Re: PM / OPP: Add clock-latency-ns support

[Dan Carpenter <dan.carpenter@oracle.com>]

On Tue, Aug 11, 2015 at 01:42:28PM +0530, Viresh Kumar wrote:
> On 10-08-15, 19:38, Dan Carpenter wrote:
> > Hello Viresh Kumar,
> > 
> > The patch 3ca9bb33c627: "PM / OPP: Add clock-latency-ns support" from
> > Jul 29, 2015, leads to the following static checker warning:
> > 
> > 	drivers/base/power/opp.c:949 _opp_add_static_v2()
> > 	warn: passing casted pointer '&new_opp->clock_latency_ns' to 'of_property_read_u32()' 64 vs 32.
> > 
> > drivers/base/power/opp.c
> >    946          new_opp->np = np;
> >    947          new_opp->dynamic = false;
> >    948          new_opp->available = true;
> >    949          of_property_read_u32(np, "clock-latency-ns",
> >    950                               (u32 *)&new_opp->clock_latency_ns);
> >                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^
> > 
> > This code will break on 64 bit, big endian machines.  I doin't know if
> > that is an issue for this driver.  I saw this was in the power/
> > directory and I spent a minute googling to see if PowerPC machines are
> > big endian...  :P
> > 
> >    951  
> >    952          ret = opp_get_microvolt(new_opp, dev);
> >    953          if (ret)
> >    954                  goto free_opp;
> >    955  
> > 
> > Also:
> > 
> > 	drivers/base/power/opp.c:956 _opp_add_static_v2()
> > 	warn: passing casted pointer '&new_opp->u_amp' to 'of_property_read_u32()' 64 vs 32.
> 
> Hi Dan,
> 
> The problem is that the value here is of type 'unsigned long' which is
> 32/64 bit on 32/64 bit machines.

Yep.  It won't work on 64 bit big endian machines as described earlier.

> 
> So, I looked at how other places in code has done it, and that's what
> I found.

It's not portable.  Sometimes we don't care about that because we know
we don't care about 64 bit big endian systems.  Hence, my email.

regards,
dan carpenter