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From: Pavel Machek <pavel@ucw.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Dan Murphy <dmurphy@ti.com>,
	linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND PATCH v17 00/17] Multi Color LED Framework
Date: Wed, 26 Feb 2020 13:59:03 +0100	[thread overview]
Message-ID: <20200226125903.GA2800@duo.ucw.cz> (raw)
In-Reply-To: <be76fdac-9d32-b9b2-c01d-3aa315b14463@gmail.com>

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Hi!

> > The fact that it changes API makes it important to get it right, and
> > hard/impossible to fix it once it is merged... and I don't think this
> > is the right interface (sorry).
> > 
> > In particular, I don't think having directory per channel is a good
> > idea. It makes atomic updates impossible (minor), 
> 
> It is possible via brightness file, although it will need first writing
> intensity files, which only will cache colors, and actual write to hw
> occurs on write to brightness file. This has been discussed dozen of
> times throughout last year, and you even proposed the formula for
> calculating per-color-subled brightness basing on global brightness and
> intensity set for each color.

You are right, it is possible to make updates atomic with right kind
of latching (which is quite confusing).

> > but will also
> > increase memory consuption (to a point where led-per-channel might
> > be cheaper), and will make userspace do 3x ammount of syscalls in the
> > common case.
> > 
> > And we can do better; sysfs files with arrays are okay. So I'd like to
> > see
> 
> Let's first achieve broader consensus on this statement before we
> move forward with such design. Sysfs maintainer seems to be the best
> person to consult at first.

This is actually documented:

Documentation/filesystems/sysfs.txt

<quote>
Attributes should be ASCII text files, preferably with only one value
per file. It is noted that it may not be efficient to contain only one
value per file, so it is socially acceptable to express an array of
values of the same type.

Mixing types, expressing multiple lines of data, and doing fancy
formatting of data is heavily frowned upon. Doing these things may get
you publicly humiliated and your code rewritten without notice.
</quote>

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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  parent reply	other threads:[~2020-02-26 12:59 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-27 15:00 [RESEND PATCH v17 00/17] Multi Color LED Framework Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 01/17] dt-bindings: leds: Add multicolor ID to the color ID list Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 02/17] " Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 03/17] leds: multicolor: Introduce a multicolor class definition Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 04/17] dt: bindings: lp50xx: Introduce the lp50xx family of RGB drivers Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 05/17] leds: lp50xx: Add the LP50XX family of the RGB LED driver Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 06/17] dt: bindings: lp55xx: Be consistent in the document with LED acronym Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 07/17] dt: bindings: lp55xx: Update binding for Multicolor Framework Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 08/17] ARM: dts: n900: Add reg property to the LP5523 channel node Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 09/17] ARM: dts: imx6dl-yapp4: Add reg property to the lp5562 " Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 10/17] ARM: dts: ste-href: Add reg property to the LP5521 channel nodes Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 11/17] leds: lp55xx: Convert LED class registration to devm_* Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 12/17] leds: lp55xx: Add multicolor framework support to lp55xx Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 13/17] leds: lp5523: Update the lp5523 code to add multicolor brightness function Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 14/17] leds: lp5521: Add multicolor framework multicolor brightness support Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 15/17] leds: lp55xx: Fix checkpatch file permissions issues Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 16/17] leds: lp5523: Fix checkpatch issues in the code Dan Murphy
2020-01-27 15:00 ` [RESEND PATCH v17 17/17] dt: bindings: Update lp55xx binding to recommended LED naming Dan Murphy
2020-02-12 13:09 ` [RESEND PATCH v17 00/17] Multi Color LED Framework Dan Murphy
2020-02-25 10:19   ` Pavel Machek
2020-02-25 22:17     ` Jacek Anaszewski
2020-02-25 22:44       ` Dan Murphy
2020-02-26 12:59       ` Pavel Machek [this message]
2020-02-26 20:45         ` Jacek Anaszewski
2020-02-26 22:10           ` Dan Murphy
2020-02-27 10:58           ` Pavel Machek
2020-02-27 12:43             ` Greg KH
2020-02-27 13:07               ` Dan Murphy
2020-02-27 13:29                 ` Dan Murphy
2020-02-27 21:22                 ` Jacek Anaszewski
2020-02-28  7:42                   ` Greg KH
2020-02-28  9:34                     ` Pavel Machek
2020-02-28 12:30                     ` Dan Murphy
2020-02-28  9:39                   ` Pavel Machek

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