Ядро 2.6.9-11 (SL -4)

драйвер pl2303 подгружается без проблем.
echo 111 > /dev/ttyUSB0  (на "дисплей покупателя") зависает без резалта
В логах:
Dec 28 16:24:33 localhost kernel: usbcore: deregistering driver pl2303
Dec 28 16:24:33 localhost kernel: PL-2303 ttyUSB0: PL-2303 converter now disconnected from ttyUSB0
Dec 28 16:24:33 localhost kernel: pl2303 4-1:1.0: device disconnected
Dec 28 16:24:33 localhost kernel: drivers/usb/serial/usb-serial.c: USB Serial deregistering driver PL-2303
Dec 28 16:24:39 localhost kernel: drivers/usb/serial/usb-serial.c: USB Serial support registered for PL-2303
Dec 28 16:24:39 localhost kernel: pl2303 4-1:1.0: PL-2303 converter detected
Dec 28 16:24:39 localhost kernel: usb 4-1: PL-2303 converter now attached to ttyUSB0
Dec 28 16:24:39 localhost kernel: usbcore: registered new driver pl2303
Dec 28 16:24:39 localhost kernel: drivers/usb/serial/pl2303.c: Prolific PL2303 USB to serial adaptor driver v0.11
Dec 28 16:24:44 localhost kernel: usb 4-1: pl2303_write_bulk_callback - failed resubmitting write urb, error -1
Dec 28 16:25:53 localhost kernel: usb 4-1: USB disconnect, address 7

Можете подсказать, что делать?

