linux-kernel - Re: [PATCH v2 1/4] drm/dp: Add helper to set LTTPRs in transparent mode

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Message-ID: <3omcjrgfkdmw466ok7gej2jge25vtwzaiycwz2xgejwppyvkza@rhssgk7xz4hj>
Date: Wed, 11 Dec 2024 20:32:51 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Abel Vesa <abel.vesa@...aro.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>, 
	Danilo Krummrich <dakr@...hat.com>, Jani Nikula <jani.nikula@...ux.intel.com>, 
	Rodrigo Vivi <rodrigo.vivi@...el.com>, Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, 
	Tvrtko Ursulin <tursulin@...ulin.net>, Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org, 
	linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v2 1/4] drm/dp: Add helper to set LTTPRs in transparent
 mode

On Wed, Dec 11, 2024 at 03:42:27PM +0100, Johan Hovold wrote:
> On Wed, Dec 11, 2024 at 03:04:12PM +0200, Abel Vesa wrote:
>  
> > +/**
> > + * drm_dp_lttpr_set_transparent_mode - set the LTTPR in transparent mode
> > + * @aux: DisplayPort AUX channel
> > + * @enable: Enable or disable transparent mode
> > + *
> > + * Returns 0 on success or a negative error code on failure.
> > + */
> > +int drm_dp_lttpr_set_transparent_mode(struct drm_dp_aux *aux, bool enable)
> > +{
> > +	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
> > +			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
> > +	int ret = drm_dp_dpcd_writeb(aux, DP_PHY_REPEATER_MODE, val);
> > +
> > +	return ret == 1 ? 0 : ret;
> 
> This looks correct, but I had to go look at drm_dp_dpcd_writeb() to make
> sure it never returns 0 (for short transfers).
> 
> > +}
> > +EXPORT_SYMBOL(drm_dp_lttpr_set_transparent_mode);
> 
> This appears to be what the driver currently uses, but why not
> EXPORT_SYMBOL_GPL?

$ git grep EXPORT_SYMBOL drivers/gpu/drm/*.c | wc -l
962
$ git grep EXPORT_SYMBOL_GPL drivers/gpu/drm/*.c | wc -l
93


-- 
With best wishes
Dmitry