libftdi Archives

Subject: Re: Claiming devices has no effect under Linux

From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Tue, 5 Oct 2010 19:24:42 +0200
>>>>> "Thomas" == Thomas Klose <thomas.klose@xxxxxxxxxxxxx> writes:

    Thomas> Am Dienstag, den 05.10.2010, 18:14 +0200 schrieb Uwe Bonnes:
    >> >>>>> "Uwe" == Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
    >> writes:
    >> >>>>> "Thomas" == Thomas Klose <thomas.klose@xxxxxxxxxxxxx> writes:
    Uwe> In your situation, however it is wrong. Ideas how to handle that
    Uwe> situation are welcome.
    >>  To clarify the situation.  Device gets plugged, ftdi_sio gets
    >> loaded.  First libftdi open calls libusb_detach_kernel_driver() and
    >> gets access.  Second libftdi open calls calls again
    >> libusb_detach_kernel_driver() and gets access too.

    Thomas> To be honest, I think tampering with the system's configuration
    Thomas> by detaching device drivers seems a little drastic to me,
    Thomas> especially if it is default behavior.

    Thomas> sio gets loaded because it is the driver for devices with a
    Thomas> certain vendor and product id. If this is not wanted for a
    Thomas> device, it should be set to another id.

But here you get in a chicken/egg problem. VID 0x403/PID 0x6001|6010 are the
default FTDI VID/PID and ftdi_sio needs to be loaded for many devices on the
market. However 0x403/PID 0x6001|6010 is also the default VID/PID of new
FTDI devices you want to use for something else. So how do you program
these to a diffent VID/PID?

With the ability to specify VID/PID/Product description and Serial string in
libftdi, you also minimize the changes to "catch" a wrong device. 


Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

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