From: Alexander Stein <alexander.stein@systec-electronic.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH] gpio: mcp23s08: Add option to configure pullups.
Date: Mon, 24 Oct 2016 08:13:54 +0200 [thread overview]
Message-ID: <11644726.TmP4uu3h4l@ws-stein> (raw)
In-Reply-To: <CACRpkdY15Hv_ydHyOXRM6G0ewVTHkVa1w3Z89AdvSDR=eyi7sQ@mail.gmail.com>
On Monday 24 October 2016 02:53:31, Linus Walleij wrote:
> On Fri, Oct 21, 2016 at 5:00 PM, Enric Balletbo i Serra
>
> <enric.balletbo@collabora.com> wrote:
> > Default is without pullups, but if property is specified in DT and the bit
> > is set, set a pullup on GPIO-n.
> >
> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>
> I don't generally like this.
>
> In device tree it is the consumer that specifies how the line is used,
> not the producer (gpiochip).
>
> We currently only specify polarity, open drain and open source
> for consumers though.
>
> And the entire pin control system came into being *exactly* because
> Grant didn't like me adding these things to the GPIO drivers.
>
> So how many other things does the MCP support? Drive strength?
> Schmitt trigger? Is there a datasheet?
Some unsupported features (AFAIK):
* Input polarity (IPOL register)
* open-drain interrupt pin
* pullup on pins (proposed patch)
Datasheet is here: http://ww1.microchip.com/downloads/en/DeviceDoc/21919e.pdf
Best regards,
Alexander
next prev parent reply other threads:[~2016-10-24 6:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-21 15:00 [PATCH] gpio: mcp23s08: Add option to configure pullups Enric Balletbo i Serra
2016-10-24 0:53 ` Linus Walleij
2016-10-24 6:13 ` Alexander Stein [this message]
2016-10-26 9:59 ` Enric Balletbo Serra
2016-10-27 12:22 ` Linus Walleij
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