Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752941Ab3H0KkE (ORCPT ); Tue, 27 Aug 2013 06:40:04 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:38719 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752194Ab3H0KkB (ORCPT ); Tue, 27 Aug 2013 06:40:01 -0400 Date: Tue, 27 Aug 2013 11:39:49 +0100 From: Mark Rutland To: Tomasz Figa Cc: Laurent Pinchart , Laurent Pinchart , "linux-gpio@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , Linus Walleij , "swarren@wwwdotorg.org" , "ian.campbell@citrix.com" , Pawel Moll , "galak@codeaurora.org" , "rob.herring@calxeda.com" Subject: Re: [PATCH v2 3/3] gpio: pcf857x: Add OF support Message-ID: <20130827103949.GF19893@e106331-lin.cambridge.arm.com> References: <1376953494-9684-1-git-send-email-laurent.pinchart+renesas@ideasonboard.com> <5465986.lNHQvRvp7j@flatron> <1688346.YLZnUtEaXr@avalon> <2417846.CRj8QejgZy@flatron> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2417846.CRj8QejgZy@flatron> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7024 Lines: 179 On Sat, Aug 24, 2013 at 03:13:11PM +0100, Tomasz Figa wrote: > On Saturday 24 of August 2013 02:54:07 Laurent Pinchart wrote: > > Hi Tomasz, > > > > Thank you for the review. > > > > On Saturday 24 August 2013 02:41:59 Tomasz Figa wrote: > > > On Tuesday 20 of August 2013 01:04:54 Laurent Pinchart wrote: > > > > Add DT bindings for the pcf857x-compatible chips and parse the > > > > device > > > > tree node in the driver. > > > > > > > > Signed-off-by: Laurent Pinchart > > > > --- > > > > > > > > .../devicetree/bindings/gpio/gpio-pcf857x.txt | 71 > > > > +++++++++++++++++ drivers/gpio/gpio-pcf857x.c > > > > | 57 ++++++++++++++--- 2 files changed, 119 insertions(+), 9 > > > > deletions(-) > > > > > > > > create mode 100644 > > > > > > > > Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt > > > > > > > > diff --git a/Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt > > > > b/Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt new file > > > > mode > > > > 100644 > > > > index 0000000..df94462 > > > > --- /dev/null > > > > +++ b/Documentation/devicetree/bindings/gpio/gpio-pcf857x.txt > > > > @@ -0,0 +1,71 @@ > > > > [snip] > > > > > > + - pins-initial-state: Bitmask that specifies the initial state of > > > > + each pin. When a bit is set to zero, the corresponding pin will > > > > be > > > > + initialized to the input (pulled-up) state. When the bit is > > > > set to + one, the pin will be initialized the the low-level > > > > output state. If + the property is not specified all pins will > > > > be initialized to the + input state. > > > > > > Hmm, do you actually need to know whether those pins are outputs or > > > inputs before they get used for first time? I believe any driver > > > using GPIO will call gpio_direction_{in,out}put() before it starts > > > using the pin, which will initialize the pin to a known state. > > > > > > What I'd suggest is making the driver handle this by having a bit mask > > > that marks states of pins as defined and flagging all pins as > > > undefined by default. Then any call to gpio_direction_output() or > > > _input() would mark it as defined and direction of the pin could be > > > stored in internal driver structures. > > > > The problem is that all pins are controlled through a single I2C write. > > Setting the direction of a pin will set the direction of all other pins. > > I thus need to know what the initial settings are to avoid glitches. I guess it's not possible to read the initial state from the hardware? > > Oh, that's a funny hardware, isn't it? :) > > Well, I guess it can't be helped then. Sorry for the noise. > > > > > + The I/O expander can detect input state changes, and thus > > > > optionally > > > > + act as an interrupt controller. When interrupts support is > > > > desired > > > > > > I