linux-kernel - Re: [PATCH v3 2/3] drm: bridge: Add thc63lvd1024 LVDS decoder driver

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Message-ID: <20180314180438.GD16424@w540>
Date:   Wed, 14 Mar 2018 19:04:38 +0100
From:   jacopo mondi <jacopo@...ndi.org>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     Jacopo Mondi <jacopo+renesas@...ndi.org>, architt@...eaurora.org,
        a.hajda@...sung.com, Laurent.pinchart@...asonboard.com,
        airlied@...ux.ie, horms@...ge.net.au, magnus.damm@...il.com,
        geert@...ux-m68k.org, niklas.soderlund@...natech.se,
        robh+dt@...nel.org, mark.rutland@....com,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] drm: bridge: Add thc63lvd1024 LVDS decoder driver

Hi Sergei,
   thanks for review

On Wed, Mar 14, 2018 at 08:09:52PM +0300, Sergei Shtylyov wrote:
> On 03/13/2018 05:30 PM, Jacopo Mondi wrote:
>
> > Add DRM bridge driver for Thine THC63LVD1024 LVDS to digital parallel
> > output decoder.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> [...]
> > diff --git a/drivers/gpu/drm/bridge/thc63lvd1024.c b/drivers/gpu/drm/bridge/thc63lvd1024.c
> > new file mode 100644
> > index 0000000..4b059c0
> > --- /dev/null
> > +++ b/drivers/gpu/drm/bridge/thc63lvd1024.c
> > @@ -0,0 +1,241 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * THC63LVD1024 LVDS to parallel data DRM bridge driver.
> > + *
> > + * Copyright (C) 2018 Jacopo Mondi <jacopo+renesas@...ndi.org>
> > + */
> > +
> > +#include <drm/drmP.h>
> > +#include <drm/drm_bridge.h>
> > +#include <drm/drm_panel.h>
> > +
> > +#include <linux/gpio/consumer.h>
> > +#include <linux/of_graph.h>
> > +#include <linux/regulator/consumer.h>
> > +
> > +static const char * const thc63_reg_names[] = {
> > +	"vcc", "lvcc", "pvcc", "cvcc", };
>
>    Your bracing style is pretty strange -- neither here nor there. Please place };
> on the next line...

Yeah, I had doubt about this.. The most common style I found around is

static const char * const foo[] = {
        "bar",
        "baz",
        "...",
};

But seems really too many lines for a bunch of 4 character strings...

>
> [...]
> > +static void thc63_enable(struct drm_bridge *bridge)
> > +{
> > +	struct thc63_dev *thc63 = to_thc63(bridge);
> > +	struct regulator *vcc;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(thc63->vccs); i++) {
> > +		vcc = thc63->vccs[i];
> > +		if (vcc) {
> > +			ret = regulator_enable(vcc);
> > +			if (ret)
>
>    You hardly need this variable, could do a call right in this *if*.
>
> [...]
> > +error_vcc_enable:
> > +	dev_err(thc63->dev, "Failed to enable regulator %u\n", i);
> > +}
> > +
>
>    Why not do this instead of *goto* before?

Well, goto breaks the loop, if I only print out the error message, the
enable sequence will go on and enable the other regulators.

I can print out and break, but I don't see that much benefit

One thing I could do instead, is not only print out the error message,
but disable the already enabled regulators if one fails to start.

>
> > +static void thc63_disable(struct drm_bridge *bridge)
> > +{
> > +	struct thc63_dev *thc63 = to_thc63(bridge);
> > +	struct regulator *vcc;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(thc63->vccs); i++) {
> > +		vcc = thc63->vccs[i];
> > +		if (vcc) {
> > +			ret = regulator_disable(vcc);
> > +			if (ret)
>
>    Again, no need for 'ret' whatsoever...
>
> > +				goto error_vcc_disable;
> > +		}
> > +	}
> > +
> > +	if (thc63->pwdn)
> > +		gpiod_set_value(thc63->pwdn, 1);
> > +
> > +	if (thc63->oe)
> > +		gpiod_set_value(thc63->oe, 0);
> > +
> > +	return;
> > +
> > +error_vcc_disable:
> > +	dev_err(thc63->dev, "Failed to disable regulator %u\n", i);
>
>    Again, why not do it instead of *goto*?

ditto

>
> [...]
> > +static int thc63_gpio_init(struct thc63_dev *thc63)
> > +{
> > +	thc63->pwdn = devm_gpiod_get_optional(thc63->dev, "pwdn",
> > +					      GPIOD_OUT_LOW);
> > +	if (IS_ERR(thc63->pwdn)) {
> > +		dev_err(thc63->dev, "Unable to get GPIO \"pwdn\"\n");
>
>    "pwdn-gpios" maybe?
>
> > +		return PTR_ERR(thc63->pwdn);
> > +	}
> > +
> > +	thc63->oe = devm_gpiod_get_optional(thc63->dev, "oe", GPIOD_OUT_LOW);
> > +	if (IS_ERR(thc63->oe)) {
> > +		dev_err(thc63->dev, "Unable to get GPIO \"oe\"\n");
>
>    "oe-gpios" maybe?

Are you referring to the error message? I can change this, but again, I
see no standards around.

Thanks
   j

>
> [...]
>
> MBR, Sergei

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