linux-kernel - Re: [PATCH v4 14/23] drm/tilcdc: Provide ddc symlink in connector sysfs directory

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Message-ID: <3ad60be5-49cf-4017-4b74-53a2d6272deb@collabora.com>
Date:   Tue, 23 Jul 2019 14:44:50 +0200
From:   Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Shawn Guo <shawnguo@...nel.org>, kernel@...labora.com,
        linux-samsung-soc@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, Sean Paul <sean@...rly.run>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        Kukjin Kim <kgene@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Dave Airlie <airlied@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jonas Karlman <jonas@...boo.se>, linux-arm-msm@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, Jyri Sarha <jsarha@...com>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Mamta Shukla <mamtashukla555@...il.com>,
        linux-mediatek@...ts.infradead.org,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        linux-tegra@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Vincent Abriou <vincent.abriou@...com>,
        linux-arm-kernel@...ts.infradead.org,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        amd-gfx@...ts.freedesktop.org,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Douglas Anderson <dianders@...omium.org>,
        Todor Tomov <todor.tomov@...aro.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Huang Rui <ray.huang@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Alex Deucher <alexander.deucher@....com>,
        freedreno@...ts.freedesktop.org,
        Christian König <christian.koenig@....com>,
        Gerd Hoffmann <kraxel@...hat.com>
Subject: Re: [PATCH v4 14/23] drm/tilcdc: Provide ddc symlink in connector
 sysfs directory

Hi Sam,

W dniu 23.07.2019 o 11:05, Sam Ravnborg pisze:
> Hi Andrzej
> 
> On Thu, Jul 11, 2019 at 01:26:41PM +0200, Andrzej Pietrasiewicz wrote:
>> Use the ddc pointer provided by the generic connector.
>>
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
>> ---
>>   drivers/gpu/drm/tilcdc/tilcdc_tfp410.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_tfp410.c b/drivers/gpu/drm/tilcdc/tilcdc_tfp410.c
>> index 62d014c20988..c373edb95666 100644
>> --- a/drivers/gpu/drm/tilcdc/tilcdc_tfp410.c
>> +++ b/drivers/gpu/drm/tilcdc/tilcdc_tfp410.c
>> @@ -219,6 +219,7 @@ static struct drm_connector *tfp410_connector_create(struct drm_device *dev,
>>   	tfp410_connector->mod = mod;
>>   
>>   	connector = &tfp410_connector->base;
>> +	connector->ddc = mod->i2c;
>>   
>>   	drm_connector_init(dev, connector, &tfp410_connector_funcs,
>>   			DRM_MODE_CONNECTOR_DVID);
> 
> When reading this code, it looks strange that we set connector->ddc
> *before* the call to init the connector.
> One could risk that drm_connector_init() used memset(..) to clear all
> fields or so, and it would break this order.

I verified the code of drm_connector_init() and cannot find any memset()
invocations there. What is your actual concern?

Andrzej