DPRINTF usually is a FreeBSD specific debugging printf which needs to be enabled at compile time (not in this case) and is purely for developers. It is not uncommon to have different flags depending on what part to debug.

I do not fully understand the reasoning that prompted this change? Can you elaborate a bit more why this change is needed?

I am fixing https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=277653.

In D50680#1156990, @bz wrote:

DPRINTF usually is a FreeBSD specific debugging printf which needs to be enabled at compile time (not in this case) and is purely for developers. It is not uncommon to have different flags depending on what part to debug.

I do not fully understand the reasoning that prompted this change? Can you elaborate a bit more why this change is needed?

The libusb provides libusb_set_debug to decide which level is the debug output.

See: https://github.com/libusb/libusb/blob/15a7ebb4d426c5ce196684347d2b7cafad862626/libusb/core.c#L2213

However, the meaning of "level" in FreeBSD libusb is different from the original implementation. The original implementation indicate the critical level on the message instead of the FreeBSD one, which indicates the source where the error emit.

This cause the application would like to set debug level (like stlink) unable to use the correct level because they do not have the same meaning.

I think this is a API incompatible between these two different version of libusb.

Also, it seems that the DPRINTF in FreeBSD libusb is not a compile time macro as

		if ((ctx)->debug & LIBUSB_DEBUG_FUNCTION) {	\
			printf("LIBUSB_FUNCTION: "		\
			       format "\n", ## __VA_ARGS__);	\
		}

ctx->debug can be set at runtime by libusb_set_debug.

@bz Is there still any concern about this patch? @bapt and what is your opinion about this?
If there is no any problem, I will prepare a github link for merging.

Please use this patch to merge. Thanks! https://github.com/aokblast/freebsd-src/commit/e404814eed946bcd6551d163dbfeeeb951bf935b.patch