Bug in rtl-sdr / libusb / usbfs

Hello! This is my first time using this mailing list, hope it's the right place to post this. I compiled rtl-sdr under Debian 7.2 (32 bits x86) it detects my ezcap e4k properly but it's unable to read samples. When running rtl_sdr like this, it just hangs: ---8<-------------------------------------------------------------------------------------------- % rtl_sdr -f 100000000 - Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: Using device 0: Generic RTL2832U OEM Found Elonics E4000 tuner Tuned to 100000000 Hz. Reading samples in async mode... ---8<-------------------------------------------------------------------------------------------- Pressing Ctrl+C only makes rdl_sdr say "Signal caught, exiting!", but it won't exit unless you kill it explicitly with SIGKILL. If I run it in synchronous mode, I get this output instead: ---8<-------------------------------------------------------------------------------------------- % rtl_sdr -f 100000000 -S - Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: Using device 0: Generic RTL2832U OEM Found Elonics E4000 tuner Tuned to 100000000 Hz. Reading samples in sync mode... WARNING: sync read failed. Library error -8, exiting... rtlsdr_demod_write_reg failed with -1 ---8<-------------------------------------------------------------------------------------------- I tried to reinstall libusb, recompiling it from a newer version (I'm currently using 1.0-16rc10) and got the same output. As -8 means overflow for libusb, I decided to increase the output block size. I had to edit rtl_sdr.c to read as much as 30M, and that was the only way I could get some output. Block sizes below 10M just won't do the trick: ---8<-------------------------------------------------------------------------------------------- % rtl_sdr -b 30000000 -f 100000000 -S - Found 1 device(s): 0: Realtek, RTL2838UHIDIR, SN: Using device 0: Generic RTL2832U OEM Found Elonics E4000 tuner Tuned to 100000000 Hz. Reading samples in sync mode... Short read, samples lost, exiting! Library error 0, exiting... (here be messy bytes of 64 bytes sampled by RTL) ---8<-------------------------------------------------------------------------------------------- That's why I recompiled libusb with logging, and I got this output (now, with 3M blocks): ---8<-------------------------------------------------------------------------------------------- [...] Reading samples in sync mode... libusb: 1.079895 debug [submit_bulk_transfer] need 184 urbs for new transfer with length 3000000 libusb: 1.080660 debug [libusb_handle_events_timeout_completed] doing our own event handling libusb: 1.080692 debug [handle_events] poll() 4 fds with timeout in 60000ms libusb: 1.083056 debug [handle_events] poll() returned 1 libusb: 1.083082 debug [reap_for_handle] urb type=3 status=-75 transferred=64 libusb: 1.083104 debug [handle_bulk_completion] handling completion status -75 of bulk urb 1/184 libusb: 1.083125 debug [handle_bulk_completion] overflow, actual_length=64 libusb: 1.083146 debug [disarm_timerfd] libusb: 1.083161 debug [usbi_handle_transfer_completion] transfer 0x97a0424 has callback 0xb775c7f0 libusb: 1.083182 debug [bulk_transfer_cb] actual_length=64 WARNING: sync read failed. Library error -8, exiting... [...] ---8<-------------------------------------------------------------------------------------------- Status -75 (overflow) made me think about a limitation on the URB size in my system, but it looks that in Linux that's a standard (16K), so I ran out of ideas. I don't know where the problem is anymore, whether in rtl-sdr, libusb, usbfs or even in my system; because I've compiled it in two different systems already (my laptop - Ubuntu 12.04 - and my home computer - Debian Sid -) and it works fine in both of them. Regards, --