libftdi Archives

Subject: RE: [libftdi-1.0] Limit read buffer chunksize to 16384 on Linux

From: "Michael Plante" <michael.plante@xxxxxxxxx>
To: <libftdi@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 13 Feb 2010 19:33:56 -0600
Jie Zhang wrote:
>> We can't set readbuffer_chunksize larger than MAX_BULK_BUFFER_LENGTH,
>> which is defined in libusb-1.0, on Linux. Otherwise, each USB read
>> request will be divided into multiple (to be exactly, 4) URBs. The
>> last 3 URBs of these 4 URBs will usually result in abnormal reaps
>> because we usually request small number of data. The abnormal reaps
>> will concatenate empty ftdi packets to other packet on Linux kernel
>> older than 2.6.32. libftdi cannot parse such combined packet. This
>> will cause issue for UrJTAG when using libftdi-1.0 with libusb-1.0. I
>> have committed this patch on the libftdi-1.0 git tree.

In other words, the status bytes issue only happened with very large reads,
or is there something else going on that I'm missing?  If the former, I
hadn't seen that context on any of the emails...  Anyway, good catch


libftdi - see for details.
To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx   

Current Thread