Linux: fix caching of active configuration for non-sysfs

4 files changed, 41 insertions, 22 deletions

diff --git a/TODO b/TODO
index 2b53246..f1e4345 100644
--- a/TODO
+++ b/TODO
@@ -5,7 +5,6 @@ review functionality missing over 0.1
 endianness of control setup, issues when resubmitting transfers
 serialization of handle_events
 internal docs for OS porters
-configuration handling
 check which messages are sent during open, claim interface, close, release
 unconfigured devices
 
diff --git a/libusb/descriptor.c b/libusb/descriptor.c
index 8814ced..f545c7f 100644
--- a/libusb/descriptor.c
+++ b/libusb/descriptor.c
@@ -557,6 +557,32 @@ err:
 	return NULL;
 }
 
+/* iterate through all configurations, returning the index of the configuration
+ * matching a specific bConfigurationValue in the idx output parameter, or -1
+ * if the config was not found.
+ * returns 0 or a LIBUSB_ERROR code
+ */
+int usbi_get_config_index_by_value(struct libusb_device *dev,
+	uint8_t bConfigurationValue, int *idx)
+{
+	int i;
+
+	usbi_dbg("value %d", bConfigurationValue);
+	for (i = 0; i < dev->num_configurations; i++) {
+		unsigned char tmp[6];
+		int r = usbi_backend->get_config_descriptor(dev, i, tmp, sizeof(tmp));
+		if (r < 0)
+			return r;
+		if (tmp[5] == bConfigurationValue) {
+			*idx = i;
+			return 0;
+		}
+	}
+
+	*idx = -1;
+	return 0;
+}
+
 /** \ingroup desc
  * Get a USB configuration descriptor with a specific bConfigurationValue.
  * This is a non-blocking function which does not involve any requests being
@@ -575,26 +601,12 @@ API_EXPORTED
 struct libusb_config_descriptor *libusb_get_config_descriptor_by_value(
 	libusb_device *dev, uint8_t bConfigurationValue)
 {
-	int i;
-	int r;
-	int found = -1;
-
-	usbi_dbg("value %d", bConfigurationValue);
-	for (i = 0; i < dev->num_configurations; i++) {
-		unsigned char tmp[6];
-		r = usbi_backend->get_config_descriptor(dev, i, tmp, sizeof(tmp));
-		if (r < 0)
-			return NULL;
-		if (tmp[5] == bConfigurationValue) {
-			found = 1;
-			break;
-		}
-	}
-
-	if (!found)
+	int idx;
+	int r = usbi_get_config_index_by_value(dev, bConfigurationValue, &idx);
+	if (r < 0 || idx == -1)
 		return NULL;
 	else
-		return libusb_get_config_descriptor(dev, i);
+		return libusb_get_config_descriptor(dev, idx);
 }
 
 /** \ingroup desc
diff --git a/libusb/libusbi.h b/libusb/libusbi.h
index c807903..a59a5e6 100644
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -229,6 +229,8 @@ void usbi_handle_transfer_completion(struct usbi_transfer *itransfer,
 void usbi_handle_transfer_cancellation(struct usbi_transfer *transfer);
 
 int usbi_parse_descriptor(unsigned char *source, char *descriptor, void *dest);
+int usbi_get_config_index_by_value(struct libusb_device *dev,
+	uint8_t bConfigurationValue, int *idx);
 
 /* polling */
 
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 957900a..4c0fb41 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -383,10 +383,16 @@ static int cache_active_config(struct libusb_device *dev, int fd,
 	struct libusb_config_descriptor config;
 	unsigned char tmp[8];
 	unsigned char *buf;
+	int idx;
 	int r;
 
-	/* FIXME */
-	r = get_config_descriptor(fd, active_config, tmp, sizeof(tmp));
+	r = usbi_get_config_index_by_value(dev, active_config, &idx);
+	if (r < 0)
+		return r;
+	if (idx == -1)
+		return LIBUSB_ERROR_NOT_FOUND;
+
+	r = get_config_descriptor(fd, idx, tmp, sizeof(tmp));
 	if (r < 0) {
 		usbi_err("first read error %d", r);
 		return r;
@@ -397,7 +403,7 @@ static int cache_active_config(struct libusb_device *dev, int fd,
 	if (!buf)
 		return LIBUSB_ERROR_NO_MEM;
 
-	r = get_config_descriptor(fd, active_config, buf, config.wTotalLength);
+	r = get_config_descriptor(fd, idx, buf, config.wTotalLength);
 	if (r < 0) {
 		free(buf);
 		return r;