From the ALSA wiki
|The FAQs have been reorganized. The new location of this question is FAQ#How can I update the ALSA version when running a 2.6.x kernel?|
How do I update the ALSA version when running a Linux 2.6.x kernel?
If there's a newer kernel version available, it's likely the included ALSA drivers have been updated too. You may find it easier just to download the newer kernel rather than trying to update the ALSA parts inside your existing kernel source code.
If you want to update the ALSA version included with your current kernel, check the AlsaBuild2.6 page.