Add hid_set_num_input_buffers() API

.builds/freebsd.yml

@@ -40,14 +40,14 @@ tasks:
     for package in hidapi hidapi-hidraw; do
       cc -Wall -Wextra -Werror \
         $(pkg-config --cflags "$package") \
-        tests/pkg-config/test.c \
+        src/tests/pkg-config/test.c \
         -o "build/$package-pkg-config-test" \
         $(pkg-config --static --libs "$package")
       "./build/$package-pkg-config-test"
     done
     cc -Wall -Wextra -Werror \
       $(pkg-config --cflags hidapi-libusb) \
-      tests/pkg-config/test.c \
+      src/tests/pkg-config/test.c \
       -o build/hidapi-libusb-pkg-config-test \
       $(pkg-config --libs hidapi-libusb)
     ./build/hidapi-libusb-pkg-config-test

.github/workflows/builds.yml

@@ -140,12 +140,12 @@ jobs:
       run: make install
     - name: Check pkg-config package
       run: |
-        autoreconf --install --force hidapisrc/tests/pkg-config
+        autoreconf --install --force hidapisrc/src/tests/pkg-config
         mkdir -p build/pkg-config-test
         cd build/pkg-config-test
         CFLAGS="${GNU_COMPILE_FLAGS}" \
           PKG_CONFIG_PATH="${GITHUB_WORKSPACE}/install/shared/lib/pkgconfig" \
-          "${GITHUB_WORKSPACE}/hidapisrc/tests/pkg-config/configure"
+          "${GITHUB_WORKSPACE}/hidapisrc/src/tests/pkg-config/configure"
         make V=1
     - name: Run virtual-device tests (uhid -> hidraw; raw-gadget self-skips)
       working-directory: build/shared

CMakeLists.txt

@@ -91,6 +91,6 @@ if(HIDAPI_BUILD_HIDTEST)
     add_subdirectory(hidtest)
 endif()
 
-if(HIDAPI_WITH_TESTS AND (WIN32 OR CMAKE_SYSTEM_NAME MATCHES "Linux" OR APPLE))
+if(HIDAPI_WITH_TESTS)
     add_subdirectory(src/tests)
 endif()

Makefile.am

@@ -68,9 +68,10 @@ endif
 EXTRA_DIST = \
  udev \
  doxygen \
- tests/pkg-config/configure.ac \
- tests/pkg-config/Makefile.am \
- tests/pkg-config/test.c
+ src/core/hidapi_input_ring.h \
+ src/tests/pkg-config/configure.ac \
+ src/tests/pkg-config/Makefile.am \
+ src/tests/pkg-config/test.c
 
 dist_doc_DATA = \
  README.md \

freebsd/hid.c

@@ -1013,6 +1013,17 @@ HID_API_EXPORT const wchar_t * HID_API_CALL  hid_read_error(hid_device *dev)
 	return dev->read_error_str;
 }
 
+int HID_API_EXPORT HID_API_CALL hid_set_num_input_buffers(hid_device *dev, int num_buffers)
+{
+	if (num_buffers <= 0 || num_buffers > HID_API_MAX_NUM_INPUT_BUFFERS) {
+		register_device_error(dev, "num_buffers out of range");
+		return -1;
+	}
+	/* The kernel manages the input report queue. */
+	register_device_error(dev, NULL);
+	return 0;
+}
+
 int HID_API_EXPORT hid_set_nonblocking(hid_device *dev, int nonblock)
 {
 	/* Do all non-blocking in userspace using poll(), since it looks

hidapi/hidapi.h

@@ -423,6 +423,63 @@ extern "C" {
 		*/
 		int  HID_API_EXPORT HID_API_CALL hid_set_nonblocking(hid_device *dev, int nonblock);
 
+		/** @brief Upper bound for hid_set_num_input_buffers().
+
+		    Values passed above this limit are rejected by
+		    hid_set_num_input_buffers(). Guards against
+		    memory-exhaustion via unbounded input report queue growth.
+
+		    May be overridden at build time via
+		    -DHID_API_MAX_NUM_INPUT_BUFFERS=<value>.
+		    The library enforces the value used when it was built;
+		    redefining this macro only in an application does not change
+		    that limit. Build the library and application with the same
+		    value to keep the declaration and enforced limit consistent.
+		*/
+		#ifndef HID_API_MAX_NUM_INPUT_BUFFERS
+		#define HID_API_MAX_NUM_INPUT_BUFFERS 1024
+		#endif
+
+		/** @brief Set the number of input report buffers queued per device.
+
+		    Since version 0.16.0, @ref HID_API_VERSION >= HID_API_MAKE_VERSION(0, 16, 0)
+
+		    Some HID devices emit input reports in bursts at rates
+		    that exceed the default internal queue capacity, causing
+		    silent report drops on macOS and the libusb backend.
+		    This function allows callers to change how many input
+		    report buffers are retained per device.
+
+		    Call after hid_open() and before the first hid_read() to
+		    avoid losing reports buffered at open time.
+
+		    @note Per-backend behavior:
+		    - **macOS (IOKit)** and **libusb**: resizes the
+		      userspace input-report queue. Default: 30 reports.
+		      A full queue drops the oldest report. Shrinking below the
+		      queued count keeps the newest reports in FIFO order.
+		    - **Windows**: forwards to HidD_SetNumInputBuffers(),
+		      which resizes the kernel HID ring buffer. The kernel
+		      accepts values in the range [2, 512]; requests outside
+		      this range return -1. Default: 64 reports.
+		    - **Linux/FreeBSD hidraw** and **NetBSD uhid**: the call is
+		      accepted (returns 0) and validated against
+		      HID_API_MAX_NUM_INPUT_BUFFERS, but has no effect (no-op) —
+		      these kernels manage the input report buffer internally
+		      and expose no userspace resize.
+
+		    @ingroup API
+		    @param dev A device handle returned from hid_open().
+		    @param num_buffers The desired number of input report buffers.
+		        Must be in range [1, HID_API_MAX_NUM_INPUT_BUFFERS].
+
+		    @returns
+		        0 on success, -1 on failure (invalid parameters or
+		        backend-specific error). Call hid_error(dev) for
+		        details where supported.
+		*/
+		int HID_API_EXPORT HID_API_CALL hid_set_num_input_buffers(hid_device *dev, int num_buffers);
+
 		/** @brief Asynchronously interrupt blocking hid_read/hid_read_timeout call.
 
 			Since version 0.16.0, @ref HID_API_VERSION >= HID_API_MAKE_VERSION(0, 16, 0)

hidtest/test.c

@@ -144,6 +144,9 @@ int main(int argc, char* argv[])
 	(void)&hid_get_input_report;
 #if HID_API_VERSION >= HID_API_MAKE_VERSION(0, 15, 0)
 	(void)&hid_send_output_report;
+#endif
+#if HID_API_VERSION >= HID_API_MAKE_VERSION(0, 16, 0)
+	(void)&hid_set_num_input_buffers;
 #endif
 	(void)&hid_get_feature_report;
 	(void)&hid_send_feature_report;
@@ -198,6 +201,13 @@ int main(int argc, char* argv[])
  		return 1;
 	}
 
+#if HID_API_VERSION >= HID_API_MAKE_VERSION(0, 16, 0)
+	res = hid_set_num_input_buffers(handle, 500);
+	if (res < 0) {
+		printf("Unable to set input buffers: %ls\n", hid_error(handle));
+	}
+#endif
+
 #if defined(_WIN32) && HID_API_VERSION >= HID_API_MAKE_VERSION(0, 15, 0)
 	hid_winapi_set_write_timeout(handle, 5000);
 #endif