issue with ftdi stream on FT2232H

[Michal B <developer.m3@xxxxxxxxx>]

Dear development team,

i'm having issue with ftdi stream function ...

i upgraded my linux to debian 11 bullseye , might be old at this moment but there is issue with recent version of libftdi1 ,

my kernel is

5.10.0-32-amd64 #1 SMP Debian 5.10.223-1 (2024-08-10) x86_64 GNU/Linux

in debian i have:

libftdi1-2:amd64  .... 1.5-5+b1

libusb-1.0-0:amd64 ....   2:1.0.24-3

first i tried stream_test.c from examples, i got error -2 ... not usable anymore ...

then i used source code ftdi_stream.c,

i found that call of libusb_handle_events_timeout(ftdi->usb_ctx, &timeout);

is too short to be timeouted , i found that

struct timeval timeout = { 0, ftdi->usb_read_timeout * 1000};

is evaluated to value: { 0, 5000 * 1000}; .... the question is : is it acceptable to set timeout { 0 sec, 5M usec } and not { 5 sec, 0 usec } ?

possibly it could be ignored to zero timeout ...

then i found that bInterval is zero ( during open device and try to stream read ):

# lsusb -v -d 0403:6010 | grep -E '(iInterface|bInterval)'
      iInterface              2 USB <-> Serial Converter XX FPGA
        bInterval               0
        bInterval               0
      iInterface              2 USB <-> Serial Converter XX FPGA
        bInterval               0
        bInterval               0

in my code i call ftdi_set_latency_timer(ftdi_handle, 2) as it is in example ...

this means that bInterval ( latency_timer ) is reset afterwards during read stream for some reason,

i found that reset is possibly after each timeout of libusb_handle_events_timeout();

so i tried call ftdi_set_latency_timer(ftdi_handle, 2) before each libusb_handle_events_timeout() and i got some streaming ...

i hope my information helps to improve libftdi1 ...

Kind regards ...

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