linux-kernel - Re: [PATCH] drm/radeon: fix uninitialized bool variable

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Date:   Mon, 20 Sep 2021 09:44:01 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Zhiwei Yang <yangzhiwei@...ontech.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>
Cc:     Christian König <christian.koenig@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/radeon: fix uninitialized bool variable



Am 18.09.21 um 11:41 schrieb Zhiwei Yang:
> The bool variable detected_hpd_without_ddc in struct radeon_connector
> is uninitialized when first used, that may cause unnecessary ddc ops.
> Make it as false when a new connector is alloced.
>
> Signed-off-by: Zhiwei Yang <yangzhiwei@...ontech.com>
> ---
>   drivers/gpu/drm/radeon/radeon_connectors.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
> index fe12d9d91d7a..c1987a66373f 100644
> --- a/drivers/gpu/drm/radeon/radeon_connectors.c
> +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
> @@ -1866,6 +1866,7 @@ radeon_add_atom_connector(struct drm_device *dev,
>   	bool shared_ddc = false;
>   	bool is_dp_bridge = false;
>   	bool has_aux = false;
> +	bool detected_hpd_without_ddc = false;

In general good catch, but I don't see the need for a local variable here.

Just initialize the member directly or even better change the allocation 
of the connector into a kzalloc().

Christian.

>   
>   	if (connector_type == DRM_MODE_CONNECTOR_Unknown)
>   		return;
> @@ -1923,6 +1924,7 @@ radeon_add_atom_connector(struct drm_device *dev,
>   	radeon_connector->shared_ddc = shared_ddc;
>   	radeon_connector->connector_object_id = connector_object_id;
>   	radeon_connector->hpd = *hpd;
> +	radeon_connector->detected_hpd_without_ddc = detected_hpd_without_ddc;
>   
>   	radeon_connector->router = *router;
>   	if (router->ddc_valid || router->cd_valid) {
> @@ -2384,6 +2386,7 @@ radeon_add_legacy_connector(struct drm_device *dev,
>   	struct radeon_connector *radeon_connector;
>   	struct i2c_adapter *ddc = NULL;
>   	uint32_t subpixel_order = SubPixelNone;
> +	bool detected_hpd_without_ddc = false;
>   
>   	if (connector_type == DRM_MODE_CONNECTOR_Unknown)
>   		return;
> @@ -2414,6 +2417,7 @@ radeon_add_legacy_connector(struct drm_device *dev,
>   	radeon_connector->devices = supported_device;
>   	radeon_connector->connector_object_id = connector_object_id;
>   	radeon_connector->hpd = *hpd;
> +	radeon_connector->detected_hpd_without_ddc = detected_hpd_without_ddc;
>   
>   	switch (connector_type) {
>   	case DRM_MODE_CONNECTOR_VGA: