Built-in modules review

Andy Whitcroft apw at canonical.com
Tue Mar 16 15:08:38 UTC 2010

During the karmic cycle we built-in a number of modules.  Some as part
of the removal of udev random module loading, and some as a part of
trying to speed up the boot.  At that time modprobe was significantly
slower than it is now and it is appropriate to review that decision.

We have also had a number of problems reported wherein people can no
longer parameterise their modules as they wish and/or replace them
easily to test updated features.  In one specific case the wrong PATA
driver is binding to the device and as it is built-in there is no longer
a remedy.

I have prepared a summary of the sub-systems and drivers as built-in
currently and added them to the blueprint kernel-lucid-config-review's
spec, at the URL below:


Filesystems: we currently have all of the ext2,3,4 filesystems builtin,
plus all of the diagnostics filesystems (procfs et al), and also fuse.
Other than FUSE these are all boot essential.  I believe FUSE is
required for automounting which needs confirmation.  No changes

Subsystems: of those listed the only one which appears to be a
candidate for modularising is netfilter, I cannot recall this being
required builtin.

Network Protocols: again these seem reasonable, the only candidates for
review being DCB and XFRM, if anyone can confirm that we need those.

ATA Drivers: we have the majority of the PATA and SATA drivers built in.
We already have reported issues with the PATA drivers where blacklisting
could be used as a work around if they were not built in.  We are also
exposing users to some level of risk including all these drivers which
are not used.  In testing on the reference platform I did see a minor
but measurable performance hit to modularising the SATA driver there.
As we are moving to SATA over time I would propose we pull out all of
the PATA drivers and build in only the 2 or 3 most common SATA drivers.

Input drivers: here most things are modules already.  TOUCHSCREEN and
TABLET are possible candidates for modularising.

HID drivers: we already took action to move HID to modules and most of
the actual drivers already appear to be modules.  No changes required.

If people are in agreement I will put together a patch set to make these



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