libftdi Archives

Subject: Re: Claiming devices has no effect under Linux

From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Wed, 6 Oct 2010 22:27:45 +0200
>>>>> "Thomas" == Thomas Klose <thomas.klose@xxxxxxxxxxxxx> writes:

    Thomas> Am Mittwoch, den 06.10.2010, 15:39 -0400 schrieb DJ Delorie:
    >> > If the device has a VID/PID which is associated with a kernel
    >> module I > would expect that module to be loaded. If a device is not
    >> intended to be > used with sio it *must* use another VID/PID. This is
    >> the whole idea > behind the VID/PID system.
    >> What about a device which *is* intended to be used by sio, but
    >> *sometimes* you want to bit-bang it instead?
    >> In my case, I use the FT232R chips as usb-to-serial ports for my
    >> MCUs, but to *program* the MCU, I have to fiddle with the cbus pins
    >> too.  For that task, I need to load libftdi.  For normal
    >> communications I just use /dev/ttyUSB* via sio.

    Thomas> I do not see the problem. In this case you could detach sio with
    Thomas> modprobe, rmmod, usb_detach_kernel_driver(), or whatever in your
    Thomas> *application*. I am just saying, detaching driver modules as
    Thomas> default behavior of a *library* seems surprising to me, because
    Thomas> it generalizes this not very beautiful, yet necessary and valid
    Thomas> approach.

But rmmod requires being root, while our concept only requires access to the

Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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