Re: [PATCH i-g-t 1/4] tests/intel/kms_frontbuffer_tracking: update the outdated fbc status checks

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 26 Mar 2026, Vinod Govindapillai <vinod.govindapillai@intel.com> wrote:
> Replace the fbc status check for "mode too large for compression" wchich
> is no longer being set by the driver with "plane size too big" and
> "surface size too big" fbc status checks.
>
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  tests/intel/kms_frontbuffer_tracking.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/tests/intel/kms_frontbuffer_tracking.c b/tests/intel/kms_frontbuffer_tracking.c
> index c16f63199..e764c9ce1 100644
> --- a/tests/intel/kms_frontbuffer_tracking.c
> +++ b/tests/intel/kms_frontbuffer_tracking.c
> @@ -1664,15 +1664,23 @@ static bool fbc_stride_not_supported(void)
>  	char buf[128];
>  
>  	debugfs_read_crtc("i915_fbc_status", buf);
> -	return strstr(buf, "FBC disabled: framebuffer stride not supported\n");
> +	return strstr(buf, "FBC disabled: stride not supported\n");
>  }
>  
> -static bool fbc_mode_too_large(void)
> +static bool fbc_plane_size_too_big(void)
>  {
>  	char buf[128];
>  
>  	debugfs_read_crtc("i915_fbc_status", buf);
> -	return strstr(buf, "FBC disabled: mode too large for compression\n");
> +	return strstr(buf, "FBC disabled: plane size too big\n");
> +}
> +
> +static bool fbc_surface_size_too_big(void)
> +{
> +	char buf[128];
> +
> +	debugfs_read_crtc("i915_fbc_status", buf);
> +	return strstr(buf, "FBC disabled: surface size too big\n");
>  }
>  
>  static bool fbc_psr_not_possible(void)
> @@ -2356,7 +2364,8 @@ static void do_status_assertions(int flags)
>  	if (flags & ASSERT_FBC_ENABLED) {
>  		igt_require(!fbc_not_enough_stolen());
>  		igt_require(!fbc_stride_not_supported());
> -		igt_require(!fbc_mode_too_large());
> +		igt_require(!fbc_plane_size_too_big());
> +		igt_require(!fbc_surface_size_too_big());

I think the problem with the current implementation and this series is
that it still keeps all those i915_fbc_status reads in place, instead of
reading it *once* and then figuring it out.

You could e.g. have a function that reads i915_fbc_status, parses it
into, I don't know, an enum on the igt side, with some handling of
unknown "FBC disabled: xxx" messages, and returns that.

And then you get that status once, and check that, instead of reading
the file N times.

BR,
Jani.

>  		igt_require(!fbc_psr_not_possible());
>  		if (!intel_fbc_wait_until_enabled(prim_mode_params.crtc)) {
>  			igt_assert_f(intel_fbc_is_enabled(prim_mode_params.crtc, IGT_LOG_WARN),

-- 
Jani Nikula, Intel