Re: [PATCH i-g-t v4 2/2] lib/tests: make igt_get_output_max_bpc() return status and handle failures in callers

["Sharma, Swati2" <swati2.sharma@intel.com>]

Hi Pranay

Patch LGTM

Reviewed-by: Swati Sharma <swati2.sharma@intel.com>

On 09-06-2026 11:26 am, Pranay Samala wrote:
> Change igt_get_output_max_bpc() to return bool and fill an output parameter
> instead of asserting/requiring internally. This lets callers handle debugfs
> read/parse failures gracefully instead of failing inside the helper.
>
> Update test call sites to use the new boolean-return API so each test can
> decide how to handle max-bpc read failures. This separates read/parsing
> failures from capability checks and makes skip/continue decisions explicit
> with clearer logging, while preserving normal capability validation when
> max bpc is read successfully.
>
> v2:
> - Combine lib & test changes into single patch (Karthik)
>
> v3:
> - Add description for the helper (Swati)
>
> v4:
> - Rebase (Jason)
>
> Signed-off-by: Pranay Samala <pranay.samala@intel.com>
> ---
>   lib/igt_kms.c                          | 41 ++++++++++++++++++--------
>   lib/igt_kms.h                          |  2 +-
>   tests/amdgpu/amd_bypass.c              |  6 +++-
>   tests/amdgpu/amd_dp_dsc.c              | 10 ++++++-
>   tests/intel/kms_dsc.c                  |  5 +++-
>   tests/intel/kms_frontbuffer_tracking.c | 10 ++++++-
>   tests/kms_color_helper.c               |  5 +++-
>   tests/kms_dither.c                     |  9 +++++-
>   tests/kms_hdr.c                        | 16 ++++++++--
>   9 files changed, 83 insertions(+), 21 deletions(-)
>
> diff --git a/lib/igt_kms.c b/lib/igt_kms.c
> index 49bdbb358..244c24610 100644
> --- a/lib/igt_kms.c
> +++ b/lib/igt_kms.c
> @@ -6769,32 +6769,46 @@ bool igt_is_aux_less_alpm_enabled(int drmfd, char *connector_name)
>   
>   /**
>    * igt_get_output_max_bpc:
> - * @drmfd: A drm file descriptor
> - * @connector_name: Name of the libdrm connector we're going to use
> + * @output: Output to query.
> + * @maximum: Pointer to store the maximum supported bpc value.
> + *
> + * Read and parse the connector's debugfs output_bpc entry to obtain the
> + * maximum supported bits-per-component value.
>    *
> - * Returns: The maximum bpc from the connector debugfs.
> + * Returns: true on success, false on failure.
>    */
> -unsigned int igt_get_output_max_bpc(igt_output_t *output)
> +bool igt_get_output_max_bpc(igt_output_t *output, unsigned int *maximum)
>   {
>   	igt_display_t *display = output->display;
>   	int drmfd = display->drm_fd;
>   	char buf[24];
>   	char *start_loc;
>   	int fd, res;
> -	unsigned int maximum;
> +
> +	if (!maximum)
> +		return false;
> +
> +	*maximum = 0;
>   
>   	fd = igt_debugfs_connector_dir(drmfd, output->name, O_RDONLY);
> -	igt_assert(fd >= 0);
> +	if (fd < 0)
> +		return false;
>   
>   	res = igt_debugfs_simple_read(fd, "output_bpc", buf, sizeof(buf));
> -	igt_require(res > 0);
> -
>   	close(fd);
> +	if (res <= 0)
> +		return false;
>   
> -	igt_assert(start_loc = strstr(buf, "Maximum: "));
> -	igt_assert_eq(sscanf(start_loc, "Maximum: %u", &maximum), 1);
> +	buf[res < sizeof(buf) ? res : sizeof(buf) - 1] = '\0';
> +
> +	start_loc = strstr(buf, "Maximum: ");
> +	if (!start_loc)
> +		return false;
>   
> -	return maximum;
> +	if (sscanf(start_loc, "Maximum: %u", maximum) != 1)
> +		return false;
> +
> +	return true;
>   }
>   
>   /**
> @@ -6838,9 +6852,12 @@ unsigned int igt_get_crtc_current_bpc(igt_crtc_t *crtc)
>   static unsigned int get_current_bpc(igt_crtc_t *crtc, igt_output_t *output,
>   				    unsigned int bpc)
>   {
> -	unsigned int maximum = igt_get_output_max_bpc(output);
> +	unsigned int maximum;
>   	unsigned int current = igt_get_crtc_current_bpc(crtc);
>   
> +	igt_require_f(igt_get_output_max_bpc(output, &maximum),
