From: Mark Brown <broonie@kernel.org>
To: Sander Vanheule <sander@svanheule.net>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
Pavel Machek <pavel@ucw.cz>, Rob Herring <robh+dt@kernel.org>,
Lee Jones <lee.jones@linaro.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Michael Walle <michael@walle.cc>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Linux LED Subsystem <linux-leds@vger.kernel.org>,
devicetree <devicetree@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Andrew Lunn <andrew@lunn.ch>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 2/8] gpio: regmap: Add quirk for aliased data registers
Date: Thu, 8 Jul 2021 15:23:06 +0100 [thread overview]
Message-ID: <20210708142306.GA4106@sirena.org.uk> (raw)
In-Reply-To: <dee12a4f5dc1a37feb14e20074cf365dbb86bc05.camel@svanheule.net>
[-- Attachment #1: Type: text/plain, Size: 1821 bytes --]
On Wed, Jul 07, 2021 at 10:53:19PM +0200, Sander Vanheule wrote:
> I've made an attempt at implementing a "regmap_aliased()", similar to
> "regmap_volatile()". However, this meant I had to make _regmap_read() aware of
> wether the read- or write-alias was being read (from cache), touching some parts
> of the regmap code I'm not using myself. Furthermore, this "aliased" property
> isn't really perpendicular to "volatile", since writes should never be volatile,
> and non-volatile reads don't make much sense (to me) on a read-only register.
As far as the abstractions in regmap are concerned these registers are
volatile, that's currently how regmap undertands registers where
readback won't give you the last written value. Trying to convince the
framework to handle these registers as anything other than volatile is
going to of need be an invasive change.
> If a regmap_field could overwrite the specifiers of it's parent register, I
> think this may provide quite a natural solution to the aliasing problem: just
> create two regmap_field defintions. One definition would be 'write-only' (and
> cached for RMW), the other 'volatile read-only'. All regmap_fields could still
> rely on a single cached register value, I think. I didn't try to implement this
> though, so maybe I'm missing some behaviour that would disqualify this solution.
> Would you think this could be an acceptable way to move forward here?
This feels like a painful and potentially high overhead approach to
things - at the minute fields are layered on top of registers and are
totally invisible at the register level, pulling the two together would
touch a lot of places and make things tense, especially if we ended up
with two different fields aliasing each other. I'd need to see code but
it feels like a difficult approach to take.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2021-07-08 14:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-12 21:12 [PATCH v5 0/8] RTL8231 GPIO expander support Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 1/8] regmap: Support atomic forced uncached reads Sander Vanheule
2021-06-12 21:23 ` Andy Shevchenko
2021-06-14 10:33 ` Mark Brown
2021-06-12 21:12 ` [PATCH v5 2/8] gpio: regmap: Add quirk for aliased data registers Sander Vanheule
2021-06-12 21:29 ` Andy Shevchenko
2021-07-07 20:53 ` Sander Vanheule
2021-07-08 14:23 ` Mark Brown [this message]
2021-06-12 21:12 ` [PATCH v5 3/8] dt-bindings: leds: Binding for RTL8231 scan matrix Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 4/8] dt-bindings: mfd: Binding for RTL8231 Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 5/8] mfd: Add RTL8231 core device Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 6/8] pinctrl: Add RTL8231 pin control and GPIO support Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 7/8] leds: Add support for RTL8231 LED scan matrix Sander Vanheule
2021-06-12 21:12 ` [PATCH v5 8/8] MAINTAINERS: Add RTL8231 MFD driver Sander Vanheule
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210708142306.GA4106@sirena.org.uk \
--to=broonie@kernel.org \
--cc=andrew@lunn.ch \
--cc=andy.shevchenko@gmail.com \
--cc=bgolaszewski@baylibre.com \
--cc=devicetree@vger.kernel.org \
--cc=gregkh@linuxfoundation.org \
--cc=lee.jones@linaro.org \
--cc=linus.walleij@linaro.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-leds@vger.kernel.org \
--cc=michael@walle.cc \
--cc=pavel@ucw.cz \
--cc=rafael@kernel.org \
--cc=robh+dt@kernel.org \
--cc=sander@svanheule.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.