[libusb] [PATCH 4/7] core: Add libusb_wrap_sys_device() API

[Vianney le C. de Saint-M. <co...@qu...>]

Introduce a new API function for wrapping an existing platform-specific
device handle as a libusb_device_handle.

Signed-off-by: Vianney le Clément de Saint-Marcq <co...@qu...>
---
 libusb/core.c    | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
 libusb/libusb.h  |  1 +
 libusb/libusbi.h | 28 +++++++++++++++++++
 3 files changed, 101 insertions(+)

diff --git a/libusb/core.c b/libusb/core.c
index 8cb598d7..f839b6a3 100644
--- a/libusb/core.c
+++ b/libusb/core.c
@@ -1215,6 +1215,78 @@ int usbi_clear_event(struct libusb_context *ctx)
 	return 0;
 }
 
+/** \ingroup libusb_dev
+ * Wrap a platform-specific system device handle and obtain a libusb device
+ * handle for the underlying device. The handle allows you to use libusb to
+ * perform I/O on the device in question.
+ *
+ * On Linux, the system device handle must be a valid file descriptor opened
+ * on the device node.
+ *
+ * The system device handle must remain open until libusb_close() is called.
+ * The system device handle will not be closed by libusb_close().
+ *
+ * Internally, this function creates a temporary device and makes it
+ * available to you through libusb_get_device(). This device is destroyed
+ * during libusb_close(). The device shall not be opened through libusb_open().
+ *
+ * This is a non-blocking function; no requests are sent over the bus.
+ *
+ * \param ctx the context to operate on, or NULL for the default context
+ * \param sys_dev the platform-specific system device handle
+ * \param dev_handle output location for the returned device handle pointer. Only
+ * populated when the return code is 0.
+ * \returns 0 on success
+ * \returns LIBUSB_ERROR_NO_MEM on memory allocation failure
+ * \returns LIBUSB_ERROR_ACCESS if the user has insufficient permissions
+ * \returns LIBUSB_ERROR_NOT_SUPPORTED if the operation is not supported on this
+ * platform
+ * \returns another LIBUSB_ERROR code on other failure
+ */
+int API_EXPORTED libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev,
+	libusb_device_handle **dev_handle)
+{
+	struct libusb_device_handle *_dev_handle;
+	size_t priv_size = usbi_backend.device_handle_priv_size;
+	int r;
+	usbi_dbg("wrap_sys_device %p", sys_dev);
+
+	USBI_GET_CONTEXT(ctx);
+
+	if (!usbi_backend.wrap_sys_device)
+		return LIBUSB_ERROR_NOT_SUPPORTED;
+
+	_dev_handle = malloc(sizeof(*_dev_handle) + priv_size);
+	if (!_dev_handle)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = usbi_mutex_init(&_dev_handle->lock);
+	if (r) {
+		free(_dev_handle);
+		return LIBUSB_ERROR_OTHER;
+	}
+
+	_dev_handle->dev = NULL;
+	_dev_handle->auto_detach_kernel_driver = 0;
+	_dev_handle->claimed_interfaces = 0;
+	memset(&_dev_handle->os_priv, 0, priv_size);
+
+	r = usbi_backend.wrap_sys_device(ctx, _dev_handle, sys_dev);
+	if (r < 0) {
+		usbi_dbg("wrap_sys_device %p returns %d", sys_dev, r);
+		usbi_mutex_destroy(&_dev_handle->lock);
+		free(_dev_handle);
+		return r;
+	}
+
+	usbi_mutex_lock(&ctx->open_devs_lock);
+	list_add(&_dev_handle->list, &ctx->open_devs);
+	usbi_mutex_unlock(&ctx->open_devs_lock);
+	*dev_handle = _dev_handle;
+
+	return 0;
+}
+
 /** \ingroup libusb_dev
  * Open a device and obtain a device handle. A handle allows you to perform
  * I/O on the device in question.
diff --git a/libusb/libusb.h b/libusb/libusb.h
index a81209a4..12298273 100644
--- a/libusb/libusb.h
+++ b/libusb/libusb.h
@@ -1387,6 +1387,7 @@ int LIBUSB_CALL libusb_get_max_packet_size(libusb_device *dev,
 int LIBUSB_CALL libusb_get_max_iso_packet_size(libusb_device *dev,
 	unsigned char endpoint);
 
+int LIBUSB_CALL libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev, libusb_device_handle **dev_handle);
 int LIBUSB_CALL libusb_open(libusb_device *dev, libusb_device_handle **dev_handle);
 void LIBUSB_CALL libusb_close(libusb_device_handle *dev_handle);
 libusb_device * LIBUSB_CALL libusb_get_device(libusb_device_handle *dev_handle);
diff --git a/libusb/libusbi.h b/libusb/libusbi.h
index da54ff18..60182e96 100644
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -702,6 +702,34 @@ struct usbi_os_backend {
 	 */
 	void (*hotplug_poll)(void);
 
+	/* Wrap a platform-specific device handle for I/O and other USB
+	 * operations. The device handle is preallocated for you.
+	 *
+	 * Your backend should allocate any internal resources required for I/O
+	 * and other operations so that those operations can happen (hopefully)
+	 * without hiccup. This is also a good place to inform libusb that it
+	 * should monitor certain file descriptors related to this device -
+	 * see the usbi_add_pollfd() function.
+	 *
+	 * Your backend should also initialize the device structure
+	 * (dev_handle->dev), which is NULL at the beginning of the call.
+	 *
+	 * This function should not generate any bus I/O and should not block.
+	 *
+	 * This function is called when the user attempts to wrap an existing
+	 * platform-specific device handle for a device.
+	 *
+	 * Return:
+	 * - 0 on success
+	 * - LIBUSB_ERROR_ACCESS if the user has insufficient permissions
+	 * - another LIBUSB_ERROR code on other failure
+	 *
+	 * Do not worry about freeing the handle on failed open, the upper layers
+	 * do this for you.
+	 */
+	int (*wrap_sys_device)(struct libusb_context *ctx,
+		struct libusb_device_handle *dev_handle, intptr_t sys_dev);
+
 	/* Open a device for I/O and other USB operations. The device handle
 	 * is preallocated for you, you can retrieve the device in question
 	 * through handle->dev.
-- 
2.19.2