On Wed, May 05, 1999 at 10:23:29AM -0600, Jake Griesbach wrote: > I'm running the most recent kernel (2.2.7), and I also use a Crystal > semiconductor sound card, so I have the cs4232 kernel module. Sometimes I > get the kernel error: > > kernel: Sound error: Couldn't allocate DMA buffer > > I have plenty of available memory left, so I don't understand why I am > getting this error. Has anybody else received this error? Does anybody > know of a workaround or fix for it? I haven't received this error before > installing the 2.2.7 kernel.
linux/Documentation/sound/README.modules The sound modules normally allocate DMA buffers during open() and deallocate them during close(). Linux can often have problems allocating DMA buffers for ISA cards on machines with more than 16MB RAM. This is because ISA DMA buffers must exist below the 16MB boundry and it is quite possible that we can't find a large enough free block in this region after the machine has been running for any amount of time. The way to avoid this problem is to allocate the DMA buffers during module load and deallocate them when the module is unloaded. For this to be effective we need to load the sound modules right after the kernel boots, either manually or by an init script, and keep them around until we shut down. This is a little wasteful of RAM, but it guarantees that sound always works. To make the sound driver use persistent DMA buffers we need to pass the sound.o module a "dmabuf=1" command-line argument. This is normally done in /etc/conf.modules (or the more proper /etc/modules.conf) like so: options sound dmabuf=1 If you have 16MB or less RAM or a PCI sound card, this is wasteful and unnecessary. It is possible that machine with 16MB or less RAM will find this option useful, but if your machine is so memory-starved that it cannot find a 64K block free, you will be wasting even more RAM by keeping the sound modules loaded and the DMA buffers allocated when they are not needed. The proper solution is to upgrade your RAM. But you do also have this improper solution as well. Use it wisely. Documentation is nifty. -- Ian Peters "I never let schooling interfere with my education." [EMAIL PROTECTED] -- Mark Twain
