Re: [TiLP-devel] Silver kernel module (Linux) : ok !

[Tijl C. <ti...@ul...>]

On Thu, 15 Apr 2004 11:12:57 +0200 (CEST), Romain Li=E9vin wrote:

> Hi Tijl,
>=20
>> On Tue, 13 Apr 2004 23:04:51 +0200 (CEST), Romain Li=E9vin wrote:
>>
>>> Note: kernel module behaviour/implementation is the same as the
>>> lib-usb one but is working better (no transfer interruption).
>>> Kernel module should have less latency (by nature).
>>>
>>> Tijl: I think that a FreeBSD kernel module will be the only way
>>> to make it work on BSD.
>>
>> The cable works fine using libusb (there are no transfer
>> interruptions like you mentioned above), except with ohci, where
>> the cable doesn't get probed and attached so a kernel module
>> wouldn't work here either.
>=20
> I did'nt know. But, I noticed in libticables support that you don't
> reset endpoints (due to a lack of support in libusb/BSD). This is
> important to make sure that a transfer is starting on a known state
> (and this is Ti-Connect do).

I suspect the reason it isn't implemented in libusb/bsd is because
there aren't any ioctl calls in ugen to clear a halt or reset the
endpoints.
I'm not entirely sure, but I think this is handled by the ugen driver
itself.

This is the relevant code snippet from the ugen interrupt handler.
'status' holds the transfer exit status.

  if (status =3D=3D USBD_CANCELLED)
    return;

  if (status !=3D USBD_NORMAL_COMPLETION) {
    DPRINTF(("ugenintr: status=3D%d\n", status));
    if (status =3D=3D USBD_STALLED)
      usbd_clear_endpoint_stall_async(sce->pipeh);
    return;
  }

> I can say that receiving a FLASH app or doing a ROMdump w/ libusb
> support under Linux (can) fails at any moment.

Well, I must admit that I haven't done any extensive testing but so
far I haven't had any problems with the cable.

> Well, there is a good reason to keep this support ;-)

You can always make it platform specific and have the linux version
use a kernel module, but I'd keep the libusb code in the bsd port, in
case somebody decides to make a NetBSD/OpenBSD/... port. The libusb
method is more portable.