linux-kernel - Re: [PATCH 3/3] drm/panel: Add panel driver for the Mantix MLAF057WE51-X DSI panel

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Message-ID: <20200815162558.GA2744@bogon.m.sigxcpu.org>
Date:   Sat, 15 Aug 2020 18:25:58 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        Daniel Palmer <daniel@...f.com>,
        Lubomir Rintel <lkundrak@...sk>,
        Mark Brown <broonie@...nel.org>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        allen <allen.chen@....com.tw>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] drm/panel: Add panel driver for the Mantix
 MLAF057WE51-X DSI panel

Hi,
On Sat, Aug 15, 2020 at 12:46:51PM +0200, Sam Ravnborg wrote:
> On Sat, Aug 15, 2020 at 12:40:22PM +0200, Guido Günther wrote:
> > Hi Sam,
> > On Sat, Aug 15, 2020 at 12:02:30PM +0200, Sam Ravnborg wrote:
> > > Hi Guido.
> > > 
> > > > +static int mantix_probe(struct mipi_dsi_device *dsi)
> > > > +{
> > > > +	struct device *dev = &dsi->dev;
> > > > +	struct mantix *ctx;
> > > > +	int ret;
> > > > +
> > > > +	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> > > > +	if (!ctx)
> > > > +		return -ENOMEM;
> > > > +
> > > > +	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> > > > +	if (IS_ERR(ctx->reset_gpio)) {
> > > > +		DRM_DEV_ERROR(dev, "cannot get reset gpio\n");
> > > > +		return PTR_ERR(ctx->reset_gpio);
> > > > +	}
> > > > +
> > > > +	mipi_dsi_set_drvdata(dsi, ctx);
> > > > +	ctx->dev = dev;
> > > > +
> > > > +	dsi->lanes = 4;
> > > > +	dsi->format = MIPI_DSI_FMT_RGB888;
> > > > +	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
> > > > +		MIPI_DSI_MODE_VIDEO_BURST | MIPI_DSI_MODE_VIDEO_SYNC_PULSE;
> > > > +
> > > > +	ctx->avdd = devm_regulator_get(dev, "avdd");
> > > > +	if (IS_ERR(ctx->avdd)) {
> > > > +		ret = PTR_ERR(ctx->avdd);
> > > > +		if (ret != -EPROBE_DEFER)
> > > > +			DRM_DEV_ERROR(dev,
> > > > +				      "Failed to request avdd regulator: %d\n",
> > > > +				      ret);
> > > > +		return ret;
> > > > +	}
> > > 
> > > Consider to use the recently added dev_err_probe() here and below.
> > > Note: Not part of drm-misc-next yet - but hopefully after -rc1
> > > when a backmerge is done.
> > 
> > In fact I did decided against it since i was told that missing dev_* and
> > DRM_* logging shouldn't be done. So is that o.k. nowadays?
> s/missing/mixing/
> 
> I often request that logging is consistent - so I recognize the
> argument.
> 
> For panel/* I have not made up my mind what I think is the best
> approach. The DRM_DEV_* and DRM_* logging do not add much value.
> So I have been tempted several times to convert all logging in
> panel/ to dev_* and pr_* (when no struct device * is available).
> That would also avoid that we mix up logging.
> 
> We have drm_* logging - but they require a valid drm_device * which we
> do not have in the the panel drivers. So they are ruled out here.
> 
> Do you have any opinions/comments on this?

I think for panel drivers DRM_* does not give any bonus so moving to
{dev,pr}_* sounds good. I just wonder if other drm parts don't need
`dev_drm_err_probe()` (or similar) anyway. But then maybe dyn_debug
is enough nowadays to not need DRM_DEV_DEBUG_* either?
Cheers,
 -- Guido

> 
> 	Sam
>