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 12:09:29 +0200
Am Mittwoch, den 06.10.2010, 17:22 +0800 schrieb Xiaofan Chen: 
> > 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.
> This is actually not true. Just a simple example, if you do not have
> Windows, and want to change the EEPROM configuration of the
> FTDI device. Then you can use Uwe's application which is based
> on libftdi. So you will need to detach the exisiting kernel driver to do
> it. So give the user the freedom to either use the kernel driver or
> use libftdi is very good.
This freedom was never in endangered.

> There are often cases that the kernel driver may not be the best
> to be used.
> The Linux capability of being able to attach/detach a kernel
> driver is really a blessing, if you ask the libusb users.
> > If for some reason the user explicitly does not want the system to load
> > a certain module, he can create an blacklist entry in /etc/modprobe.d
> This is one way, but not the only way. Last time it might be the only
> way, now it is not.

That is not the question. The real issue is: Should a library like
libftdi by default tamper with the system's global configuration?

In my opinion this is just not what it is expected to do! In this way I
could write a X application which changes the desktop background every
time it starts for a better user experience and leaves this way because
the user will like it better. This also would be a great new way to
change the desktop background...

> Another example is libhid for HID device. You can detach the
> kernel HID driver to use libhid. There are many generic HID device
> out there yet the kernel HID driver is not so good. So one way is
> to blacklist the device, the other way is to detach the kernel HID
> driver.
> > This is the Linux way to do those things.
> Your way is one way to do things. Again, the ability to detach the kernel
> driver by program is a blessing for Linux if you ask the libusb users.
> Unfortunately it is not as easy under Windows and Mac OS X.
Again: This is not the question.

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