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]> --- 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