> +		      "Failed to read max bpc for %s\n", igt_output_name(output));
> +
>   	igt_require_f(maximum >= bpc,
>   		      "Monitor doesn't support %u bpc, max is %u\n", bpc,
>   		      maximum);
> diff --git a/lib/igt_kms.h b/lib/igt_kms.h
> index e89f1f3b6..4b90577fc 100644
> --- a/lib/igt_kms.h
> +++ b/lib/igt_kms.h
> @@ -1322,7 +1322,7 @@ bool igt_fit_modes_in_bw(igt_display_t *display);
>   bool igt_has_lobf_debugfs(int drmfd, igt_output_t *output);
>   bool igt_get_i915_edp_lobf_status(int drmfd, char *connector_name);
>   bool igt_is_aux_less_alpm_enabled(int drmfd, char *connector_name);
> -unsigned int igt_get_output_max_bpc(igt_output_t *output);
> +bool igt_get_output_max_bpc(igt_output_t *output, unsigned int *maximum);
>   unsigned int igt_get_crtc_current_bpc(igt_crtc_t *crtc);
>   void igt_assert_output_bpc_equal(igt_crtc_t *crtc, igt_output_t *output,
>   				 unsigned int bpc);
> diff --git a/tests/amdgpu/amd_bypass.c b/tests/amdgpu/amd_bypass.c
> index 3c537ea9e..e59691f16 100644
> --- a/tests/amdgpu/amd_bypass.c
> +++ b/tests/amdgpu/amd_bypass.c
> @@ -323,6 +323,7 @@ static void bypass_8bpc_test(data_t *data)
>   	igt_display_t *display = &data->display;
>   	igt_fb_t fb;
>   	enum pattern ptn;
> +	unsigned int maximum;
>   
>   	test_init(data);
>   
> @@ -345,7 +346,10 @@ static void bypass_8bpc_test(data_t *data)
>   	 * Rx supports only up to 6bpc, Rx-crc will different from crtc-crc
>   	 * with 8bpc.
>   	 */
> -	igt_skip_on_f(igt_get_output_max_bpc(data->output) <= 6,
> +	igt_skip_on_f(!igt_get_output_max_bpc(data->output, &maximum),
> +		      "Failed to read max bpc for %s\n", igt_output_name(data->output));
> +
> +	igt_skip_on_f(maximum <= 6,
>   		      "check /sys/kernel/debug/dri/0/eDP-1 (connector)/output_bpc\n");
>   
>   	igt_create_fb(data->drm_fd, data->width, data->height,
> diff --git a/tests/amdgpu/amd_dp_dsc.c b/tests/amdgpu/amd_dp_dsc.c
> index 1742c7df4..dc71e903e 100644
> --- a/tests/amdgpu/amd_dp_dsc.c
> +++ b/tests/amdgpu/amd_dp_dsc.c
> @@ -480,11 +480,19 @@ static void test_dsc_bpc(data_t *data)
>   
>   	/* Find max supported bpc */
>   	for_each_crtc(&data->display, crtc) {
> +		unsigned int maximum;
> +
>   		output = data->output[crtc->crtc_index];
>   		if (!output || !igt_output_is_connected(output))
>   			continue;
>   		igt_info("Checking bpc support of conn %s\n", output->name);
> -		max_supported_bpc[crtc->crtc_index] = igt_get_output_max_bpc(output);
> +		if (!igt_get_output_max_bpc(output, &maximum)) {
> +			igt_info("Failed to read max bpc for conn %s\n", output->name);
> +			max_supported_bpc[crtc->crtc_index] = 0;
> +			continue;
> +		}
> +
> +		max_supported_bpc[crtc->crtc_index] = maximum;
>   	}
>   
>   	/* Setup all outputs */
> diff --git a/tests/intel/kms_dsc.c b/tests/intel/kms_dsc.c
> index 3687e795d..056fd37ae 100644
> --- a/tests/intel/kms_dsc.c
> +++ b/tests/intel/kms_dsc.c
> @@ -422,8 +422,11 @@ int igt_main_args("l", NULL, help_str, opt_handler, &data)
>   		igt_require(is_dsc_supported_by_source(data.drm_fd));
>   
>   		for_each_connected_output(&data.display, output) {
> +			unsigned int maximum;
> +
>   			if (is_dsc_supported_by_sink(data.drm_fd, output) &&
> -			    igt_get_output_max_bpc(output) >= MIN_DSC_BPC)
> +			    igt_get_output_max_bpc(output, &maximum) &&
> +			    maximum >= MIN_DSC_BPC)
>   				data.valid_output[data.count++] = output;
>   		}
>   	}
> diff --git a/tests/intel/kms_frontbuffer_tracking.c b/tests/intel/kms_frontbuffer_tracking.c
> index 37706cab5..3adf14bd7 100644
> --- a/tests/intel/kms_frontbuffer_tracking.c
> +++ b/tests/intel/kms_frontbuffer_tracking.c
> @@ -2281,6 +2281,8 @@ static void setup_drrs(void)
>   
>   static void setup_hdr(void)
>   {
> +	unsigned int maximum;
> +
