On Wed, May 28, 2008 at 11:01 PM, Rob Landley wrote: > On Tuesday 27 May 2008 17:31:42 T Ziomek wrote: >> If I understand correctly David is talking about logging some trace-like >> info (so it exists before a HW watchdog expires), and having it somewhere >> "safe" from being disturbed by a HW reset. > > The standard way of doing this is to use the mem= kernel command line > parameter to tell the system it has less memory than it does, and using > what's left as a ramdisk. Years ago I saw some userspace thing running as > root mmap() /dev/mem (or whatever they're calling it these days) and log to > it. In theory you could even set the dmesg buffer up at the end of physical > memory with a smallish kernel patch, make it big, and set the kernel to doing > verbose printks. > > The trick is A) knowing the absolute physical address at which your debug > buffer lives so you can find it after the reboot, B) convincing the system to > do something useful with it on reboot rather than just overwriting it with > fresh log data. how about the fact that when the core resets, the memory controller is often reset as well ? that external memory is going to degrade. or do we just bite our thumb and weather the few random bit errors ? -mike -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
