From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
To: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: "Geert Uytterhoeven" <geert@linux-m68k.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Miquèl Raynal" <miquel.raynal@free-electrons.com>,
"Nadav Haklai" <nadavh@marvell.com>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
"Antoine Ténart" <antoine.tenart@free-electrons.com>,
"Gregory CLEMENT" <gregory.clement@free-electrons.com>,
"Timur Tabi" <timur@codeaurora.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: linux-next regression caused by "gpiolib: request the gpio before querying its direction"
Date: Thu, 31 Aug 2017 11:39:35 +0200 [thread overview]
Message-ID: <20170831113935.38028ff8@windsurf.lan> (raw)
In-Reply-To: <20170831092211.GP20805@n2100.armlinux.org.uk>
Hello,
On Thu, 31 Aug 2017 10:22:12 +0100, Russell King - ARM Linux wrote:
> What about hardware which you can configure for some alternate function
> but still monitor the pin via GPIO, even though it's not mux'd as GPIO.
>
> For instance, you may have a timer block which can capture on both
> edges of an external event signal, which needs the pin to be muxed for
> that function. However, you need to read the state of the pin, and
> that is only available through GPIO. Muxing the pin to be a GPIO just
> because someone requests the GPIO is, imho, ill thought-out and breaks
> some use cases.
>
> IMHO, the pinmux settings should always be specified in DT, and that's
> what we should be using everywhere, not doing broken backdoor games like
> "the gpio is being requested, it's obvious that we want this pin to be
> a gpio" - that really doesn't follow.
Agreed.
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
WARNING: multiple messages have this Message-ID (diff)
From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni)
To: linux-arm-kernel@lists.infradead.org
Subject: linux-next regression caused by "gpiolib: request the gpio before querying its direction"
Date: Thu, 31 Aug 2017 11:39:35 +0200 [thread overview]
Message-ID: <20170831113935.38028ff8@windsurf.lan> (raw)
In-Reply-To: <20170831092211.GP20805@n2100.armlinux.org.uk>
Hello,
On Thu, 31 Aug 2017 10:22:12 +0100, Russell King - ARM Linux wrote:
> What about hardware which you can configure for some alternate function
> but still monitor the pin via GPIO, even though it's not mux'd as GPIO.
>
> For instance, you may have a timer block which can capture on both
> edges of an external event signal, which needs the pin to be muxed for
> that function. However, you need to read the state of the pin, and
> that is only available through GPIO. Muxing the pin to be a GPIO just
> because someone requests the GPIO is, imho, ill thought-out and breaks
> some use cases.
>
> IMHO, the pinmux settings should always be specified in DT, and that's
> what we should be using everywhere, not doing broken backdoor games like
> "the gpio is being requested, it's obvious that we want this pin to be
> a gpio" - that really doesn't follow.
Agreed.
Thomas
--
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
next prev parent reply other threads:[~2017-08-31 9:57 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-30 9:24 linux-next regression caused by "gpiolib: request the gpio before querying its direction" Thomas Petazzoni
2017-08-30 9:24 ` Thomas Petazzoni
2017-08-30 12:31 ` Timur Tabi
2017-08-30 12:31 ` Timur Tabi
2017-08-30 13:59 ` Gregory CLEMENT
2017-08-30 13:59 ` Gregory CLEMENT
2017-08-30 14:17 ` Thomas Petazzoni
2017-08-30 14:17 ` Thomas Petazzoni
2017-08-30 14:22 ` Timur Tabi
2017-08-30 14:22 ` Timur Tabi
2017-08-30 14:32 ` Thomas Petazzoni
2017-08-30 14:32 ` Thomas Petazzoni
2017-08-30 16:24 ` jmondi
2017-08-30 16:24 ` jmondi
2017-08-30 19:38 ` Geert Uytterhoeven
2017-08-30 19:38 ` Geert Uytterhoeven
2017-08-31 7:08 ` Linus Walleij
2017-08-31 7:08 ` Linus Walleij
2017-08-31 7:18 ` Thomas Petazzoni
2017-08-31 7:18 ` Thomas Petazzoni
2017-08-31 7:30 ` Geert Uytterhoeven
2017-08-31 7:30 ` Geert Uytterhoeven
2017-08-31 9:22 ` Russell King - ARM Linux
2017-08-31 9:22 ` Russell King - ARM Linux
2017-08-31 9:39 ` Thomas Petazzoni [this message]
2017-08-31 9:39 ` Thomas Petazzoni
2017-08-31 18:39 ` Timur Tabi
2017-08-31 18:39 ` Timur Tabi
2017-08-31 9:50 ` Geert Uytterhoeven
2017-08-31 9:50 ` Geert Uytterhoeven
2017-08-31 13:05 ` Timur Tabi
2017-08-31 13:05 ` Timur Tabi
2017-08-31 10:08 ` Maxime Ripard
2017-08-31 10:08 ` Maxime Ripard
2017-08-31 7:04 ` Linus Walleij
2017-08-31 7:04 ` Linus Walleij
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