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Entry  23 Aug 2005, Konstantin Olchanski, Info, new mvmestd api 
    Reply  01 Sep 2005, Stefan Ritt, Info, new mvmestd api 
       Reply  01 Sep 2005, Stefan Ritt, Suggestion, new mvmestd api 
       Reply  10 Sep 2005, Konstantin Olchanski, Info, new mvmestd api 
          Reply  11 Sep 2005, Stefan Ritt, Info, new mvmestd api 
             Reply  02 Nov 2005, I. K. arapkorir, Info, new mvmestd api 
                Reply  02 Nov 2005, Pierre-Andre Amaudruz, Info, new mvmestd api 
Message ID: 222     Entry time: 10 Sep 2005     In reply to: 220     Reply to this: 223
Author: Konstantin Olchanski 
Topic: Info 
Subject: new mvmestd api 
> Good that you brought up the MIDAS VME API again, since this is still not complete, but
> has to be completed soon.

Right, but I can only complete the parts that I thought of and for which I already have
code. This leaves out support for DMA (read: any block transfers) and interrupts.

> Let me summarize the goals:
> - have a single set of functions which can be used with all VME CPUs/Interfaces at our
> institutes. Using this technique, one can change the interface or CPU and still keep
> the same frontend source code. This was already successfully done with the MIDAS CAMAC
> standard (as defined in mcstd.h)

Well, all interfaces are different and no amount of software will make them look all the
same. I am now facing this problem with the Wiener CCUSB CAMAC-USB2 interface. I can
implement all of mcstd.h, but the interface is intended to be used by downloading it with a
CAMAC readout program and mcstd.h knows nothing about that.

> - base any ADC/TDC driver we write on that API, so these modules can be used with any
> CPU/Interface without changing the driver

Right. Most useful.

> - have a simple and easy to understand set of functions


> - "cover" any specialities from the drivers, like memory mapping.

Exactly. We are facing a tricky task of inventing one API for two completely different
modes of operation- purely memory mapped access on UniverseII based hardware and message
passing access for the SIS3100 and VMUSB (Wiener VME-USB2).

> So one should only use explicity vme_read/vme_write functions.

Rightey-ho. The fly in the ointement is that all VME ADC and TDC drivers in TRIUMF are
written assuming memory mapped access, and I will not convert them to vme_read/vme_write
overnight (think of testing).

> So I would propose the following:
>   mvme_set_crate()   each funciton has a _get_ partner, like mvme_get_crate()
>   mvme_set_address_mode()
>   mvme_set_amod()
>   mvme_set_blocktransfer()
>   mvme_set_fifomode()             // speciality of the SIS3100 interface, write a
>                                   // block of data to the same address
>   ...
>   mvme_read(vme_address, dest_addr, num_bytes);
>   mvme_write(src_addr, vme_address, num_bytes);

This is compatible with what we do now and I will look into implementing this for
VMIC/Linux and MVME/VxWorks interfaces.

> Now I would like to hear anybody's comments. If we agree on this method, we have to
> define a complete set of functions mvme_set_xxx.

We currently require only single-word transfers so we can concentrate on mvme_set_xxx for
block-transfers later.

> If we get a new interface in the
> future which has new functionality (like 2eVME block transfers), we have to change the
> API each time (while with the ioctl() we only would have to add one parameter).

This amounts to the same thing: add a new function or add a new ioctl() call.

> maybe we can make a more generic mvme_set_vme_mode(mode), where mode could be fifomode,
> 2eVME mode, chained block transfer mode and so on.

This is a can of worms and I would rather postpone discussion of block transfers. To give
you a taste: UniverseII does not have a "fifo mode"- it *always* increments the vme address
 (silly). A fifo mode can be emulated using chained transfers (read 256 bytes from
addresses A through A+256, then read 256 more from address A, etc.), but the present VMIC
VME library does not support chained transfers. On VxWorks, we do not even have a driver
for the DMA engine, so not block transfers there at all.

I will now think about and post an updated proposal for mvmestd.h


P.S. There is a proposal for musbstd.h heading your way, too.
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