Incorrect usage of return value in flash_file method

[TheColector]

Hi,
I just found the following code inconsistency compared to what is stated both in DLL API and flash_file code documentation.

In flash_file documentation on return value, it says:

pylink/pylink/jlink.py

Lines 2248 to 2249 in 9a06468

	Returns:
	Integer value greater than or equal to zero. Has no significance.

Whereas, in code, it retreives the number of bytes written from DLL function called JLINK_DownloadFile - which actually does not return the number of bytes written, it returns either one of 6 status values (< 0 ) when error happens, or returns status ( > 0 ) when everything went OK

pylink/pylink/jlink.py

Lines 2273 to 2278 in 9a06468

	# Program the target.
	bytes_flashed = self._dll.JLINK_DownloadFile(path.encode(), addr)
	if bytes_flashed < 0:
	raise errors.JLinkFlashException(bytes_flashed)
	return bytes_flashed

Unless I'm interpreting something wrong here, it might be some leftover from flash method implementation:

pylink/pylink/jlink.py

Lines 2224 to 2230 in 9a06468

	bytes_flashed = self._dll.JLINKARM_WriteMem(addr, len(data), data)
	res = self._dll.JLINKARM_EndDownload()
	if res < 0:
	raise errors.JLinkEraseException(res)
	return bytes_flashed

In this case, it uses different DLL API call and it returns the number of bytes written, so this is correct.
I can make a PR with fix for that, but wanted to ask first if it's really a bug or there is some other reason for behind that.

[hkpeprah]

You're right. We should just return the len(data) on success. Would gladly welcome a PR to fix this!