Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <68538a58-54e2-e82e-0789-52eb1cc6b66a@linaro.org>
Date:   Fri, 15 Apr 2022 03:48:07 +0300
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.0
Subject: Re: [RFC PATCH 3/6] drm/dp: Add is_hpd_asserted() callback to struct
 drm_dp_aux
Content-Language: en-GB
To:     Douglas Anderson <dianders@chromium.org>,
        dri-devel@lists.freedesktop.org
Cc:     Robert Foss <robert.foss@linaro.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Sankeerth Billakanti <quic_sbillaka@quicinc.com>,
        Philip Chen <philipchen@chromium.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Jani Nikula <jani.nikula@intel.com>,
        Kees Cook <keescook@chromium.org>,
        Lyude Paul <lyude@redhat.com>,
        Maxime Ripard <maxime@cerno.tech>, linux-kernel@vger.kernel.org
References: <20220409023628.2104952-1-dianders@chromium.org>
 <20220408193536.RFC.3.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <20220408193536.RFC.3.Icf57bb12233a47727013c6ab69eebf803e22ebc1@changeid>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 09/04/2022 05:36, Douglas Anderson wrote:
> Sometimes it's useful for users of the DP AUX bus (like panels) to be
> able to poll HPD. Let's add a callback that allows DP AUX busses
> drivers to provide this.
> 
> Suggested-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

> ---
> 
>   include/drm/dp/drm_dp_helper.h | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
> index dad1442c91df..a12951319573 100644
> --- a/include/drm/dp/drm_dp_helper.h
> +++ b/include/drm/dp/drm_dp_helper.h
> @@ -2021,6 +2021,20 @@ struct drm_dp_aux {
>   	ssize_t (*transfer)(struct drm_dp_aux *aux,
>   			    struct drm_dp_aux_msg *msg);
>   
> +	/**
> +	 * @is_hpd_asserted: returns true if HPD is asserted
> +	 *
> +	 * This is mainly useful for eDP panels drivers to query whether
> +	 * an eDP panel has finished powering on. This is an optional function.
> +	 *
> +	 * NOTE: this function specifically reports the state of the HPD pin
> +	 * that's associated with the DP AUX channel. This is different from
> +	 * the HPD concept in much of the rest of DRM which is more about
> +	 * physical presence of a display. For eDP, for instance, a display is
> +	 * assumed always present even if the HPD pin is deasserted.
> +	 */
> +	bool (*is_hpd_asserted)(struct drm_dp_aux *aux);
> +
>   	/**
>   	 * @i2c_nack_count: Counts I2C NACKs, used for DP validation.
>   	 */


-- 
With best wishes
Dmitry