Re: [Intel-gfx] [PATCH 04/22] drm/amdgpu: Use drm_mode_copy()

[Harry Wentland <harry.wentland@amd.com>]

On 2022-02-18 05:03, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> struct drm_display_mode embeds a list head, so overwriting
> the full struct with another one will corrupt the list
> (if the destination mode is on a list). Use drm_mode_copy()
> instead which explicitly preserves the list head of
> the destination mode.
> 
> Even if we know the destination mode is not on any list
> using drm_mode_copy() seems decent as it sets a good
> example. Bad examples of not using it might eventually
> get copied into code where preserving the list head
> actually matters.
> 
> Obviously one case not covered here is when the mode
> itself is embedded in a larger structure and the whole
> structure is copied. But if we are careful when copying
> into modes embedded in structures I think we can be a
> little more reassured that bogus list heads haven't been
> propagated in.
> 
> @is_mode_copy@
> @@
> drm_mode_copy(...)
> {
> ...
> }
> 
> @depends on !is_mode_copy@
> struct drm_display_mode *mode;
> expression E, S;
> @@
> (
> - *mode = E
> + drm_mode_copy(mode, &E)
> |
> - memcpy(mode, E, S)
> + drm_mode_copy(mode, E)
> )
> 
> @depends on !is_mode_copy@
> struct drm_display_mode mode;
> expression E;
> @@
> (
> - mode = E
> + drm_mode_copy(&mode, &E)
> |
> - memcpy(&mode, E, S)
> + drm_mode_copy(&mode, E)
> )
> 
> @@
> struct drm_display_mode *mode;
> @@
> - &*mode
> + mode
> 
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Leo Li <sunpeng.li@amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> Cc: amd-gfx@lists.freedesktop.org
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c    | 4 ++--
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 +++---
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
> index fa20261aa928..673078faa27a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
> @@ -626,7 +626,7 @@ amdgpu_connector_fixup_lcd_native_mode(struct drm_encoder *encoder,
>  		if (mode->type & DRM_MODE_TYPE_PREFERRED) {
>  			if (mode->hdisplay != native_mode->hdisplay ||
>  			    mode->vdisplay != native_mode->vdisplay)
> -				memcpy(native_mode, mode, sizeof(*mode));
> +				drm_mode_copy(native_mode, mode);
>  		}
>  	}
>  
> @@ -635,7 +635,7 @@ amdgpu_connector_fixup_lcd_native_mode(struct drm_encoder *encoder,
>  		list_for_each_entry_safe(mode, t, &connector->probed_modes, head) {
>  			if (mode->hdisplay == native_mode->hdisplay &&
>  			    mode->vdisplay == native_mode->vdisplay) {
> -				*native_mode = *mode;
> +				drm_mode_copy(native_mode, mode);
>  				drm_mode_set_crtcinfo(native_mode, CRTC_INTERLACE_HALVE_V);
>  				DRM_DEBUG_KMS("Determined LVDS native mode details from EDID\n");
>  				break;
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index bd23c9e481eb..514280699ad5 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6318,7 +6318,7 @@ get_highest_refresh_rate_mode(struct amdgpu_dm_connector *aconnector,
>  		}
>  	}
>  
> -	aconnector->freesync_vid_base = *m_pref;
> +	drm_mode_copy(&aconnector->freesync_vid_base, m_pref);
>  	return m_pref;
>  }
>  
> @@ -6432,8 +6432,8 @@ create_stream_for_sink(struct amdgpu_dm_connector *aconnector,
>  		recalculate_timing = is_freesync_video_mode(&mode, aconnector);
>  		if (recalculate_timing) {
>  			freesync_mode = get_highest_refresh_rate_mode(aconnector, false);
> -			saved_mode = mode;
> -			mode = *freesync_mode;
> +			drm_mode_copy(&saved_mode, &mode);
> +			drm_mode_copy(&mode, freesync_mode);
>  		} else {
>  			decide_crtc_timing_for_drm_display_mode(
>  				&mode, preferred_mode, scale);