }
+        }
+
+      return 0; /* None found */
+    }
+
   switch (priv->base)
     {
 #ifdef CONFIG_STM32H7_TIM1_CAP
@@ -1578,7 +1604,7 @@ static inline const struct stm32_cap_priv_s * stm32_cap_get_priv(int timer)
  * Public Function - Initialization
  ****************************************************************************/
 
-struct stm32_cap_dev_s *stm32_cap_init(int timer, uint8_t channel)
+struct stm32_cap_dev_s *stm32_cap_init(int timer)
 {
   const struct stm32_cap_priv_s *priv = stm32_cap_get_priv(timer);
   uint32_t gpio;
@@ -1587,7 +1613,7 @@ struct stm32_cap_dev_s *stm32_cap_init(int timer, uint8_t channel)
     {
       stm32_cap_set_rcc(priv, true);
 
-      gpio = stm32_cap_gpio(priv, channel);
+      gpio = stm32_cap_gpio(priv, -1);
       if (gpio)
         {
           stm32_configgpio(gpio);
@@ -1601,7 +1627,7 @@ struct stm32_cap_dev_s *stm32_cap_init(int timer, uint8_t channel)
   return (struct stm32_cap_dev_s *)priv;
 }
 
-int stm32_cap_deinit(struct stm32_cap_dev_s * dev, uint8_t channel)
+int stm32_cap_deinit(struct stm32_cap_dev_s * dev)
 {
   const struct stm32_cap_priv_s *priv = (struct stm32_cap_priv_s *)dev;
   uint32_t gpio;
@@ -1612,7 +1638,7 @@ int stm32_cap_deinit(struct stm32_cap_dev_s * dev, uint8_t channel)
 
   stm32_modifyreg16(priv, STM32_BTIM_CR1_OFFSET, ATIM_CR1_CEN, 0);
 
-  gpio = stm32_cap_gpio(priv, channel);
+  gpio = stm32_cap_gpio(priv, -1);
   if (gpio)
     {
       stm32_unconfiggpio(gpio);
diff --git a/arch/arm/src/stm32h7/stm32_capture.h b/arch/arm/src/stm32h7/stm32_capture.h
index 954cd911a2..89d09b5c5f 100644
--- a/arch/arm/src/stm32h7/stm32_capture.h
+++ b/arch/arm/src/stm32h7/stm32_capture.h
@@ -204,11 +204,11 @@ struct stm32_cap_ops_s
 
 /* Power-up timer and get its structure */
 
-struct stm32_cap_dev_s *stm32_cap_init(int timer, uint8_t channel);
+struct stm32_cap_dev_s *stm32_cap_init(int timer);
 
 /* Power-down timer, mark it as unused */
 
-int stm32_cap_deinit(struct stm32_cap_dev_s *dev, uint8_t channel);
+int stm32_cap_deinit(struct stm32_cap_dev_s *dev);
 
 /****************************************************************************
  * Name: stm32_cap_initialize
@@ -228,7 +228,7 @@ int stm32_cap_deinit(struct stm32_cap_dev_s *dev, uint8_t channel);
  ****************************************************************************/
 
 #ifdef CONFIG_CAPTURE
-struct cap_lowerhalf_s *stm32_cap_initialize(int timer, uint8_t channel);
+struct cap_lowerhalf_s *stm32_cap_initialize(int timer);
 #endif
 
 #undef EXTERN
diff --git a/arch/arm/src/stm32h7/stm32_capture_lowerhalf.c b/arch/arm/src/stm32h7/stm32_capture_lowerhalf.c
index 84bbeef133..11b855dd4f 100644
--- a/arch/arm/src/stm32h7/stm32_capture_lowerhalf.c
+++ b/arch/arm/src/stm32h7/stm32_capture_lowerhalf.c
@@ -576,7 +576,7 @@ struct cap_lowerhalf_s *stm32_cap_initialize(int timer)
   /* Initialize the elements of lower half state structure */
 
   lower->started  = false;
-  lower->cap      = stm32_cap_init(timer, lower->channel);
+  lower->cap      = stm32_cap_init(timer);
 
   if (lower->cap == NULL)
     {
diff --git a/drivers/timers/capture.c b/drivers/timers/capture.c
index 7fae3d31fc..a03b84e749 100644
--- a/drivers/timers/capture.c
+++ b/drivers/timers/capture.c
@@ -472,17 +472,34 @@ int cap_register_multiple(FAR const char *devpath,
                           FAR struct cap_lowerhalf_s **lower,
                           int n)
 {
-  char fullpath[16];
+  char fullpath[32];
   int ret;
 
-  if (n < 1)
+  if (!devpath || !lower || n < 1)
     {
       return -EINVAL;
     }
 
+  size_t devlen = strlen(devpath);
+  if (devlen == 0 || devlen > sizeof(fullpath) - 2)
+    {
+      return -ENAMETOOLONG;
+    }
+
   for (int i = 0; i < n; i++)
     {
-      snprintf(fullpath, sizeof(fullpath), "%s%d", devpath, i);
+      int written = snprintf(fullpath, sizeof(fullpath), "%s%d", devpath, i);
+
+      if (written < 0)
+        {
+          return -EIO;
+        }
+
+      if ((size_t)written >= sizeof(fullpath))
+        {
+          return -ENAMETOOLONG;
+        }
+
       ret = cap_register(fullpath, lower[i]);
       if (ret < 0)
         {