Re: [Owfs-developers] libftdi support: take 2

Wed, 27 Jan 2016 14:47:41 -0800

Minor glitch on module/owlib/src/c/ow_ftdi.c:

here you use MIN and MAX macros, which are defined in <sys/param.h>. Don’t ask me why, but this file is not included in linux:

— form ow.h:

#ifdef HAVE_SYS_TYPES_H
#ifdef __FreeBSD__
#include <sys/param.h>
#endif /* __FreeBSD__ */
#include <sys/types.h>                  /* for stat */
#endif                                                  /* HAVE_SYS_TYPES_H */

— 

Therefore your branch won’t compile… (or better won’t link.). MIN/MAX macros are frowned upon, so maybe if you positively like them you should  define them in ow_ftdi.c or better use an inline function… like this page suggests: https://dustri.org/b/min-and-max-macro-considered-harmful.html 

Please find a patch enclosed…

As what regards the libftdi-discover I would suggest a standalone tool… could be handy also independently from OWFS.

S.

Attachment: 0001-fix-MIN-MAX-macro-problem.patch
Description: Binary data


On 27 Jan 2016, at 23:09, Johan Ström <jo...@stromnet.se> wrote:

Hi, thanks for your input!

On 27/01/16 18:40, Stefano Miccoli wrote:
Good news.

In a few days I will have an old LinkUSB available for testing, although with a limited number of sensors only: I will try-out your implementation.

Great! I've been running one LinkUSB and one DS2480B, FTDI-dongle, since I sent the email (so ~48h). Polling /uncached/alarm every 0.2s on each network, no issues.

Let me just add a few remarks.

Auto-detection (or plug and play). I’m an old Unix guy and configuration and tuning is just part of the fun: I do not see a big problem here. Explicit is better than implicit.
Agree

User space vs. kernel space. OWFS is a user space tool, and it makes sense to keep everything in user-space: direct driving of the FTDI chip is an improvement (although configuration becomes a little bit more complicated).
Well, from that point of view we're just using another interface (libusb instead of /dev/ttyXx).

Ease of use: maybe a little helper program could help: something that scans the USB bus, looks for FTDI chips, and prints the relevant libftdi description string.

Documentation: stress that the only sensible (permanent) address is s:<vendor>:<product>:<serial>. All other are basing on assumption that cannot always be met.
Instruction for the user could be:

1) unplug linkUSB
2) start libftdi-discover program
3) plug linkUSB
4) read output of libftdi-discover 
5) edit owfs.conf
Great idea!

libftdi-discover could even be (on *nix) just a couple of bash lines.
Hm, on FreeBSD I can do usbconfig dump_device_desc, on Linux I think it is lsusb? So, different tools and outputs for different OSes, suitable for humans rather than machines.
A simple libusb-based application which lists devices is only 10-15 rows or something, and would not be platform-dependent, so I'd rather use that.

Question is: build it into owserver, or standalone tool?

(libftdi *does* have a ftdi_usb_find_all but "list all" only works on libftdi >= 1.x. And it only lists devices with *known* FTDI vid/pid's. Let's say a third party device uses a FTDI chip but has obtained it's own PID (available for free from FTDI), then it would not be shown in this list. So I prefer to go with libusb and list all accessible devices, and  output some marker if it is/isn't a known FTDI device)

Johan
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