Fedora 9 (and older versions) do not include the snd-serial-u16550 module (CONFIG_SND_SERIAL_U16550). Could you please add this in future kernel versions? The driver compiles without any problems and takes less than 20 KiB, so I don't see why it is not included.
FYI: I know it's theoretically possible to compile this by myself, but compiling the _entire_ kernel and module set is out of the question since that would take ages, and compiling just the module I need seems impossible. Even when using a kernel tree prepared using rpmbuild, the vermagic string doesn't match what Fedora uses. Anyway, I just mentioned this so that I won't be dismissed by a simple "compile it yourself". :-) Every single working module that is safe (non-experiemental) and is not obsoleted by another module that replaces it should IMO be included with the distro.
There is one caveat with this option.. This driver accesses the serial port hardware directly, so make sure that the standard serial driver isn't used or deactivated with setserial before loading this driver. But asides from that, I don't see any real reason to prevent us turning this on.
Thanks for responding to this bug. Regarding your caveats, I don't see how anyone except snd-serial-u16550 users would be affected, and I'm sure I speak for them (if there are more than one of us :-)) when I say that I _greatly_ prefer adding a line in some config file to disable the standard serial driver to spending over 1 hour recompiling the kernel to get the module I need. :-)
Just to verify that it would work, I downloaded the srpm of the latest kernel (2.6.25.3-18.fc9), set CONFIG_SND_SERIAL_U16550=m in config-generic, and rebuilt the entire thing with rpmbuild -bp. After doing "setserial /dev/ttyS0 uart none", I could load snd-serial-u16550, and it's working perfectly. This does not mean I withdraw my bug report: It took 1 hour and 15 minutes to rebuild the kernel on my dual core Athlon64 X2 3800+, and I would _really_ like to avoid doing that every time there's a kernel update. ;-)
Enabled in 2.6.25.4-22
kernel-2.6.25.4-30.fc9 has been submitted as an update for Fedora 9
kernel-2.6.25.4-30.fc9 has been pushed to the Fedora 9 testing repository. If problems still persist, please make note of it in this bug report. If you want to test the update, you can install it with su -c 'yum --enablerepo=updates-testing update kernel'. You can provide feedback for this update here: http://admin.fedoraproject.org/updates/F9/FEDORA-2008-4630
As expected, the snd-serial-u16550 module works perfectly in kernel kernel-2.6.25.4-30.fc9. Thank you for including it! :-)
kernel-2.6.25.4-30.fc9 has been pushed to the Fedora 9 stable repository. If problems still persist, please make note of it in this bug report.