It's currently KERN_WARNING. KERN_WARNING should be used for warnings, not success messages. I looked at the code, found that it's ACPI_INFO, and then got lost in all the indirection when trying to figure out where KERN_WARNING comes from.
This is because either ACPI_INFO or ACPI_WARNING actually invoke printk(KERN_CONT) at last, and the default message level of printk is KERN_WARNING. It looks like we might need to change the implementation of ACPI_INFO,ACPI_WARNING,etc to comply with the loglevel context.
Created attachment 215431 [details] add KERN_INFO for acpi_info This patch is to add KERN_INFO prefix for acpi_info
Created attachment 215901 [details] [PATCH] ACPICA: Utilities: Introduce facility to allow Linux to set correct logging levels OK. Please try the attached improvement. Thanks -Lv
Patch upstreamed to the ACPICA repo. Closing...
Please see bug 193531, where there seems to be some side effects from the patch.