module loading order

module loading order

[Simon Leung]

Hi all,

This is a question that arose from a older kernel ( 2.6.21 ) but I think 
it's generic to all kernels. Actually this might not a question on the 
kernel itself at all. So here it goes,

I'm using a USB 3G modem with this kernel. The system loads three 
modules for it: pl2303, option and usbserial. Problem is, it looks like 
the order or loading is different ( I'm judging this by the order they 
appear in lsmod output):

Sometimes, lsmod says:
pl2303                 18628  0
option                  9664  0
usbserial              28296  2 pl2303,option

And sometimes, it says:
option                  9664  0
pl2303                 18628  0
usbserial              28296  2 option,pl2303

Problem is, if option is before pl2303, the device won't work properly. 
So my question is: who decides which is loaded first, or, why does lsmod 
give different order?

Thanks a lot!

module loading order

[Greg KH]

On Wed, May 11, 2011 at 09:00:30AM +0100, Simon Leung wrote:
> Hi all,
> 
> This is a question that arose from a older kernel ( 2.6.21 ) but I think 
> it's generic to all kernels. Actually this might not a question on the 
> kernel itself at all. So here it goes,
> 
> I'm using a USB 3G modem with this kernel. The system loads three 
> modules for it: pl2303, option and usbserial. Problem is, it looks like 
> the order or loading is different ( I'm judging this by the order they 
> appear in lsmod output):
> 
> Sometimes, lsmod says:
> pl2303                 18628  0
> option                  9664  0
> usbserial              28296  2 pl2303,option
> 
> And sometimes, it says:
> option                  9664  0
> pl2303                 18628  0
> usbserial              28296  2 option,pl2303
> 
> Problem is, if option is before pl2303, the device won't work properly. 
> So my question is: who decides which is loaded first, or, why does lsmod 
> give different order?

It's random and there is no way to specify the order unless you make one
module a dependancy of the other.

And for these modules, they should not be dependant on each other, so
you can't do that.

To fix this, you need to add a quirk to keep the option module from
binding to the device, please send the information to the
linux-usb at vger.kernel.org about this device and we will fix the drivers.

thanks,

greg k-h

module loading order

[Vikram Narayanan]

>> This is a question that arose from a older kernel ( 2.6.21 ) but I think
>> it's generic to all kernels. Actually this might not a question on the
>> kernel itself at all. So here it goes,
>>
>> I'm using a USB 3G modem with this kernel. The system loads three
>> modules for it: pl2303, option and usbserial. Problem is, it looks like
>> the order or loading is different ( I'm judging this by the order they
>> appear in lsmod output):
>>
>> Sometimes, lsmod says:
>> pl2303 ? ? ? ? ? ? ? ? 18628 ?0
>> option ? ? ? ? ? ? ? ? ?9664 ?0
>> usbserial ? ? ? ? ? ? ?28296 ?2 pl2303,option
>>
>> And sometimes, it says:
>> option ? ? ? ? ? ? ? ? ?9664 ?0
>> pl2303 ? ? ? ? ? ? ? ? 18628 ?0
>> usbserial ? ? ? ? ? ? ?28296 ?2 option,pl2303
>>
>> Problem is, if option is before pl2303, the device won't work properly.
>> So my question is: who decides which is loaded first, or, why does lsmod
>> give different order?
>
> It's random and there is no way to specify the order unless you make one
> module a dependancy of the other.
Isn't modules.dep file take care of this?

> And for these modules, they should not be dependant on each other, so
> you can't do that.
It does I guess. In my system, the modules.dep has,
kernel/drivers/usb/serial/pl2303.ko: kernel/drivers/usb/serial/usbserial.ko
Doesn't it mean that pl2303 is dependent on usbserial?

-
Thanks,
Vikram

module loading order

[Greg KH]

On Wed, May 11, 2011 at 09:38:28PM +0530, Vikram Narayanan wrote:
> >> This is a question that arose from a older kernel ( 2.6.21 ) but I think
> >> it's generic to all kernels. Actually this might not a question on the
> >> kernel itself at all. So here it goes,
> >>
> >> I'm using a USB 3G modem with this kernel. The system loads three
> >> modules for it: pl2303, option and usbserial. Problem is, it looks like
> >> the order or loading is different ( I'm judging this by the order they
> >> appear in lsmod output):
> >>
> >> Sometimes, lsmod says:
> >> pl2303 ? ? ? ? ? ? ? ? 18628 ?0
> >> option ? ? ? ? ? ? ? ? ?9664 ?0
> >> usbserial ? ? ? ? ? ? ?28296 ?2 pl2303,option
> >>
> >> And sometimes, it says:
> >> option ? ? ? ? ? ? ? ? ?9664 ?0
> >> pl2303 ? ? ? ? ? ? ? ? 18628 ?0
> >> usbserial ? ? ? ? ? ? ?28296 ?2 option,pl2303
> >>
> >> Problem is, if option is before pl2303, the device won't work properly.
> >> So my question is: who decides which is loaded first, or, why does lsmod
> >> give different order?
> >
> > It's random and there is no way to specify the order unless you make one
> > module a dependancy of the other.
> Isn't modules.dep file take care of this?

