[PATCH i-g-t] tests/kms_cursor_legacy: Reduce debug loglevel dynamically

[Leo Li]

Hi Pranay,

This change can also increase log verbosity; we observe this with amdgpu.
Details inline.

On 2025-01-28 00:28, Pranay Samala wrote:
> This test is getting killed due to exceeding disk usage
> limit on CI environment because its logging to many logs.
> 
> So dynamically reducing the debug log level to 10.
> 
> Signed-off-by: Pranay Samala <pranay.samala at intel.com>
> ---
>   tests/kms_cursor_legacy.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/tests/kms_cursor_legacy.c b/tests/kms_cursor_legacy.c
> index 1f082df2d..533972cd4 100644
> --- a/tests/kms_cursor_legacy.c
> +++ b/tests/kms_cursor_legacy.c
> @@ -40,6 +40,7 @@
>   #include "igt_psr.h"
>   #include "igt_rand.h"
>   #include "igt_stats.h"
> +#include "igt_sysfs.h"
>   
>   /**
>    * SUBTEST: %s-%s
> @@ -1840,6 +1841,7 @@ igt_main
>   	};
>   
>   	igt_fixture {
> +		int dir, current_log_level;
>   		display.drm_fd = drm_open_driver_master(DRIVER_ANY);
>   		kmstest_set_vt_graphics_mode();
>   
> @@ -1850,6 +1852,15 @@ igt_main
>   		 * fetch is enabled, so switching PSR1 for this whole test.
>   		 */
>   		intel_psr2_restore = i915_psr2_sel_fetch_to_psr1(display.drm_fd, NULL);
> +
> +		dir = igt_sysfs_drm_module_params_open();
> +		if (dir >= 0) {
> +			current_log_level = igt_drm_debug_level_get(dir);
> +			close(dir);
> +
> +			if (current_log_level > 10)
> +				igt_drm_debug_level_update(10);

Isn't the DRM debug mask a bitmask?
https://elixir.bootlin.com/linux/v6.13.1/source/include/drm/drm_print.h#L97

So setting 10 isn't guaranteed to reduce verbosity, depending on how the DRM
driver uses the various drm_* debug prints.

What is guaranteed to reduce verbosity is to unset unwanted bits. Maybe that is
the better approach?

For example, instead of
`if (current_log_level > 10)`,

Do

`igt_drm_debug_level_update(current_log_level & !(DRM_UT_CORE | ...);`

Thanks,
Leo

> +		}
>   	}
>   
>   	igt_describe("Test checks how many cursor updates we can fit between vblanks "