linux-kernel - Re: [PATCH] backlight: add regulator support for platform

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 5 Dec 2011 16:06:17 +0530
From:	Thomas Abraham <thomas.abraham@...aro.org>
To:	Kyungmin Park <kmpark@...radead.org>
Cc:	rpurdie@...ys.net, ben-linux@...ff.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org, kgene.kim@...sung.com,
	patches@...aro.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Rajendra Nayak <rnayak@...com>
Subject: Re: [PATCH] backlight: add regulator support for platform_lcd driver

Dear Mr. Park,

On 5 December 2011 15:40, Kyungmin Park <kmpark@...radead.org> wrote:
[...]

>> +     /*
>> +      * If power to lcd and/or lcd interface is controlled using a regulator,
>> +      * enable or disable the regulator based in the power setting.
>> +      */
>> +     lcd_regulator = regulator_get(plcd->us, "vcc_lcd");
>> +     if (IS_ERR(lcd_regulator)) {
>> +             dev_info(plcd->us, "could not get regulator\n");
>> +             goto set_power;
>> +     }
>
> Recent regulator discussion. it should be failed instead fall through
> gracefully.

Ok. But in this case, there could be boards that do not use a
regulator for the lcd/display interface. Is it mandatory for fail if
regulator is not found. Sorry, I have not read through the regulator
discussion.

>> +
>> +     if (lcd_power) {
>> +             if (plcd->pdata->min_uV || plcd->pdata->max_uV)
>> +                     if (regulator_set_voltage(lcd_regulator,
>> +                             plcd->pdata->min_uV, plcd->pdata->max_uV))
>> +                             dev_info(plcd->us,
>> +                                     "regulator voltage set failed\n");
> Are there case to change the voltage? Doesn't it easy to set the
> voltage at board file? I mean don't need to setup at drivers?

The constraint 'apply_uV' cannot be expressed with a device tree. So
there has be a mechanism to set the required output voltage for a
regulator.

In case of platform-lcd driver, the power source should be turned off
to the lcd/interfaces until the display controller driver is enabled.
Powering on the lcd/interfaces at boot time by default would not be
ideal.

Thanks for your review and comments.

Regards,
Thomas.

>
> Thank you,
> Kyungmin Park

[...]
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/