iso support

[Stanislaw Gruszka]

Hi Matthieu
On Thursday 17 of November 2005 19:23, matthieu castet wrote:
> > I tried to take more deeply look at urb->status in iso mode. 
> > Of course I was wrong telling urb->status is equal -EILSEQ  
> > allways, it's only quite frequency situation on uhci host controller
> > (which I have on my machine). After my investigation on uhci driver code, 
> > seems urb->status is equal last non zero iso_frame_desc[i].status or zero. 
> > Eg: if all frames are ok there usb->status is 0. In iso mode if reserved bandwitch 
> > is greater then real bandwitch, there are incoming frames without any data 
> > and such with EILSEQ error. This is the reason why on uhci there 
> > are lot of urb->status == -EILSEQ.
> Have you try with other alternative where that have a smaller packet 
> size in order if it change something ?
I tried all alternate setting for input interface but whitout any influence on 
error frequency, maybe speed of my internet connection is to small to see
any difference.
> My conclusion was there was something strange on the eagle usb iso 
> management : for me there are lot's of -EILSEQ errors when the modem do 
> nothing and no error when I download at full rate.
It's prove theory uhci with uealge-atm returns EILSEQ error when 
empty frames comm in. More empty frames - more EILSEQ errors.

> Alan Stern also think it could be a bug in the modem [1].
Now I think so too, but I think also uhci should not write error
to urb->status on isoc urb as do ohci driver (AFAIK). If all frames 
except one are ok then we have error on "whole" urb. Anyway 
in my opinion on iso pipe urb->status value should be ignored

> Have you try with other iso device (webcam, ...) ?
> I don't have any here, so I ccouldn't try it.
No I have no other usb devices. 

__
Regards 
Staszek

> 
> Matthieu
> 
> 
> 
> [1]
> I don't think it's a problem with the UHCI driver.  It could be a problem
> with the modem or the host controller.
> 
> The UHCI driver returns -EILSEQ as status when no data at all is received
> from the device.  Even an "empty" packet actually contains some data: a
> DATA0 PID and a 16-bit CRC.  It's possible that the modem, instead of
> sending this data to indicate an empty packet, is sending nothing.
> 
> Alan Stern