[alsa-devel] [RFC][PATCH 0/3] ALSA: fireface: new driver for RME Fireface series (MIDI only)

[Takashi Sakamoto]

On Dec 07 2015 10:52, Takashi Sakamoto wrote:
> Hi,
>
> On Dec 07 2015 10:37, Jonathan Woithe wrote:
>> On Mon, Dec 07, 2015 at 10:27:08AM +0900, Takashi Sakamoto wrote:
>>> On Dec 07 2015 06:57, Jonathan Woithe wrote:
>>>> On Sun, Dec 06, 2015 at 10:23:41PM +0900, Takashi Sakamoto wrote:
>>>>> Unfortunately, ffado library can disturb this functionality.
>>>>> In RME::Device::init_hardware() function, the library sends a write
>>>>> transaction
>>>>> to 0x0000801003f4 with invalid value as higher part of address in
>>>>> IEEE 1212 or
>>>>> ISO/IEC 13213. This is a worst case I describe in patch 03.
>>>>
>>>> The number which FFADO writes to this register is not invalid: it is
>>>> in fact
>>>> the same number which is used in drivers on other operating systems
>>>> (obtained from protocol analysis).
>>>
>>> No.
>>>
>>> As long as I tested with a debug option to firewire-ohci module, it
>>> sends
>>> write transaction with '01000000'. This value includes invalid node ID.
>>
>> Curious.  Fair enough (although I was confused by the reference to the
>> "higher part" in the commit message: it implied the higher part of the
>> address in my mind, but in fact the issue with the node ID relates to the
>> lower part.  Whatever.  I'll look into it at some point.
>
> In IEEE 1212 (or ISO/IEC 13213), 64 bit addressing is defined. IEEE 1394
> utilize the specification.
>
> Here is a actual example of the 64 bit address:
>   * FFC1'FFFF'F000'0904 (oPCR[0] in node FFC1)
>   * FFC2'FFFE'0000'0000 (the first address of Private space in node FFC2)
>   * FFC3'ECC0'8000'0000 (the address of Echo Fireworks Command in node
> FFC3)
>
> I mean the 'higher part' is 4 byte in MSB of the address. Drivers
> register the 4 byte to 0x'0000'8010'03f4, then Fireface 400 transfers
> asynchronous transactions to an address including the 4 byte in its MSB.

More explaination.

If OHCI 1394 host controller gets node ID of FFC7 on the IEEE 1394 bus 
and ALSA Fireface driver allocates local address of 0x'4567'0000'0000 of 
the controller, then the driver must register the value of '0xFFC74567' 
to Fireface 400.

Actually, for Fireface 400, the value should be aligned to little 
endiann. Therefore, the driver sends write transaction with value of 
'0x6745C7FF'.

In my understanding, 0x0000 for node ID is invalid. Furthermore, 0x0010 
is not always true because the address range which drivers allocate on 
the controller is different depending on situation.


Regards

Takashi Sakamoto