don't like this statement. Device tree should represent what the > > > device allows you to do, not what you want the device to do. > > > > > > My opinion on this is that if the chip supports interrupts then it > > > should always be an interrupt-controller (unless its interrupt pin is > > > not wired on the board, but this still conforms to what I wrote > > > above). > > > > I agree. What about the following text then ? > > > > The I/O expander can detect input state changes, and thus optionally act > > as an interrupt controller. When the expander interrupt pin is > > connected all the following properties must be set. For more > > information please see the interrupt controller device tree bindings > > documentation available at > > Documentation/devicetree/bindings/interrupt-controller/interrupts.txt. > > Sounds good. > > > > > diff --git a/drivers/gpio/gpio-pcf857x.c > > > > b/drivers/gpio/gpio-pcf857x.c > > > > index 070e81f..50a90f1 100644 > > > > --- a/drivers/gpio/gpio-pcf857x.c > > > > +++ b/drivers/gpio/gpio-pcf857x.c > > > > [snip] > > > > > > @@ -50,6 +52,27 @@ static const struct i2c_device_id pcf857x_id[] = > > > > { > > > > > > > > }; > > > > MODULE_DEVICE_TABLE(i2c, pcf857x_id); > > > > > > > > +#ifdef CONFIG_OF > > > > +static const struct of_device_id pcf857x_of_table[] = { > > > > + { .compatible = "nxp,pcf8574", .data = (void *)8 }, > > > > + { .compatible = "nxp,pcf8574a", .data = (void *)8 }, > > > > + { .compatible = "nxp,pca8574", .data = (void *)8 }, > > > > + { .compatible = "nxp,pca9670", .data = (void *)8 }, > > > > + { .compatible = "nxp,pca9672", .data = (void *)8 }, > > > > + { .compatible = "nxp,pca9674", .data = (void *)8 }, > > > > + { .compatible = "nxp,pcf8575", .data = (void *)16 }, > > > > + { .compatible = "nxp,pca8575", .data = (void *)16 }, > > > > + { .compatible = "nxp,pca9671", .data = (void *)16 }, > > > > + { .compatible = "nxp,pca9673", .data = (void *)16 }, > > > > + { .compatible = "nxp,pca9675", .data = (void *)16 }, > > > > + { .compatible = "maxim,max7328", .data = (void *)8 }, > > > > + { .compatible = "maxim,max7329", .data = (void *)8 }, > > > > + { .compatible = "ti,tca9554", .data = (void *)8 }, > > > > + { } > > > > +}; > > > > +MODULE_DEVICE_TABLE(of, pcf857x_of_table); > > > > +#endif > > > > + > > > > > > > > /* > > > > > > > > * The pcf857x, pca857x, and pca967x chips only expose one read and > > > > one > > > > * write register. Writing a "one" bit (to match the reset state) > > > > lets > > > > > > > > @@ -257,14 +280,29 @@ fail: > > > > static int pcf857x_probe(struct i2c_client *client, > > > > > > > > const struct i2c_device_id *id) > > > > > > > > { > > > > > > > > - struct pcf857x_platform_data *pdata; > > > > + struct pcf857x_platform_data *pdata = client- > >dev.platform_data; > > > > + struct device_node *np = client->dev.of_node; > > > > > > > > struct pcf857x *gpio; > > > > > > > > + unsigned int n_latch = 0; > > > > + unsigned int ngpio; > > > > > > > > int status; > > > > > > > > - pdata = client->dev.platform_data; > > > > - if (!pdata) { > > > > +#ifdef CONFIG_OF > > > > + if (np) { > > > > > > Wouldn't if (IS_ENABLED(CONFIG_OF) && np) be sufficient here, without > > > the #ifdef? You would have to move the match table out of the #ifdef > > > in this case, though... > > > > That's the exact reason why I've used #ifdef CONFIG_OF here, I didn't > > want to add the overhead of the pcf857x_of_table when CONFIG_OF isn't > > defined. > > I'm not sure if I remember correctly, but I think there was something said > in one of discussions some time ago, that we should be moving away from > ifdef'ing such things, in favour of just having them compiled > unconditionally. I was also under this impression, but I have no strong feelings either way. Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/