[PATCH] drm/i915/backlight: Fix divide by 0 error in i9xx_set_backlight

[Kandpal, Suraj]

> Subject: Re: [PATCH] drm/i915/backlight: Fix divide by 0 error in
> i9xx_set_backlight
> 
> On Tue, 19 Aug 2025, Suraj Kandpal <suraj.kandpal at intel.com> wrote:
> > pwm_level_max maybe 0 we do throw a warning but move ahead with
> > execution which may later cause a /0 error.
> 
> This is not supposed to happen, so don't overcomplicate.
> 
> if (warn on)
> 	return
> 

Sure will return from here

Regards,
Suraj Kandpal

> >
> > Signed-off-by: Suraj Kandpal <suraj.kandpal at intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_backlight.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c
> > b/drivers/gpu/drm/i915/display/intel_backlight.c
> > index e007380e9a63..d0e9de8ab834 100644
> > --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> > +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> > @@ -234,6 +234,7 @@ static void i9xx_set_backlight(const struct
> drm_connector_state *conn_state, u32
> >  	struct intel_connector *connector = to_intel_connector(conn_state-
> >connector);
> >  	struct intel_display *display = to_intel_display(connector);
> >  	struct intel_panel *panel = &connector->panel;
> > +	u32 max_level = panel->backlight.pwm_level_max ?: 1;
> >  	u32 tmp, mask;
> >
> >  	drm_WARN_ON(display->drm, panel->backlight.pwm_level_max == 0);
> @@
> > -242,7 +243,7 @@ static void i9xx_set_backlight(const struct
> drm_connector_state *conn_state, u32
> >  		struct pci_dev *pdev = to_pci_dev(display->drm->dev);
> >  		u8 lbpc;
> >
> > -		lbpc = level * 0xfe / panel->backlight.pwm_level_max + 1;
> > +		lbpc = level * 0xfe / max_level + 1;
> >  		level /= lbpc;
> >  		pci_write_config_byte(pdev, LBPC, lbpc);
> >  	}
> 
> --
> Jani Nikula, Intel