Re: USB drivers

Bernd Walter wrote:

>On Wed, Aug 04, 2004 at 10:41:50AM -0400, Chris wrote:
>  
>
>>The last time I programed was over 15 years ago and I was thinking of 
>>looking into the USB drivers for FreeBSD concerning multifunction 
>>devices. If I ask stupid questions forgive me because I am seeing this 
>>as a user.
>>
>>First I would like to know if there is a technical reason why two 
>>different divers cannot attach to the same device. If each driver works 
>>well independently, what is the reason to prevent the second one from 
>>attaching? I would assume that if you attempted to use both drivers at 
>>the same time you would get a device busy error.
>>    
>>
>
>USB devices can be designed to have multiple interfaces at which you
>can have different drivers - e.g. you can have a ulpt/umass combo
>and both drivers just clain the according interface from the same
>device.
>Therefor also drivers can be programmed for whole USB devices and for
>USB subdevices.
>This works perfectly with FreeBSD.
>
>  
>
>>Am I misunderstanding something here? I see ulpt: and unlpt: attaching 
>>to the same device and the choice of which one to use is up to the user 
>>and the hardware they have. If we have two drivers attach in one case 
>>why, and where, do we prevent other drivers from attaching if they meet 
>>the minimum requirements?
>>    
>>
>
>unlpt and ulpt are just different representations from the same driver.
>There is absolutely no sense in having two clients printing at the same
>time on the same printer, so blocking each other is absolutely reasonable.
>Scheduling multiple requests is up to software like lpd.
>See ulpt(4) for details about the functional difference in ulpt vs. unlpt
>device nodes - depending on the printer you will likely end up in always
>using the same devicenode.
>Why do you think this is wrong?
>  
>

What I am looking to accomplish is to attach uscanner and ulpt to an 
EPSON CX5400. While each driver works great by itself I am unable to 
attach both at the same time. I was told on this list that we may not 
attach two drivers to the same device. If this is not correct then I 
would appreciate a little help in attaching existing drivers or writing 
a new one.

Chris