Re: [PATCH] PM / OPP: fix debugfs files for 64-bit

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday 07 October 2015 18:33:24 Viresh Kumar wrote:
> Cc'ing Mike and Stephen..
> 
> On 07-10-15, 13:57, Greg Kroah-Hartman wrote:
> > On Wed, Oct 07, 2015 at 04:51:49PM +0530, Viresh Kumar wrote:
> > > On 07-10-15, 12:07, Greg Kroah-Hartman wrote:
> > > > Why would you be wanting to create a "unsigned long" as an api anyway?
> > > > Just force it to be u64 all the time, can't you do that?
> > > 
> > > Okay, so the variable in question (lets say frequency) is an 'unsigned
> > > long' and that's how all the APIs of clock framework expect/define
> > > it.
> > > 
> > > And you are probably saying that we do this:
> > > 
> > > unsigned long freq;
> > > 
> > > debugfs_create_u64((u64 *)&freq);
> > > 
> > > Right? Or are you asking to update clock APIs to be converted to u64?
> > 
> > Yes, they should be u64 as I doubt you want to debug problems that you
> > have in the driver where it works on a 64bit system but doesn't on a
> > 32bit one.
> 
> Firstly changing the clock API (and other similar APIs) to make
> frequency u64 instead of 'unsigned long', looks like a giant effort.
> There are too many users of those API, etc..
> 
> Over that, it might be good performance wise to use u32 for 32 bit
> systems and u64 for 64 bit one, to represent clock frequency and maybe
> that's why we chose unsigned long there.

I think it clearly makes sense to have a fixed length for each of these
members: either 32 bit is enough to represent all possible values, then
there is no need to make them 'long' on 64-bit architectures, or 32 bit
is not enough and then the code is broken on 32-bit architectures today
and should be fixed.

In my patch, I assumed that if 32-bit architectures work fine today, then
we don't need more range on 64-bit architectures either.

	Arnd