>   	if (!igt_output_has_prop(prim_mode_params.output, IGT_CONNECTOR_MAX_BPC) ||
>   	    !igt_output_get_prop(prim_mode_params.output, IGT_CONNECTOR_MAX_BPC) ||
>   	    !igt_output_supports_hdr(prim_mode_params.output)) {
> @@ -2294,7 +2296,13 @@ static void setup_hdr(void)
>   		return;
>   	}
>   
> -	if (igt_get_output_max_bpc(prim_mode_params.output) < 10) {
> +	if (!igt_get_output_max_bpc(prim_mode_params.output, &maximum)) {
> +		igt_info("Can't test HDR: Failed to read max bpc for %s.\n",
> +			 igt_output_name(prim_mode_params.output));
> +		return;
> +	}
> +
> +	if (maximum < 10) {
>   		igt_info("Can't test HDR: %s doesn't support 10 bpc.\n", igt_output_name(prim_mode_params.output));
>   		return;
>   	}
> diff --git a/tests/kms_color_helper.c b/tests/kms_color_helper.c
> index 24663444a..a50ac3a37 100644
> --- a/tests/kms_color_helper.c
> +++ b/tests/kms_color_helper.c
> @@ -40,7 +40,10 @@ bool crtc_output_combo_valid(data_t *data, igt_crtc_t *crtc)
>   bool
>   panel_supports_deep_color(igt_output_t *output)
>   {
> -	unsigned int maximum = igt_get_output_max_bpc(output);
> +	unsigned int maximum;
> +
> +	if (!igt_get_output_max_bpc(output, &maximum))
> +		return false;
>   
>   	igt_info("Max supported bit depth: %d\n", maximum);
>   
> diff --git a/tests/kms_dither.c b/tests/kms_dither.c
> index ca367db61..236e5c7c0 100644
> --- a/tests/kms_dither.c
> +++ b/tests/kms_dither.c
> @@ -206,6 +206,7 @@ run_dither_test(data_t *data, int fb_bpc, int fb_format, int output_bpc)
>   
>   	for_each_connected_output(display, output) {
>   		igt_crtc_t *crtc;
> +		unsigned int maximum;
>   
>   		if (!is_supported(output)) {
>   			igt_info("Output %s: Doesn't support \"max bpc\" property.\n",
> @@ -213,7 +214,13 @@ run_dither_test(data_t *data, int fb_bpc, int fb_format, int output_bpc)
>   			continue;
>   		}
>   
> -		if (igt_get_output_max_bpc(output) < output_bpc) {
> +		if (!igt_get_output_max_bpc(output, &maximum)) {
> +			igt_info("Output %s: Failed to read max bpc.\n",
> +				 igt_output_name(output));
> +			continue;
> +		}
> +
> +		if (maximum < output_bpc) {
>   			igt_info("Output %s: Doesn't support %d-bpc.\n",
>   				 igt_output_name(output), output_bpc);
>   			continue;
> diff --git a/tests/kms_hdr.c b/tests/kms_hdr.c
> index 7127a56b3..ebf468e0d 100644
> --- a/tests/kms_hdr.c
> +++ b/tests/kms_hdr.c
> @@ -254,6 +254,7 @@ static void test_bpc_switch(data_t *data, uint32_t flags)
>   
>   	for_each_connected_output(display, output) {
>   		igt_crtc_t *crtc;
> +		unsigned int maximum;
>   
>   		if (!has_max_bpc(output)) {
>   			igt_info("%s: Doesn't support IGT_CONNECTOR_MAX_BPC.\n",
> @@ -261,7 +262,12 @@ static void test_bpc_switch(data_t *data, uint32_t flags)
>   			continue;
>   		}
>   
> -		if (igt_get_output_max_bpc(output) < 10) {
> +		if (!igt_get_output_max_bpc(output, &maximum)) {
> +			igt_info("%s: Failed to read max bpc.\n", igt_output_name(output));
> +			continue;
> +		}
> +
> +		if (maximum < 10) {
>   			igt_info("%s: Doesn't support 10 bpc.\n", igt_output_name(output));
>   			continue;
>   		}
> @@ -535,6 +541,7 @@ static void test_hdr(data_t *data, uint32_t flags)
>   
>   	for_each_connected_output(display, output) {
>   		igt_crtc_t *crtc;
> +		unsigned int maximum;
>   
>   		/* To test HDR, 10 bpc is required, so we need to
>   		 * set MAX_BPC property to 10bpc prior to setting
> @@ -559,7 +566,12 @@ static void test_hdr(data_t *data, uint32_t flags)
>   			continue;
>   		}
>   
> -		if (igt_get_output_max_bpc(output) < 10) {
> +		if (!igt_get_output_max_bpc(output, &maximum)) {
> +			igt_info("%s: Failed to read max bpc.\n", igt_output_name(output));
> +			continue;
> +		}
> +
> +		if (maximum < 10) {
>   			igt_info("%s: Doesn't support 10 bpc.\n", igt_output_name(output));
>   			continue;
>   		}