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From: John Baldwin <jhb@freebsd.org>
To: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Cc: freebsd-current@freebsd.org, ken@freebsd.org, scsi@freebsd.org
Subject: Re: Panic on reloading a driver with same DEVICE_PROBE() return value
Date: Tue, 09 Feb 2016 14:00:12 -0800
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On Tuesday, February 09, 2016 05:45:38 PM Sreekanth Reddy wrote:
> Hi,
> 
> While debugging more, I got one more clue,
> 
> -----------------------------------------------------------------------------------------------
> static driver_t mps_pci_driver = {
>         "mpr",
>         mps_methods,
>         sizeof(struct mps_softc)
> };
> 
> static devclass_t       mps_devclass;
> DRIVER_MODULE(mpr, pci, mps_pci_driver, mps_devclass, 0, 0);
> -------------------------------------------------------------------------------------------------
> 
> in the above code snip-set, if I changed "DRIVER_MODULE" line as
> DRIVER_MODULE(mpr3, pci, mps_pci_driver, mps_devclass, 0, 0);
> (i.e. from "mpr"  to "mpr3") then I am not observing any panic and I
> can load & unload the mpr driver multiple times.

Oh, that might be required, yes.  DRIVER_MODULE uses its arguments to define
a module name (in this case as "pci/mpr") and module names are required to
be unique.  I believe you should be getting a printf warning about this on
the console.  Something like:

"module_register: cannot register pci/mpr from blah.ko; already loaded from foo.ko"

-- 
John Baldwin