From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Stein Subject: Re: [PATCH] gpio: mcp23s08: Add option to configure pullups. Date: Mon, 24 Oct 2016 08:13:54 +0200 Message-ID: <11644726.TmP4uu3h4l@ws-stein> References: <1477062035-30825-1-git-send-email-enric.balletbo@collabora.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-gpio-owner@vger.kernel.org To: Linus Walleij Cc: Enric Balletbo i Serra , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-gpio@vger.kernel.org" , Rob Herring List-Id: devicetree@vger.kernel.org On Monday 24 October 2016 02:53:31, Linus Walleij wrote: > On Fri, Oct 21, 2016 at 5:00 PM, Enric Balletbo i Serra > > 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 > > 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