Re: CMD part of a driver: questions

On 12/08/2007 22:33, Askar Ibragimov wrote:
> Hello,
> 
> I am writing the new driver for Advantech PCI1751 and need to
> implement CMD interface support. I already got INSN part of the driver
> ready, but now I need a contionious infinite acquisition. Can anyone
> please help answering the following questions:
> 
> - what is the purpose of the procedure declared in the "do_cmd" field
> of the comedi_subdevice record? I checked as an example das16m1.c of
> COMEDI distribution and the routine just doing some setup. I need to
> perform "acquisitions" on counter chip, so what I can write in this
> routine? Just start counter? :)

"do_cmdtest" tests the command to make sure the driver and hardware can 
support it.  "do_cmd" sets up the hardware to perform the command 
asynchronously.  For most hardware this involves setting registers to 
configure modes, and/or enabling DMA channels and enabling interrupts.

> - There is no indication of any activity of reading something in
> do_cmd procedures that I saw in various drivers. Am I right that
> COMEDI uses insn interface reading routines to handle CMD
> acquisitions?

For most drivers, the data transfer occurs in the interrupt handler, 
though it may share some routines with the insn interface.

-- 
-=( Ian Abbott _at_ MEV Ltd.    E-mail: <abbotti_at_mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-

Received on 2007-08-14Z08:56:17