On 04/20/2012 09:41 AM, Fry, Donald H wrote:
Today we have wifi devices with stuff implemented in hardware and other things
done in microcode. For example the 6205 device. Today we do modprobe iwlwifi
to install and modprobe iwlwifi -r to remove the module.
'Tomorrow' we use the same hardware but with a different microcode file which
changes the driver quite a bit. The PCI device/vendor id's are the same since
the hardware has not changed, however the kernel driver is new.
We would like to shield the users from having to know the details of our driver
and make things look pretty much like they do today. What we have been
testing, and have done a lot of code refactoring to clean the driver up in
preparation for this change is the following:
The base/core/common functionality is still called iwlwifi which interacts with
the hardware. On modprobe, the driver tries to find a microcode file to run
based on the device/vendor id/sub-id. While parsing the microcode file, it
will indicate which software API it supports, which will indicate which
specific module to use, module A (old) or module B (new). This way the user
still uses modprobe iwlwifi to install, and iwlwifi will request the
appropriate specific module to make the hardware function.
However, since module A (for example) requires iwlwifi, an attempt to modprobe
iwlwifi -r results in a message that iwlwifi is still in use. Module A must be
removed first followed by iwlwifi, etc. While this may be obvious from looking
at lsmod for a kernel developer, it is not obvious for most users. While
trying to provide a user friendly way to accomplish this, I found the .conf
files described in /etc/modprobe.d. This is one way to hide the details of
what we are doing, and allow most users to continue to install with modprobe
iwlwifi and remove with modprobe iwlwifi -r.
If there is a better way to do this, I am very open to suggestions. If this is
an acceptable solution, how do we get the iwlwifi.conf file out to the distros
and user community before or at the same time as this new change so we do not
break things?
How large are these two modules? With debugging disabled, iwlwifi is less than
250K, which is not that large. Perhaps you could load both, or build both into a
monolithic iwlwifi. The appropriate calls can be setup after the fw is read. Any
globals in the two routines need to be unique anyway, otherwise the build will
fail when iwlwifi is built in and not compiled as a module.
Larry
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