Description of problem:
The aic7xxx and aic79xx drivers have high memory IO disabled (the
can_dma_32/single_sg_ok flags are unset in the SCSI driver template
structure). This is because the driver sources check for the
CONFIG_HIGHIO macro which, in the AS2.1 kernels, is persent in the
kernel .config, but not set in include/linux/autoconf.h.
This will lead to performance losses in systems wirth large memory.
Version-Release number of selected component (if applicable):
2.4.9-e.xy up to 2.4.9-e.38
Steps to Reproduce:
1.Install RHAS2.1 on system with aic7xxx or aic79xx controller and
2. Use "new" driver (aic7xxx 6.x.y) for aix7xxx.
3. Do I/O.
System uses bounce buffers.
System doesn't need bounce buffers.
I came a cross this problem accidentally by comparing the methods how
different driver sources check for the presence of the can_dma_32
field in the SCSI host template.
This issue is outside the scope of the current support status for RHEL2.1. No
fix is planned.