Re: [PATCH] hwmon: OCC drivers are PowerPC-only

[Guenter Roeck <linux@roeck-us.net>]

On Tue, Apr 09, 2019 at 09:44:33PM +0200, Jean Delvare wrote:
> Hi Eddie,
> 
> Thanks for the quick answer.
> 
> On Tue, 9 Apr 2019 10:20:22 -0500, Eddie James wrote:
> > On 4/9/19 7:45 AM, Jean Delvare wrote:
> > > Don't propose PowerPC-only drivers on other architectures, unless
> > > build-testing.  
> > 
> > This driver does NOT only run on PowerPC; rather it runs on a BMC 
> > processor connected to a PowerPC processor. BMC will most likely be ARM, 
> 
> Thanks for clarifying. So, you have a server with one or more PowerPC
> processors, running any operating system decided by the customer, and
> in the same system, is a BMC, running a Linux operating system provided
> by IBM? Do I understand it correctly?
> 
> > but shouldn't be restricted to that arch only.
> 
> Why not? Restricting drivers to the architectures or platforms where
> they make sense significantly eases the work of the maintainers of
> distribution kernels. Each new kernel version comes with several dozens
> of new options. Without hints, they have no idea what is needed on
> which architecture, and they either select everything, resulting in an
> overweight kernel forever, or nothing, resulting in missing features
> until someone complains.
> 
> Regardless of any dependency at the Kconfig level, the help text of
> these drivers should explain exactly what you wrote above. At the
> moment, the reader has no way to guess that the drivers only make sense
> for an embedded Linux running on a BMC. As I understand it now, general
> purpose distributions do not need these drivers, right? But for example
> SUSE kernels included them on all architectures. I just restricted them
> to ppc64, but apparently I was wrong and it should be disabled there
> too.
> 
> A good Kconfig help text should help the user decide whether they need
> the driver or not.
> 
> > > Also drop configuration symbol SENSORS_OCC which serves no purpose
> > > that I can see.
> > >
> > > Signed-off-by: Jean Delvare <jdelvare@suse.de>
> > > Cc: Eddie James <eajames@linux.ibm.com>
> > > Cc: Guenter Roeck <linux@roeck-us.net>
> > > ---
> > > SENSORS_OCC *would* serve a purpose if the common code between the
> > > POWER8 driver and the POWER9 driver would go in a separate, shared
> > > module, and occ-p8-hwmon and occ-p9-hwmon would only contain the
> > > specific code. This would avoid packaging the same code twice in 2
> > > separate modules, therefore saving some storage space for ppc
> > > distributions.  
> > 
> > Well you'd never have both P8 and P9 enabled at once, so space shouldn't 
> > be an issue. I agree this could be cleaner but I think I was getting 
> 
> Where "you" is IBM, provider of the embedded Linux running on the BMC?
> 
> > duplicate symbol errors for the compile test and so I did it this way. 
> > If this doesn't lead to errors in the compile test, I'm fine with this 
> > (without the change for PPC only though).
> 
> Dropping SENSORS_OCC can't result in duplicate symbols because it is a
> no-op. But while this is the easiest solution, it it not the cleanest
> in my opinion. OTOH, if you are certain that both modules will never be

I suspect that referred to symbols in common.c and sysfs.c, but I may
be wrong.

> shipped at the same time, then it indeed doesn't matter that much. I
> can provide a patch going in either direction. Guenter, any preference?
> 
The one I suggested in my other in my reply. Of course, I didn't test it,
so it may not work as suggested and require some additional tweaks.

Guenter