linux-kernel - Re: [PATCH v3 2/2] drm/dp: drop the size parameter from drm_dp_vsc_sdp

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Date: Thu, 22 Feb 2024 14:09:16 -0500
From: Rodrigo Vivi <rodrigo.vivi@...el.com>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
CC: <dri-devel@...ts.freedesktop.org>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>, Jani Nikula <jani.nikula@...ux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin
	<tvrtko.ursulin@...ux.intel.com>, <robdclark@...il.com>,
	<freedreno@...ts.freedesktop.org>, <dmitry.baryshkov@...aro.org>,
	<intel-gfx@...ts.freedesktop.org>, <ville.syrjala@...ux.intel.com>,
	<quic_jesszhan@...cinc.com>, <linux-kernel@...r.kernel.org>,
	<intel-xe@...ts.freedesktop.org>
Subject: Re: [PATCH v3 2/2] drm/dp: drop the size parameter from
 drm_dp_vsc_sdp_pack()

On Tue, Feb 20, 2024 at 11:53:47AM -0800, Abhinav Kumar wrote:
> Currently the size parameter of drm_dp_vsc_sdp_pack() is always
> the size of struct dp_sdp. Hence lets drop this parameter and
> use sizeof() directly.
> 
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>

it looks indeed an unecessary check.
you can convert my ack to a

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>

and the ack to take this through drm-misc if needed

> ---
>  drivers/gpu/drm/display/drm_dp_helper.c | 8 ++------
>  drivers/gpu/drm/i915/display/intel_dp.c | 3 +--
>  include/drm/display/drm_dp_helper.h     | 3 +--
>  3 files changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> index 6c91f400ecb1..10ee82e34de7 100644
> --- a/drivers/gpu/drm/display/drm_dp_helper.c
> +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> @@ -2918,19 +2918,15 @@ EXPORT_SYMBOL(drm_dp_vsc_sdp_log);
>   * @vsc: vsc sdp initialized according to its purpose as defined in
>   *       table 2-118 - table 2-120 in DP 1.4a specification
>   * @sdp: valid handle to the generic dp_sdp which will be packed
> - * @size: valid size of the passed sdp handle
>   *
>   * Returns length of sdp on success and error code on failure
>   */
>  ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc,
> -			    struct dp_sdp *sdp, size_t size)
> +			    struct dp_sdp *sdp)
>  {
>  	size_t length = sizeof(struct dp_sdp);
>  
> -	if (size < length)
> -		return -ENOSPC;
> -
> -	memset(sdp, 0, size);
> +	memset(sdp, 0, sizeof(struct dp_sdp));
>  
>  	/*
>  	 * Prepare VSC Header for SU as per DP 1.4a spec, Table 2-119
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index a9458df475e2..e13121dc3a03 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -4181,8 +4181,7 @@ static void intel_write_dp_sdp(struct intel_encoder *encoder,
>  
>  	switch (type) {
>  	case DP_SDP_VSC:
> -		len = drm_dp_vsc_sdp_pack(&crtc_state->infoframes.vsc, &sdp,
> -					  sizeof(sdp));
> +		len = drm_dp_vsc_sdp_pack(&crtc_state->infoframes.vsc, &sdp);
>  		break;
>  	case HDMI_PACKET_TYPE_GAMUT_METADATA:
>  		len = intel_dp_hdr_metadata_infoframe_sdp_pack(dev_priv,
> diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> index 8474504d4c88..1f41994796d3 100644
> --- a/include/drm/display/drm_dp_helper.h
> +++ b/include/drm/display/drm_dp_helper.h
> @@ -812,7 +812,6 @@ int drm_dp_bw_overhead(int lane_count, int hactive,
>  		       int bpp_x16, unsigned long flags);
>  int drm_dp_bw_channel_coding_efficiency(bool is_uhbr);
>  
> -ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc,
> -			    struct dp_sdp *sdp, size_t size);
> +ssize_t drm_dp_vsc_sdp_pack(const struct drm_dp_vsc_sdp *vsc, struct dp_sdp *sdp);
>  
>  #endif /* _DRM_DP_HELPER_H_ */
> -- 
> 2.34.1
>