Re: [Intel-gfx] [PATCH] drm/i915/display: pre-initialize some values in probe_gmdid_display()

["Coelho, Luciano" <luciano.coelho@intel.com>]

On Thu, 2023-06-22 at 10:08 +0000, Kandpal, Suraj wrote:
> > On Tue, 2023-06-20 at 10:30 +0000, Kandpal, Suraj wrote:
> > > > When intel_display_device_probe() (and, subsequently,
> > > > probe_gmdid_display()) returns, the caller expects ver, rel and
> > > > step
> > > > to be initialized.  Since there's no way to check that there
> > > > was a
> > > > failure and no_display was returned without some further
> > > > refactoring, pre- initiliaze all these values to zero to keep
> > > > it
> > > > simple and safe.
> > > > 
> > > > Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
> > > 
> > > Looks okay to me just a small suggestion/question below.
> > > 
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_display_device.c | 9
> > > > +++++++++
> > > >  1 file changed, 9 insertions(+)
> > > > 
> > > > diff --git
> > > > a/drivers/gpu/drm/i915/display/intel_display_device.c
> > > > b/drivers/gpu/drm/i915/display/intel_display_device.c
> > > > index 464df1764a86..fb6354e9e704 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_display_device.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_display_device.c
> > > > @@ -731,6 +731,15 @@ probe_gmdid_display(struct
> > > > drm_i915_private
> > > > *i915, u16 *ver, u16 *rel, u16 *step
> > > >  	u32 val;
> > > >  	int i;
> > > > 
> > > > +	/* The caller expects to ver, rel and step to be
> > > > initialized
> > > > +	 * here, and there's no good way to check when there
> > > > was a
> > > > +	 * failure and no_display was returned.  So initialize
> > > > all
> > > > these
> > > > +	 * values here zero, to be sure.
> > > > +	 */
> > > > +	*ver = 0;
> > > > +	*rel = 0;
> > > > +	*step = 0;
> > > > +
> > > 
> > > From what I can see this is only called from
> > > intel_display_device_probe() which is in turn called from
> > > intel_device_info_driver_create() where the above variables are
> > > defined maybe we initialize these values there itself.
> > 
> > Thanks for the review!
> > 
> > I thought about initializing the variables on the caller side, but
> > reckoned that
> > it would be more intuitive to initialize them in the
> > probe_gmdid_display() function instead, because the caller expects
> > those
> > values to be set in successful cases and there's no way for it to
> > know whether
> > there was a failure or not (because we return a pointer to local
> > no_display
> > structure that the caller doesn't know about).
> > 
> > Obviously with the current code in the caller, that doesn't make
> > much
> > difference, but I thought it was cleaner as I did.
> > 
> > But I'm okay to change it and initialize them at the caller, so
> > just let me know
> > if you want that.
> 
> I don’t think it needs to be changed then and the explanation looks
> reasonable.
> So this LGTM
> 
> Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
> 

Thanks, Suraj! Can someone merge this for me, please?

--
Cheers,
Luca.