Re: 2.4.30 - USB serial problem

[Ian Leonard <ian@smallworld.cx>]

Ian Leonard wrote:
> Pete Zaitcev wrote:
> 
>> On Thu, 26 May 2005 18:52:10 +0100, Ian Leonard <ian@smallworld.cx> 
>> wrote:
>>
>>
>>> We recently upgraded from 2.4.24 to 2.4.28 and the problem described 
>>> below appeared. I have tested it on 2.4.30 and the fault still exists.
>>> [...]
>>> Examining the packet that caused the problem showed it was very 
>>> similar to the others but it contained 0x0a. This obviously stuck out 
>>> as being a candidate for some sort of translation problem.
>>
>>
>>
>> The above looks almost too obvious but for this:
>>
>>
>>> I also built a 2.4.28 kernel with the ftdi_sio and usbserial code 
>>> from the 2.4.24 release. It also failed. This was a surprise and I am 
>>> wondering of I did it correctly.
>>
>>
>>
>> Did you nail down a scenario which we can debug? Frankly it's not 
>> credible
> 
> 
> Not as yet. As I indicated I can only test the problem at a remote site 
> and I don't get much time to look at it.
> 
>> that transplanted usbserial and ftsi_sio would fail to work. I know that
> 
> 
> I agree, it can't be the case. To prove that I hadn't just made a 
> mistake, I transplanted the whole usb branch and it still failed. This 
> really points to the user app - which is complex and I haven't got to 
> the bottom of it. It's a multi-threaded library and I see it's doing 
> some sort of packet requeuing based on a timer. I can't see what has 
> changed but I am guessing it's a kernel timing issue. It would explain 
> everything.
> 
>> I changed quite a bit between 2.4.24 and 2.4.28, but your experiment
>> undoes that.
> 
> 
> I think the usb is red herring - sorry about that. BTW, I see you have 
> cc'd Ian (hi Ian). By coincidence we are using an MEV usb device.

I finally got to the bottom of this problem (with Ian Abbotts help). I 
had the wrong usb host module loaded, ubci not usb_uhci (in fact it was 
compiled in to the kernel). The write call to the usbserial device was 
blocking. This seemed to happen when a data packet of more than 8 bytes 
was written.

Having two drivers, one which works sometimes seems to be a bit of an 
elephant trap.

This was an error that occurred when I was preparing the new config 
file. I would guess I left the usb as the default. It might me better to 
have no defaults in the config, that way you are forced to make the 
correct selection.

What is the recommended way of transferring .config files between kernel 
versions? I see there are always a lot of changes. Can you safely just 
copy the existing file and then run xconfig to include any new options?


-- 
Ian Leonard

Please ignore spelling and punctuation - I did.