Re: [Qemu-ppc] [PATCH 1/1] target-ppc: Support rtas_get_sysparm(PROCESSOR_MODULE_INFO)

[Alexey Kardashevskiy]

On 10/31/2015 03:33 AM, Sukadev Bhattiprolu wrote:
> Alexey Kardashevskiy address@hidden wrote:
>
> Thanks for the review. Agree with your other comments and will address
> them.
>
> | >+#include <string.h>
> | >+#include <errno.h>
> | >+
> | >+/*
> | >+ * TODO: <fts.h> doesn't like __USE_FILE_OFFSET64 but hopefully we don't
> |
> |
> | That's ugly :-/ Google is saying there is
> | http://linux.die.net/man/3/ftw which looks newer => better.
>
> Like I say below...
>
> |
> |
> | >+ *     need to deal with large file offsets in /proc/device-tree. If we
> | >+ *     must, we should fall back to walking the tree with opendir().
> | >+ *     Another alternative is nftw() but that requires us to use global
> | >+ *     variables to keep the counts of chips/cores etc so we need to
> | >+ *     serialize access to the globals.
> | >+ */
>
> for each file, nftw() calls the 'fn()' parameter but there is no state
> info saved from one call to next. So if we find a chip and want to increment
> a counter, we need a global variable and some serialization. I was trying
> to keep it simple, given that device-tree files we care about are not large.
> But should we add a mutex and increment global counts instead?

I do not really understand why you need to walk the whole tree while the 
nodes you are interested in are just these:

/proc/device-tree/cpus/PowerPC,address@hidden/ibm,chip-id
/proc/device-tree/cpus/PowerPC,address@hidden/device-type
/proc/device-tree/address@hidden/ibm,chip-id
/proc/device-tree/address@hidden/ibm,hw-module-id

These are known locations which are unlike to change.

btw why do you double-check for PowerPC,address@hidden/device-type to have "cpu"? 
Can it be something different? On what system?

And what is "ibm,hw-module-id"? None of my systems has it - Tuleta, 
Firestone. Is that NUMA?

Another thought - all CPUs can be enumerated via 
/sys/devices/system/cpu/cpu* and nodes - via /sys/devices/system/nodes, 
they all have symlinks to each other and to the device tree, might be 
useful for this task, not sure though.



--
Alexey