libusb: implement libusb_set_option

Implement libusb_set_option for API compatibility of libusb upstream
The implementation status of each option is as following:

LIBUSB_OPTION_LOG_LEVEL: just like libusb_set_debug
LIBUSB_OPTION_LOG_CB: add callback support for DPRINTF
LIBUSB_OPTION_NO_DEVICE_DISCOVERY: disable initialization of devd and
netlink when register. Also, create no thread when registration of
callback happens.
LIBUSB_OPTION_USE_USBDK: no needed as USBDK is for Windows

Sponsored by:   The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D50818

lib/libusb/libusb.3

@@ -101,6 +101,30 @@ and
 .Fn libusb_attach_kernel_driver .
 .El
 .Pp
+.Ft int
+.Fn libusb_set_option "libusb_context *ctx" "enum libusb_option option" "...value"
+This function sets the
+.Fa option
+from the given
+.Fa value .
+When the
+.Fa ctx
+is NULL, the option will be used as the default option for later created
+.Fa ctx .
+The available options are:
+.Bl -tag -width LIBUSB_OPTION -offset indent
+.It Va LIBUSB_OPTION_LOG_LEVEL
+set the option level to the given
+.Fa value .
+.It Va LIBUSB_OPTION_USE_USBDK
+use USBDK as a libusb backend (Windows only)
+.It Va LIBUSB_OPTION_NO_DEVICE_DISCOVER
+disable the USB enumeration.
+.It Va LIBUSB_OPTION_LOG_CB
+customize default callback function with
+.Fa value .
+.El
+.Pp
 .Ft const char *
 .Fn libusb_strerror "int code"
 Get the ASCII representation of the error given by the

lib/libusb/libusb.h

@@ -291,7 +291,8 @@ enum libusb_option {
 	LIBUSB_OPTION_USE_USBDK = 1,
 	LIBUSB_OPTION_NO_DEVICE_DISCOVERY = 2,
 	LIBUSB_OPTION_WEAK_AUTHORITY = 2,
-	LIBUSB_OPTION_MAX = 3,
+	LIBUSB_OPTION_LOG_CB = 3,
+	LIBUSB_OPTION_MAX = 4,
 };
 
 /* libusb structures */
@@ -302,6 +303,11 @@ struct libusb_transfer;
 struct libusb_device_handle;
 struct libusb_hotplug_callback_handle_struct;
 
+typedef struct libusb_context libusb_context;
+
+typedef void (*libusb_log_cb)(libusb_context *ctx, enum libusb_log_level,
+    const char *str);
+
 struct libusb_pollfd {
 	int	fd;
 	short	events;
@@ -668,6 +674,7 @@ int	libusb_alloc_streams(libusb_device_handle *dev, uint32_t num_streams, unsign
 int	libusb_free_streams(libusb_device_handle *dev, unsigned char *endpoints, int num_endpoints);
 void	libusb_transfer_set_stream_id(struct libusb_transfer *transfer, uint32_t stream_id);
 uint32_t libusb_transfer_get_stream_id(struct libusb_transfer *transfer);
+int	libusb_set_option(libusb_context *ctx, enum libusb_option option, ...);
 
 #if 0
 {					/* indent fix */

lib/libusb/libusb10.c

@@ -37,6 +37,7 @@
 #include <poll.h>
 #include <pthread.h>
 #include <signal.h>
+#include <stdbool.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -293,6 +294,8 @@ libusb_init_context(libusb_context **context,
 	}
 
 	libusb10_add_pollfd(ctx, &ctx->ctx_poll, NULL, ctx->event, POLLIN);
+	ctx->log_cb = NULL;
+	ctx->no_discovery = false;
 
 	pthread_mutex_lock(&default_context_lock);
 	if (usbi_default_context == NULL) {
@@ -1897,7 +1900,11 @@ libusb_log_va_args(struct libusb_context *ctx, enum libusb_log_level level,
 
 	snprintf(new_fmt, sizeof(new_fmt), "%s: %s\n", log_prefix[level], fmt);
 	vsnprintf(buffer, sizeof(buffer), new_fmt, args);
-	fputs(buffer, stdout);
+
+	if (ctx->log_cb != NULL)
+		ctx->log_cb(ctx, level, buffer);
+	else
+		fputs(buffer, stdout);
 
 	va_end(args);
 }
@@ -1947,3 +1954,72 @@ libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev,
 {
 	return (LIBUSB_ERROR_NOT_SUPPORTED);
 }
+
+int
+libusb_set_option(libusb_context *ctx, enum libusb_option option, ...)
+{
+	int err = LIBUSB_SUCCESS;
+	enum libusb_log_level level;
+	va_list args;
+	libusb_log_cb callback;
+
+	ctx = GET_CONTEXT(ctx);
+	va_start(args, option);
+
+	switch (option) {
+	case LIBUSB_OPTION_LOG_LEVEL:
+		level = va_arg(args, enum libusb_log_level);
+		if (level < LIBUSB_LOG_LEVEL_NONE ||
+		    level > LIBUSB_LOG_LEVEL_DEBUG) {
+			err = LIBUSB_ERROR_INVALID_PARAM;
+			goto end;
+		}
+		break;
+	case LIBUSB_OPTION_LOG_CB:
+		callback = va_arg(args, libusb_log_cb);
+		break;
+	}
+
+	if (option >= LIBUSB_OPTION_MAX) {
+		err = LIBUSB_ERROR_INVALID_PARAM;
+		goto end;
+	}
+
+	/*
+	 * When it is default context, the context will be accessed by multiple
+	 * instances of libusb_context that will later be taken as the default
+	 * value when new instances are created.
+	 */
+	if (ctx == usbi_default_context)
+		CTX_LOCK(ctx);
+
+	switch (option) {
+	case LIBUSB_OPTION_LOG_LEVEL:
+		if (ctx->debug_fixed)
+			break;
+		ctx->debug = level;
+		break;
+	case LIBUSB_OPTION_LOG_CB:
+		ctx->log_cb = callback;
+		break;
+	case LIBUSB_OPTION_NO_DEVICE_DISCOVERY:
+		ctx->no_discovery = true;
+		break;
+		/*
+		 * We don't handle USBDK as it is a windows
+		 * backend specified SDK
+		 */
+	case LIBUSB_OPTION_USE_USBDK:
+		break;
+	default:
+		err = LIBUSB_ERROR_INVALID_PARAM;
+		break;
+	}
+
+	if (ctx == usbi_default_context)
+		CTX_UNLOCK(ctx);
+
+end:
+	va_end(args);
+	return (err);
+}

lib/libusb/libusb10.h

@@ -118,6 +118,8 @@ struct libusb_context {
 	libusb_pollfd_added_cb fd_added_cb;
 	libusb_pollfd_removed_cb fd_removed_cb;
 	void   *fd_cb_user_data;
+	libusb_log_cb log_cb;
+	int no_discovery;
 };
 
 struct libusb_device {

lib/libusb/libusb10_hotplug.c

@@ -348,6 +348,9 @@ int libusb_hotplug_register_callback(libusb_context *ctx,
 
 	ctx = GET_CONTEXT(ctx);
 
+	if (ctx->no_discovery)
+		return (LIBUSB_SUCCESS);
+
 	if (ctx->usb_event_mode == usb_event_none) {
 		HOTPLUG_LOCK(ctx);
 		if (!netlink_init(ctx) && !devd_init(ctx))