Yes, but again, there is no such dependancy between these two modules
as they are separate and do not control the same type of hardware.  Or
at least, they shouldn't.

> > And for these modules, they should not be dependant on each other, so
> > you can't do that.
> It does I guess. In my system, the modules.dep has,
> kernel/drivers/usb/serial/pl2303.ko: kernel/drivers/usb/serial/usbserial.ko
> Doesn't it mean that pl2303 is dependent on usbserial?

Yes, and so is the option module.  But you are looking at a wierd device
that somehow thinks it is both an option device, and a pl2303 device,
which are totally different chipsets.

thanks,

greg k-h

module loading order

[Simon Leung]

> Yes, and so is the option module.  But you are looking at a wierd device
> that somehow thinks it is both an option device, and a pl2303 device,
> which are totally different chipsets.
>
> thanks,
>
> greg k-h
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

If I understand modules.dep correctly, it says that both pl2303 depend 
on usbserial.
So when either is loaded, usbserial will be loaded. But the problem here 
is that pl2303
should not be loaded at all as it's for USB-serial adapter, not 3G 
modem. I'm not sure
what controls that.

Thanks,


Simon

module loading order

[Greg KH]

On Wed, May 11, 2011 at 10:24:28PM +0100, Simon Leung wrote:
> 
> > Yes, and so is the option module.  But you are looking at a wierd device
> > that somehow thinks it is both an option device, and a pl2303 device,
> > which are totally different chipsets.
> 
> If I understand modules.dep correctly, it says that both pl2303 depend 
> on usbserial.

You mean "both pl2303 and option", then yes.

> So when either is loaded, usbserial will be loaded.

Yes.

> But the problem here is that pl2303 should not be loaded at all as
> it's for USB-serial adapter, not 3G modem. I'm not sure what controls
> that.

The descriptors of the device itself.

What does 'lsusb' show with this device plugged in?

And what kernel version are you using here?

thanks,

greg k-h

module loading order

[Simon Leung]

>> But the problem here is that pl2303 should not be loaded at all as
>> it's for USB-serial adapter, not 3G modem. I'm not sure what controls
>> that.
> The descriptors of the device itself.
>
> What does 'lsusb' show with this device plugged in?
> And what kernel version are you using here?
>
I'm using 2.6.21 on an ARM board. lsusb says:
|12d1:1446
after usb_modeswitch:
||12d1:1001
|

module loading order

[Greg KH]

On Thu, May 12, 2011 at 09:33:32AM +0100, Simon Leung wrote:
> 
> >> But the problem here is that pl2303 should not be loaded at all as
> >> it's for USB-serial adapter, not 3G modem. I'm not sure what controls
> >> that.
> > The descriptors of the device itself.
> >
> > What does 'lsusb' show with this device plugged in?
> > And what kernel version are you using here?
> >
> I'm using 2.6.21 on an ARM board. lsusb says:
> |12d1:1446
> after usb_modeswitch:
> ||12d1:1001

2.6.21 is _very_ old and unsupported, please use a modern kernel if you
need to ask the community for help.  If you are stuck with this version
for some reason, please contact the vendor that is providing you support
for this as you are paying them for this.

If you can reproduce this with the 2.6.38 kernel release, or newer, I'll
be glad to help you out.

thanks,

greg k-h

module loading order

[Simon Leung]

> 2.6.21 is _very_ old and unsupported, please use a modern kernel if you
> need to ask the community for help.  If you are stuck with this version
> for some reason, please contact the vendor that is providing you support
> for this as you are paying them for this.
>
> If you can reproduce this with the 2.6.38 kernel release, or newer, I'll
> be glad to help you out.
>
> thanks,
>
> greg k-h

Thanks. I know it's very old and not supported here. But I was hoping 
it'd be something simple
  outside of the kernel space, e.g. udev configuration. Anyway, I have a 
pretty dumb work around:
remove the ps2030.ko file. :)

Thanks again.