Allow computation of max report size for other types

Author: Stephen

libusb/hid.c

@@ -69,6 +69,12 @@ extern "C" {
 #define DETACH_KERNEL_DRIVER
 #endif
 
+enum report_descr_type : uint8_t {
+	REPORT_DESCR_INPUT = 0x80,
+	REPORT_DESCR_OUTPUT = 0x90,
+	REPORT_DESCR_FEATURE = 0xB0,
+};
+
 /* Uncomment to enable the retrieval of Usage and Usage Page in
 hid_enumerate(). Warning, on platforms different from FreeBSD
 this is very invasive as it requires the detach
@@ -279,17 +285,17 @@ static int get_usage(uint8_t *report_descriptor, size_t size,
 	return -1; /* failure */
 }
 
-/* Retrieves the largest input report size (in bytes) from the passed in report descriptor.
+/* Retrieves the largest report size (in bytes) from the passed in report descriptor.
    The return value is the size on success and -1 on failure. */
-static size_t get_max_input_report_size(uint8_t * report_descriptor, int desc_size)
+static size_t get_max_report_size(uint8_t * report_descriptor, int desc_size, enum report_descr_type report_type)
 {
 	int i = 0;
 	int size_code;
 	int data_len, key_size;
 
 	int64_t report_size = -1, report_count = -1;
-	ssize_t cur_size = 0;
-	ssize_t max_size = -1;
+	size_t cur_size = 0;
+	size_t max_size = 0;
 
 	while (i < desc_size) {
 		int key = report_descriptor[i];
@@ -322,7 +328,7 @@ static size_t get_max_input_report_size(uint8_t * report_descriptor, int desc_si
 		if (key_cmd == 0x74) { /* Report Size */
 			report_size = get_bytes(report_descriptor, desc_size, data_len, i);
 		}
-		if (key_cmd == 0x80) { /* Input */
+		if (key_cmd == report_type) { /* Input / Output / Feature */
 			if (report_count < 0 || report_size < 0) {
 				/* We are missing size or count. That isn't good. */
 				return 0;
@@ -344,13 +350,14 @@ static size_t get_max_input_report_size(uint8_t * report_descriptor, int desc_si
 		max_size = cur_size;
 	}
 
-	if (max_size < 0) {
-		return -1;
+	if (max_size == 0) {
+		// No matching reports found
+		return 0;
+	} else {
+		/* report_size is in bits. Determine the total size convert to bytes
+		(rounded up), and add one byte for the report number. */
+		return ((max_size + 7) / 8) + 1;
 	}
-
-	/* report_size is in bits. Determine the total size convert to bytes
-	   (rounded up), and add one byte for the report number. */
-	return ((max_size + 7) / 8) + 1;
 }
 
 #if defined(__FreeBSD__) && __FreeBSD__ < 10
@@ -1305,7 +1312,7 @@ static int hidapi_initialize_device(hid_device *dev, const struct libusb_interfa
 
 	int desc_size = hid_get_report_descriptor_libusb(dev->device_handle, dev->interface, dev->report_descriptor_size, report_descriptor, sizeof(report_descriptor));
 	if (desc_size > 0) {
-		dev->max_input_report_size = get_max_input_report_size(report_descriptor, desc_size);
+		dev->max_input_report_size = get_max_report_size(report_descriptor, desc_size, REPORT_DESCR_INPUT);
 	} else {
 		dev->max_input_report_size = -1;
 	}

libusb/test/max_input_report_size_test.c

@@ -7,7 +7,13 @@
 
 #include "../hid.c"
 
-static ssize_t parse_max_input_report_size(const char * filename)
+struct max_report_sizes {
+    size_t input;
+    size_t output;
+    size_t feature;
+};
+
+static int parse_max_input_report_size(const char * filename, struct max_report_sizes * sizes)
 {
 	FILE* file = fopen(filename, "r");
 	if (file == NULL) {
@@ -20,16 +26,20 @@ static ssize_t parse_max_input_report_size(const char * filename)
 		while (fgets(line, sizeof(line), file) != NULL) {
 			unsigned short temp_ushort;
 			if (sscanf(line, "pp_data->caps_info[0]->ReportByteLength   = %hu\n", &temp_ushort) == 1) {
-				fclose(file);
-				return (ssize_t)temp_ushort;
+				sizes->input = (size_t)temp_ushort;
+			}
+			if (sscanf(line, "pp_data->caps_info[1]->ReportByteLength   = %hu\n", &temp_ushort) == 1) {
+				sizes->output = (size_t)temp_ushort;
+			}
+			if (sscanf(line, "pp_data->caps_info[2]->ReportByteLength   = %hu\n", &temp_ushort) == 1) {
+				sizes->feature = (size_t)temp_ushort;
 			}
 		}
 	}
 
-	fprintf(stderr, "Unable to find pp_data->caps_info[0]->ReportByteLength in %s\n", filename);
 	fclose(file);
 
-	return -1;
+	return 0;
 }
 
 static bool read_hex_data_from_text_file(const char *filename, unsigned char *data_out, size_t data_size, size_t *actual_read)
@@ -97,19 +107,36 @@ int main(int argc, char* argv[])
 		return EXIT_FAILURE;
 	}
 
-	ssize_t expected = parse_max_input_report_size(argv[1]);
-	if (expected < 0) {
-		fprintf(stderr, "Unable to expected max input report size from %s\n", argv[1]);
+        struct max_report_sizes expected;
+	if (parse_max_input_report_size(argv[1], &expected) < 0) {
+		fprintf(stderr, "Unable to get expected max report sizes from %s\n", argv[1]);
 		return EXIT_FAILURE;
 	}
 
-	ssize_t res = (ssize_t)get_max_input_report_size(report_descriptor, report_descriptor_size);
+	struct max_report_sizes computed = {
+		.input = (size_t)get_max_report_size(report_descriptor, report_descriptor_size, REPORT_DESCR_INPUT),
+		.output = (size_t)get_max_report_size(report_descriptor, report_descriptor_size, REPORT_DESCR_OUTPUT),
+		.feature = (size_t)get_max_report_size(report_descriptor, report_descriptor_size, REPORT_DESCR_FEATURE)
+	};
 
-	if (res != expected) {
-		fprintf(stderr, "Failed to properly compute size. Got %zd, expected %zd\n", res, expected);
-		return EXIT_FAILURE;
-	} else {
-		printf("Properly computed size: %zd\n", res);
-		return EXIT_SUCCESS;
+	int ret = EXIT_SUCCESS;
+
+	if (expected.input != computed.input) {
+		fprintf(stderr, "Failed to properly compute input size. Got %zu, expected %zu\n", computed.input, expected.input);
+		ret = EXIT_FAILURE;
 	}
+	if (expected.output != computed.output) {
+		fprintf(stderr, "Failed to properly compute output size. Got %zu, expected %zu\n", computed.output, expected.output);
+		ret = EXIT_FAILURE;
+	}
+	if (expected.feature != computed.feature) {
+		fprintf(stderr, "Failed to properly compute feature size. Got %zu, expected %zu\n", computed.feature, expected.feature);
+		ret = EXIT_FAILURE;
+	}
+
+	if (ret == EXIT_SUCCESS) {
+		printf("Properly computed sizes: %zu, %zu, %zu\n", computed.input, computed.output, computed.feature);
+	}
+
+	return ret;
 }