Rework device discovery API

libusb_find_devices and libusb_get_devices are no more

libusb_get_device_list obtains a list of libusb_device structures for all
known devices in the system.

Each libusb_device now has a reference count, defaulting to 1 on
instantiation. The reference count of 1 refers to the fact that it is
present in the list in this scenario.

Opening a device adds a pointer to the libusb_device structure in the
handle, so that also adds a reference. Closing the device removes that
reference.

The function to free the device list can optionally unref all the devices
inside.

In future we will make the libusb_device instances all "global" so that if
the app calls get_device_list twice it actually gets the same libusb_device
structure references back. This way we can start to track disconnects, and
we can investigate adding a unique "session ID" to each libusb_device, an
identifier guaranteed to be unique to that device until reboot.

1 files changed, 3 insertions, 3 deletions

diff --git a/libusb/libusbi.h b/libusb/libusbi.h
index b639ed6..c6b7f3e 100644
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -143,8 +143,8 @@ void usbi_log(enum usbi_log_level, const char *function, const char *format, ...
 #define usbi_warn(fmt...) _usbi_log(LOG_LEVEL_WARNING, fmt)
 #define usbi_err(fmt...) _usbi_log(LOG_LEVEL_ERROR, fmt)
 
-struct libusb_dev {
-	struct list_head list;
+struct libusb_device {
+	int refcnt;
 	char *nodepath;
 	struct libusb_dev_descriptor desc;
 	struct libusb_config_descriptor *config;
@@ -152,7 +152,7 @@ struct libusb_dev {
 
 struct libusb_dev_handle {
 	struct list_head list;
-	struct libusb_dev *dev;
+	struct libusb_device *dev;
 	int fd;
 };