[ofa-general] Re: [PATCH v2] mlx4: make firmware diagnostic counters available via sysfs

[Jack Morgenstein]

On Wednesday 09 July 2008 00:15, Roland Dreier wrote:
> Looking at this in the context of what's queued already -- would it make
> sense to expose this via the protocol counters stuff that went in for
> iWARP?
> 
>  - R.
The firmware diagnostic counters are not IB-protocol counters -- they are low-level
device-specific (i.e., ConnectX-specific) counters.

As such, I think the code to implement them belongs in the low-level driver layer.

The problem here is that the sysfs counter file names are specified in the core
layer (core/sysfs.c) via the IW_STATS_ENTRY macro at compilation time.

If we are to implement exposing these firmware counters in the core layer, we need
a low-level driver API which would allow the low-level driver to pass to the core
layer at run time a vector of counter names, and we would then need to do all the
compile-time operations (DEVICE_ATTR,  declaration of all the "show functions", etc)
at run time.

It looks to me that this would be messy.  For example, each "show" method is specific to
one counter-name "file".  We would then need to pre-declare (at compile time) a group
of "show" methods whose names are the offsets, rather than the counter-name
(e.g., device_name ## "counter-1", etc.), and this would have the effect of limiting
the max number of counters we could generate.

Despite the great code similarity, I think it is preferable to leave the firmware diagnostic
counters in the mlx4 layer at this point.

- Jack