Il 12/03/2010 23:48, Andrew Morton ha scritto: > On Wed, 10 Mar 2010 13:15:25 +0100 > Marco Stornelli <marco.stornelli@xxxxxxxxx> wrote: > >> 2010/3/10 Yuasa Yoichi <yuasa@xxxxxxxxxxxxxx>: >>> 2010/3/10 Marco Stornelli <marco.stornelli@xxxxxxxxx>: >>>> 2010/3/10 Yuasa Yoichi <yuasa@xxxxxxxxxxxxxx>: >> I meant with the "classic" use of mtdoops, therefore with a flash >> partition without use MTD_RAM. Using MTD_RAM, it's more or less the >> same thing, with the exception of "where" you want deploy the log. For >> example: if in your system you have got a nvram you can use it without >> problem, you need to specify the address of the nvram to the module. >> Very simple. I think it's a small driver but very useful, feedback >> from other embedded guys are welcome. > > Seems sensible to me. If you have a machine whose memory is persistent > across reboots then you reserve an arbitrary 4k hunk of memory for > collecting oops traces, yes? Yes. > > What tools are used for displaying that memory on the next boot? How > do those tools distinguish between "valid oops trace" and "garbage > because it was just powered on"? A magic signature? For my test I used the program devmem2 to dump the log. In general, you can read the memory via /dev/mem. There's an header plus a timestamp of the log. The memory is initialized with blank spaces and the size of the record is fixed at 4k, so if a program/script doesn't find the header at next 4k, it means there's garbage and it can stop the read operation. > > Should the kernel provide the 4k of memory rather than (or in addition > to) requiring that the system administrator reserve it and tell the > kernel about it? That'd be a matter of creating a linker section which > isn't cleared out by the startup code. > > Yes, it can be an option. My first idea was to write a "general" driver, with an address in input that it can be related to the reserved RAM as an NVRAM in the system, however it can be a good idea, why not. Marco -- 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
