libftdi Archives

Subject: Re: Claiming devices has no effect under Linux

From: Thomas Klose <thomas.klose@xxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Wed, 06 Oct 2010 22:21:57 +0200
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.

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

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