Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752535AbdHGJD6 (ORCPT ); Mon, 7 Aug 2017 05:03:58 -0400 Received: from mail-io0-f172.google.com ([209.85.223.172]:35112 "EHLO mail-io0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752454AbdHGJDz (ORCPT ); Mon, 7 Aug 2017 05:03:55 -0400 MIME-Version: 1.0 In-Reply-To: <20170731222452.22887-1-danilokrummrich@dk-develop.de> References: <20170731222452.22887-1-danilokrummrich@dk-develop.de> From: Linus Walleij Date: Mon, 7 Aug 2017 11:03:53 +0200 Message-ID: Subject: Re: [PATCH] serio: PS2 gpio bit banging driver for the serio bus To: Danilo Krummrich Cc: "linux-kernel@vger.kernel.org" , Linux Input , Dmitry Torokhov , "devicetree@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5166 Lines: 164 On Tue, Aug 1, 2017 at 12:24 AM, Danilo Krummrich wrote: > This driver provides PS2 serio bus support by implementing bit banging > with the GPIO API. The GPIO pins, data and clock, can be configured with > a node in the device tree or by static platform data. > > Writing to a device is supported as well, though it is not recommended as > the timings to be halt given by libps2 are very tough and difficult to > reach with bit banging. Therefore it can be configured (also in DT and > pdata) whether the serio write function should be available for clients. > > This driver is for development purposes and not for productive use. > However, this driver can be useful e.g. when no USB port is available or > using old peripherals is desired as PS2 controllers getting rare. > > This driver was tested on a RPI1 and on Hikey960 and it worked well > together with the atkbd driver. > > Signed-off-by: Danilo Krummrich > +++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt When you add DT bindings you have to CC devicetree@vger.kernel.org > @@ -0,0 +1,20 @@ > +Device-Tree bindings for ps2 gpio driver > + > +Required properties: > + - compatible = "ps2-gpio"; > + - gpios: data and clock gpio > + > +Optional properties: > + - ps2-gpio,write-enable: Indicates whether write function is provided > + to serio device. Most probably providing the write fn will not work, > + because of the tough timing libps2 requires. > + > +Example nodes: > + > +ps2@0 { > + compatible = "ps2-gpio"; > + gpios = <&gpio 24 0 /* data */ > + &gpio 23 0 /* clock */ > + >; > + i2c-gpio,write-enable = <0>; > +}; These look fine to me though. > diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt Thanks for patching this! > +config SERIO_GPIO_PS2 > + tristate "GPIO PS/2 bit banging driver" > + help > + Say Y here if you want PS/2 bit banging support via GPIO. > + > + To compile this driver as a module, choose M here: the > + module will be called gpio-ps2. > + > + If you are unsure, say N. As mentioned depends on GPIOLIB depends on OF > +#include Use only: #include > +#include Should not be needed. > +struct ps2_gpio_data { > + struct device *dev; > + struct serio *serio; > + unsigned char mode; > + unsigned int gpio_clk; > + unsigned int gpio_data; > + unsigned int write_enable; Do not use the global GPIO number space, use GPIO descriptors. Example: drivers/input/keyboard/gpio_keys.c > +static int ps2_gpio_write(struct serio *serio, unsigned char val) > +{ > + struct ps2_gpio_data *drvdata = serio->port_data; > + > + drvdata->mode = PS2_MODE_TX; > + drvdata->tx_byte = val; > + /* Make sure ISR running on other CPU notice changes. */ > + barrier(); This seems overengineered, is this really needed? If we have races like this, the error is likely elsewhere, and should be fixed in the GPIO driver MMIO access or so. > + disable_irq_nosync(drvdata->irq); > + gpio_direction_output(drvdata->gpio_clk, 0); No use GPIO descriptors please. > + // dev_info(drvdata->dev, "recv bit %u: %u\n", cnt, data); Delete comments or convert to dev_dbg() > +static int of_ps2_gpio_get_props(struct device *dev, > + struct ps2_gpio_data *drvdata) > +{ > + if (of_gpio_count(dev->of_node) < 2) > + return -ENODEV; > + > + drvdata->gpio_data = of_get_gpio(dev->of_node, 0); > + drvdata->gpio_clk = of_get_gpio(dev->of_node, 1); > + > + if (drvdata->gpio_data == -EPROBE_DEFER || > + drvdata->gpio_clk == -EPROBE_DEFER) > + return -EPROBE_DEFER; > + > + if (!gpio_is_valid(drvdata->gpio_data) || > + !gpio_is_valid(drvdata->gpio_clk)) { > + dev_err(dev, "invalid GPIOs, data=%d, clk=%d\n", > + drvdata->gpio_data, drvdata->gpio_clk); > + return -ENODEV; > + } With GPIO descriptors you should just gpiod_get(dev, "foo", FLAG); No need to poke around in the device tree like this. Error checks and deferrals apply as usual though. > + error = devm_gpio_request(dev, drvdata->gpio_clk, "ps2 clk"); > + if (error) { > + dev_err(dev, "failed to request gpio %u: %d", > + drvdata->gpio_clk, error); > + goto err_free_serio; > + } > + > + error = devm_gpio_request(dev, drvdata->gpio_data, "ps2 data"); > + if (error) { > + dev_err(dev, "failed to request gpio %u: %d", > + drvdata->gpio_data, error); > + goto err_free_serio; > + } So devm_gpiod_get(...) > + gpio_direction_input(drvdata->gpio_clk); > + gpio_direction_input(drvdata->gpio_data); And incidentallt then you can just specify GPIOD_IN as flag and it will be set up for you. Yours, Linus Walleij