linux-kernel - Re: [PATCH] drm: Add a debug message when getting a prop is missing

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Date:   Tue, 17 May 2022 10:51:14 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Mark Yacoub <markyacoub@...omium.org>
Cc:     David Airlie <airlied@...ux.ie>, markyacoub@...omium.org,
        linux-kernel@...r.kernel.org, seanpaul@...omium.org,
        dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>, markyacoub@...gle.com
Subject: Re: [PATCH] drm: Add a debug message when getting a prop is missing

On Tue, 10 May 2022, Mark Yacoub <markyacoub@...omium.org> wrote:
> [Why]
> If a connector property is attached but
> drm_atomic_connector_get_property doesn't handle a case for it,
> modeteset will crash with a segfault without.
>
> [How]
> Add a debug message indicating that a connector property is not handled
> when user space is trying to read it.
>
> TEST=modetest
>
> Signed-off-by: Mark Yacoub <markyacoub@...omium.org>
> ---
>  drivers/gpu/drm/drm_atomic_uapi.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index acb1ee93d206..36b0f664dd80 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -884,6 +884,12 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
>  		return connector->funcs->atomic_get_property(connector,
>  				state, property, val);
>  	} else {
> +		// LOG that the kernel is missing handling this property as a case here.

The comment is unnecessary, and we also don't use // comments.

> +		drm_dbg_atomic(
> +			dev,
> +			"[CONNECTOR:%d:%s] Get Property [PROP:%d:%s] is not handled\n",
> +			connector->base.id, connector->name, property->base.id,
> +			property->name);

Why not use the same message as in drm_atomic_connector_set_property()?

Blank line here.

BR,
Jani.

>  		return -EINVAL;
>  	}

-- 
Jani Nikula, Intel Open Source Graphics Center