dmesg (отрывок):
pl2303 4-1:1.0: device disconnected
usb 4-1: new full speed USB device using address 7
pl2303 4-1:1.0: PL-2303 converter detected
drivers/usb/serial/pl2303.c: device type: 2
usb 4-1: PL-2303 converter now attached to ttyUSB0
drivers/usb/serial/pl2303.c: pl2303_open -  port 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x0  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x1  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x0:0x1  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x1:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x2:0x44  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x8:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x9:0x0  0
drivers/usb/serial/pl2303.c: pl2303_set_termios -  port 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 0
drivers/usb/serial/pl2303.c: pl2303_set_termios - data bits = 8
drivers/usb/serial/pl2303.c: pl2303_set_termios - baud = 9600
drivers/usb/serial/pl2303.c: pl2303_set_termios - stop bits = 1
drivers/usb/serial/pl2303.c: pl2303_set_termios - parity = none
drivers/usb/serial/pl2303.c: 0x21:0x20:0:0  7
drivers/usb/serial/pl2303.c: set_control_lines - value = 3, retval = 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 8
drivers/usb/serial/pl2303.c: pl2303_open - submitting read urb
drivers/usb/serial/pl2303.c: pl2303_open - submitting interrupt urb
drivers/usb/serial/pl2303.c: pl2303_ioctl (0) cmd = 0x5401
drivers/usb/serial/pl2303.c: pl2303_ioctl not supported = 0x5401
drivers/usb/serial/pl2303.c: pl2303_close - port 0
drivers/usb/serial/pl2303.c: pl2303_close - shutting down urbs
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port 0
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - urb->status = -2
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port is closed, exiting.
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
drivers/usb/serial/pl2303.c: pl2303_read_int_callback - urb shutting down with status: -2
drivers/usb/serial/pl2303.c: set_control_lines - value = 0, retval = 0
drivers/usb/serial/pl2303.c: pl2303_open -  port 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x0  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x1  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x0:0x1  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x1:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x2:0x44  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x8:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x9:0x0  0
drivers/usb/serial/pl2303.c: pl2303_set_termios -  port 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 8
drivers/usb/serial/pl2303.c: pl2303_set_termios - data bits = 8
drivers/usb/serial/pl2303.c: pl2303_set_termios - baud = 9600
drivers/usb/serial/pl2303.c: pl2303_set_termios - stop bits = 1
drivers/usb/serial/pl2303.c: pl2303_set_termios - parity = none
drivers/usb/serial/pl2303.c: 0x21:0x20:0:0  7
drivers/usb/serial/pl2303.c: set_control_lines - value = 3, retval = 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 8
drivers/usb/serial/pl2303.c: pl2303_open - submitting read urb
drivers/usb/serial/pl2303.c: pl2303_open - submitting interrupt urb
drivers/usb/serial/pl2303.c: pl2303_write - port 0, 2 bytes
PL-2303 ttyUSB0: pl2303_write - length = 2, data = 31 31
drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
drivers/usb/serial/pl2303.c: pl2303_write - port 0, 0 bytes
drivers/usb/serial/pl2303.c: pl2303_write - port 0, 1 bytes
PL-2303 ttyUSB0: pl2303_write - length = 1, data = 0d
drivers/usb/serial/pl2303.c: pl2303_write - port 0, 1 bytes
drivers/usb/serial/pl2303.c: pl2303_write - already writing
drivers/usb/serial/pl2303.c: pl2303_close - port 0
drivers/usb/serial/pl2303.c: pl2303_close - shutting down urbs
drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - port 0
drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - Overflow in write
drivers/usb/serial/pl2303.c: pl2303_write_bulk_callback - nonzero write bulk status received: -2
usb 4-1: pl2303_write_bulk_callback - failed resubmitting write urb, error -1
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
PL-2303 ttyUSB0: pl2303_read_int_callback - length = 10, data = a1 20 00 00 00 00 02 00 02 00
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port 0
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - urb->status = -2
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port is closed, exiting.
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
drivers/usb/serial/pl2303.c: pl2303_read_int_callback - urb shutting down with status: -2
drivers/usb/serial/pl2303.c: set_control_lines - value = 0, retval = 0
drivers/usb/serial/pl2303.c: pl2303_open -  port 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x0  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0x40:0x1:0x404:0x1  0
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8484:0x0  1 - 2
drivers/usb/serial/pl2303.c: 0xc0:0x1:0x8383:0x0  1 - 0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x0:0x1  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x1:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x2:0x44  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x8:0x0  0
drivers/usb/serial/pl2303.c: 0x40:0x1:0x9:0x0  0
drivers/usb/serial/pl2303.c: pl2303_set_termios -  port 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 8
drivers/usb/serial/pl2303.c: pl2303_set_termios - data bits = 8
drivers/usb/serial/pl2303.c: pl2303_set_termios - baud = 9600
drivers/usb/serial/pl2303.c: pl2303_set_termios - stop bits = 1
drivers/usb/serial/pl2303.c: pl2303_set_termios - parity = none
drivers/usb/serial/pl2303.c: 0x21:0x20:0:0  7
drivers/usb/serial/pl2303.c: set_control_lines - value = 3, retval = 0
drivers/usb/serial/pl2303.c: 0xa1:0x21:0:0  7 - 80 25 0 0 0 0 8
drivers/usb/serial/pl2303.c: pl2303_open - submitting read urb
drivers/usb/serial/pl2303.c: pl2303_open - submitting interrupt urb
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
PL-2303 ttyUSB0: pl2303_read_int_callback - length = 10, data = a1 20 00 00 00 00 02 00 02 00
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
PL-2303 ttyUSB0: pl2303_read_int_callback - length = 10, data = a1 20 00 00 00 00 02 00 83 00
drivers/usb/serial/pl2303.c: pl2303_close - port 0
drivers/usb/serial/pl2303.c: pl2303_close - shutting down urbs
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port 0
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - urb->status = -2
drivers/usb/serial/pl2303.c: pl2303_read_bulk_callback - port is closed, exiting.
drivers/usb/serial/pl2303.c: pl2303_read_int_callback (0)
drivers/usb/serial/pl2303.c: pl2303_read_int_callback - urb shutting down with status: -2
drivers/usb/serial/pl2303.c: set_control_lines - value = 0, retval = 0
usbcore: deregistering driver pl2303
drivers/usb/serial/pl2303.c: pl2303_shutdown