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Date: Fri, 6 Apr 2012 16:17:20 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Thomas Abraham <thomas.abraham@...aro.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
rpurdie@...ys.net, florianSchandinat@....de,
devicetree-discuss@...ts.ozlabs.org, linux-fbdev@...r.kernel.org,
linux-samsung-soc@...r.kernel.org, grant.likely@...retlab.ca,
rob.herring@...xeda.com, kgene.kim@...sung.com,
jg1.han@...sung.com, broonie@...nsource.wolfsonmicro.com,
kyungmin.park@...sung.com, augulis.darius@...il.com,
ben-linux@...ff.org, lars@...afoo.de, patches@...aro.org
Subject: Re: [PATCH v3 1/2] backlight: lcd: add driver for raster-type lcd's
with gpio controlled panel reset
> Cc: rpurdie@...ys.net, florianSchandinat@....de, devicetree-discuss@...ts.ozlabs.org, linux-fbdev@...r.kernel.org, linux-samsung-soc@...r.kernel.org, grant.likely@...retlab.ca, rob.herring@...xeda.com, kgene.kim@...sung.com, jg1.han@...sung.com, broonie@...nsource.wolfsonmicro.com, kyungmin.park@...sung.com, augulis.darius@...il.com, ben-linux@...ff.org, lars@...afoo.de, patches@...aro.org
Poor me. When someone sends a patch like this, I need to go and hunt
down everyone's real names to nicely add them to the changelog's Cc:
list. I prefer that you do this ;)
You can add Cc:'s to the changelog yourself, of course. Often that
works out better than having me try to work out who might be
interested in the patch.
On Mon, 26 Mar 2012 14:16:39 +0530
Thomas Abraham <thomas.abraham@...aro.org> wrote:
> Add a lcd panel driver for simple raster-type lcd's which uses a gpio
> controlled panel reset. The driver controls the nRESET line of the panel
> using a gpio connected from the host system. The Vcc supply to the panel
> is (optionally) controlled using a voltage regulator. This driver excludes
> support for lcd panels that use a serial command interface or direct
> memory mapped IO interface.
>
>
> ...
>
> +struct lcd_pwrctrl {
> + struct device *dev;
> + struct lcd_device *lcd;
> + struct lcd_pwrctrl_data *pdata;
> + struct regulator *regulator;
> + unsigned int power;
> + bool suspended;
> + bool pwr_en;
Generally kernel code will avoid these unpronounceable abbreviations.
So we do
pwr -> power
en -> enable
ctrl -> control
etc. It results in longer identifiers, but the code is more readable
and, more importantly, more *rememberable*.
> +};
> +
> +static int lcd_pwrctrl_get_power(struct lcd_device *lcd)
> +{
> + struct lcd_pwrctrl *lp = lcd_get_data(lcd);
> + return lp->power;
> +}
> +
> +static int lcd_pwrctrl_set_power(struct lcd_device *lcd, int power)
See, shouldn't that have been lcd_pwrctrl_set_pwr?
If we avoid the abbreviations, such issues do not arise.
> +{
> + struct lcd_pwrctrl *lp = lcd_get_data(lcd);
> + struct lcd_pwrctrl_data *pd = lp->pdata;
> + bool lcd_enable;
> + int lcd_reset, ret = 0;
> +
> + lcd_enable = (power == FB_BLANK_POWERDOWN || lp->suspended) ? 0 : 1;
This isn't how to use `bool'. We can use
lcd_enable = (power == FB_BLANK_POWERDOWN) || lp->suspended;
> + lcd_reset = (pd->invert) ? !lcd_enable : lcd_enable;
> +
> + if (lp->pwr_en == lcd_enable)
> + return 0;
> +
> + if (!IS_ERR_OR_NULL(lp->regulator)) {
> + if (lcd_enable) {
> + if (regulator_enable(lp->regulator)) {
> + dev_info(lp->dev, "regulator enable failed\n");
> + ret = -EPERM;
> + }
> + } else {
> + if (regulator_disable(lp->regulator)) {
> + dev_info(lp->dev, "regulator disable failed\n");
> + ret = -EPERM;
> + }
> + }
> + }
> +
> + gpio_direction_output(lp->pdata->gpio, lcd_reset);
> + lp->power = power;
> + lp->pwr_en = lcd_enable;
Again, this could have been any of
lp->[power|pwr] = [power|pwr];
lp->[power|pwr]_[en|enable] = lcd_[en|enable];
zillions of combinations! If we just avoid the abbreviations, there is
only one combination.
> + return ret;
> +}
> +
>
> ...
>
> +static int __devinit lcd_pwrctrl_probe(struct platform_device *pdev)
> +{
> + struct lcd_pwrctrl *lp;
> + struct lcd_pwrctrl_data *pdata = pdev->dev.platform_data;
> + struct device *dev = &pdev->dev;
> + int err;
> +
> +#ifdef CONFIG_OF
> + if (dev->of_node) {
> + pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
> + if (!pdata) {
> + dev_err(dev, "memory allocation for pdata failed\n");
> + return -ENOMEM;
> + }
> + lcd_pwrctrl_parse_dt(dev, pdata);
> + }
> +#endif
> +
> + if (!pdata) {
> + dev_err(dev, "platform data not available\n");
> + return -EINVAL;
> + }
> +
> + lp = devm_kzalloc(dev, sizeof(struct lcd_pwrctrl), GFP_KERNEL);
Nit: I prefer sizeof(*lp) here, so I don't have to scroll back and
check the type of lp.
> + if (!lp) {
> + dev_err(dev, "memory allocation failed for private data\n");
> + return -ENOMEM;
> + }
> +
> + err = gpio_request(pdata->gpio, "LCD-nRESET");
> + if (err) {
> + dev_err(dev, "gpio [%d] request failed\n", pdata->gpio);
> + return err;
> + }
> +
>
> ...
>
The code looks OK to me, but I do think the naming decisions should be
revisited, please.
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