linux-kernel - Re: [PATCH v7 03/13] hwmon: pwm-fan: Use 64-bit division macros for period and duty cycle

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Message-ID: <ba406ba4-8a2d-481d-11ab-9e282923e68c@roeck-us.net>
Date:   Tue, 10 Mar 2020 15:57:34 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Guru Das Srinagesh <gurus@...eaurora.org>
Cc:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        linux-kernel@...r.kernel.org, Kamil Debski <kamil@...as.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Jean Delvare <jdelvare@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v7 03/13] hwmon: pwm-fan: Use 64-bit division macros for
 period and duty cycle

On 3/10/20 3:24 PM, Guru Das Srinagesh wrote:
> On Tue, Mar 10, 2020 at 08:05:58AM -0700, Guenter Roeck wrote:
>> I don't see support in the LED subsystem to utilize the PWM framework directly
>> for blinking. Plus, you say yourself that it isn't a _real_ use case, just a
>> theoretic one.
> 
> An example use case is a mobile phone OEM that wishes to set a period of
> 5 seconds or more for, say, a low battery slow blinking indication - currently
> this is not possible. The PWM framework not having direct support for
> blinking should not be a concern if the PWM peripheral being controlled
> supports it via register writes.
> 
>> Either case, the reason / use case for this series should be explained
>> in the summary patch. That is what it is for. That case is not made.
> 
> Will upload a new patchset adding more details in the summary patch.
> 

Well, let's assume that this is a real use case.

Please also add information about alternatives considered, such as keeping
the second-part of the period in a separate variable.

Guenter