Is there some implicit locking of device methods?

Bartosz Fabianowski freebsd at
Tue Apr 26 12:39:22 UTC 2011

> You need to handle all cases in your driver. Fortunately there exists a
> solution for this already, called USB cdev. See

I went through all the USB drivers with a fine comb (the driver I am 
porting was based on the old USB stack and so I needed to adjust it for 
the new stack). Drivers like ulpt seem to be based around usb_fifo_* 
structures. If I understand usb_fifo_* right, it gives you a single 
device with FIFO semantics. This is not sufficient in my case. My device 
is opened for reading by several processes in parallel and needs to keep 
a separate FIFO per process. I implemented this via device cloning - and 
I could not see how to integrate that with usb_fifo_*. Thus, I based my 
driver on the raw cdev framework. Am I missing something obvious and 
making my life unnecessarily hard?

- Bartosz

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