On Wed, Feb 23, 2022 at 03:13:03PM +0200, Ville Syrjala wrote: > From: Ville Syrjälä <[email protected]> > > bigjoiner_pipes==0 leads bigjoiner_master_pipe() to > do BIT(ffs(0)-1) which is undefined behaviour. The code should > actually still work fine since the only place we provoke > that is intel_crtc_bigjoiner_slave_pipes() and it'll bitwise > AND the result with 0, so doesn't really matter what we get > out of bigjoiner_master_pipe(). But best not provoke undefined > behaviour anyway. > > Reported-by: kernel test robot <[email protected]> > Fixes: a6e7a006f5d5 ("drm/i915: Change bigjoiner state tracking to use the > pipe bitmask") > Signed-off-by: Ville Syrjälä <[email protected]>
Reviewed-by: Manasi Navare <[email protected]> Manasi > --- > drivers/gpu/drm/i915/display/intel_display.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c > b/drivers/gpu/drm/i915/display/intel_display.c > index 80b19c304c43..f3f5f11a5abf 100644 > --- a/drivers/gpu/drm/i915/display/intel_display.c > +++ b/drivers/gpu/drm/i915/display/intel_display.c > @@ -346,7 +346,10 @@ static enum pipe bigjoiner_master_pipe(const struct > intel_crtc_state *crtc_state > > u8 intel_crtc_bigjoiner_slave_pipes(const struct intel_crtc_state > *crtc_state) > { > - return crtc_state->bigjoiner_pipes & > ~BIT(bigjoiner_master_pipe(crtc_state)); > + if (crtc_state->bigjoiner_pipes) > + return crtc_state->bigjoiner_pipes & > ~BIT(bigjoiner_master_pipe(crtc_state)); > + else > + return 0; > } > > bool intel_crtc_is_bigjoiner_slave(const struct intel_crtc_state *crtc_state) > -- > 2.34.1 >
