Re: driver migration

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On Fri, Feb 19, 2016 at 08:55:33PM +0000, tilman wrote:
> Greg KH <gregkh@...> writes:
> 
> > 
> > On Fri, Feb 19, 2016 at 06:49:50AM +0000, tilman wrote:
> > > Hello
> > > 
> > > I configured and setup a more recent kernel:  V4.5.0-rc4
> > > 
> > > The driver compiles and inserts.
> > 
> > What driver?  You have provided no context here :(
> My apologies -- what I meant to say was: I inserted the compile usbrsa
> driver. The code of the driver I posted on Feb 16th.
> 
> > 
> > > When I plugin the USB-Dongle, the machine
> > > freezes (not sure whether it freezes during the firmware download or after
> > > it once it has reenumerated). 
> > 
> > Your kernel logs should show you this.
> 
> The kernel freezes before it can log the kernel oops:
> 
> Feb 19 07:26:35 btron kernel: [  241.247360] usbcore: registered new interface d
> river usbrsa
> Feb 19 07:26:35 btron kernel: [  241.247388] usbserial: USB Serial support regis
> tered for IO-DATA - USB-RSA - (prerenumeration)
> Feb 19 07:26:35 btron kernel: [  241.247412] usbserial: USB Serial support regis
> tered for IO-DATA - USB-RSA
> 
> ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
> ....
> 
> > The kernel logs can provide you with a full traceback, we can't do much
> > without that.
> I understand that and I would love to provide one -- there is however no
> traceback logged. All I have is a kernel message on the console:
> 
> BUG: unable to handle kernel paging request at ...
> 
> When I had the driver running on the kernel version 3.13.0, things started
> to go wrong in usbrsa_attach of the usbrsa driver (see first posting on Feb
> 16th)
> 
> I will comment out all functional parts of the driver, and check if it still
> fails. If it no longer crashes, I will comment in procedure by procedure
> until it crashes hoping that I can isolate the problem that way ... 
> If there are better/faster debugging techniques I would love to learn about
> them :-)

You can use ftrace to help you watch the flow of your driver before it
crashes, or just printk, as you have found out, is the best way to debug
things.

best of luck,

greg k-h
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