From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757825AbXLFDEV (ORCPT ); Wed, 5 Dec 2007 22:04:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756962AbXLFDDU (ORCPT ); Wed, 5 Dec 2007 22:03:20 -0500 Received: from smtp117.sbc.mail.sp1.yahoo.com ([69.147.64.90]:37957 "HELO smtp117.sbc.mail.sp1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1757828AbXLFDDR (ORCPT ); Wed, 5 Dec 2007 22:03:17 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=pacbell.net; h=Received:X-YMail-OSG:From:To:Subject:Date:User-Agent:Cc:References:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Content-Disposition:Message-Id; b=I8+fnnYfnheETr3e/QwG8LApfJBNpovDplSwmv1rnjnfFY9bt12JC22AkIwkYH4U02s0i+n9ELTf0hAIlsWchJ3Nlc1eNahxpg5GODdS77JJFZvRzB45Zaw3ShUiP/vKXEcnEr+egHvlHjkP2h7/zjWlAkx1C1d/rO9EvtZiTug= ; X-YMail-OSG: uKQhDG8VM1mVRgbmhmGiBMi9v5GuhRnBEGIqVgSoK1EGl2t67aNvLfhO9S7AFdy25JCGP7HSSQ-- From: David Brownell To: Jean Delvare Subject: Re: [patch/rfc 2/4] pcf857x I2C GPIO expander driver Date: Wed, 5 Dec 2007 19:03:12 -0800 User-Agent: KMail/1.9.6 Cc: Linux Kernel list , Felipe Balbi , Bill Gatliff , Haavard Skinnemoen , Andrew Victor , Tony Lindgren , "eric miao" , Kevin Hilman , Paul Mundt , Ben Dooks References: <200710291809.29936.david-b@pacbell.net> <20071130133256.72385ea8@hyperion.delvare> <200711301040.54777.david-b@pacbell.net> In-Reply-To: <200711301040.54777.david-b@pacbell.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Content-Disposition: inline Message-Id: <200712051903.13932.david-b@pacbell.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 30 November 2007, David Brownell wrote: > Thanks for the review.  I'll snip out typos and similar trivial > comments (and fix them!), using responses here for more the > substantive feedback. Here's the current version of this patch ... updated to put the driver into drivers/gpio (separate patch setting that up) and the header into Note that after looking at the GPIO expanders listed at the NXP website, I updated this to accept a few more of these chips. Other than reset pins and addressing options, the key difference between these seems to be the top I2C clock speed supported: pcf857x ... 100 KHz pca857x ... 400 KHz pca967x ... 1000 KHz Otherwise they're equivalent at the level of just swapping parts. - Dave ============= SNIP! This is a new-style I2C driver for most common 8 and 16 bit I2C based "quasi-bidirectional" GPIO expanders: pcf8574 or pcf8575, and several compatible models (mostly faster, supporting I2C at up to 1 MHz). Since it's a new-style driver, these devices must be configured as part of board-specific init. That eliminates the need for error-prone manual configuration of module parameters, and makes compatibility with legacy drivers (pcf8574.c, pc8575.c)for these chips easier. The driver exposes the GPIO signals using the platform-neutral GPIO programming interface, so they are easily accessed by other kernel code. The lack of such a flexible kernel API is what has ensured the proliferation of board-specific drivers for these chips... stuff that rarely makes it upstream since it's so ugly. This driver will let them use standard calls. Signed-off-by: David Brownell --- drivers/gpio/Kconfig | 23 +++ drivers/gpio/Makefile | 2 drivers/gpio/pcf857x.c | 331 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c/pcf857x.h | 45 +++++ 4 files changed, 401 insertions(+) --- a/drivers/gpio/Kconfig 2007-12-05 15:13:27.000000000 -0800 +++ b/drivers/gpio/Kconfig 2007-12-05 15:14:12.000000000 -0800 @@ -5,4 +5,27 @@ menu "GPIO Support" depends on GPIO_LIB +config GPIO_PCF857X + tristate "PCF857x, PCA857x, and PCA967x I2C GPIO expanders" + depends on I2C + help + Say yes here to provide access to most "quasi-bidirectional" I2C + GPIO expanders used for additional digital outputs or inputs. + Most of these parts are from NXP, though TI is a second source for + some of them. Compatible models include: + + 8 bits: pcf8574, pcf8574a, pca8574, pca8574a, + pca9670, pca9672, pca9674, pca9674a + + 16 bits: pcf8575, pcf8575c, pca8575, + pca9671, pca9673, pca9675 + + Your board setup code will need to declare the expanders in + use, and assign numbers to the GPIOs they expose. Those GPIOs + can then be used from drivers and other kernel code, just like + other GPIOs, but only accessible from task contexts. + + This driver provides an in-kernel interface to those GPIOs using + platform-neutral GPIO calls. + endmenu --- a/drivers/gpio/Makefile 2007-12-05 15:14:03.000000000 -0800 +++ b/drivers/gpio/Makefile 2007-12-05 15:14:12.000000000 -0800 @@ -1 +1,3 @@ # gpio support: dedicated expander chips, etc + +obj-$(CONFIG_GPIO_PCF857X) += pcf857x.o --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ b/drivers/gpio/pcf857x.c 2007-12-05 15:15:18.000000000 -0800 @@ -0,0 +1,331 @@ +/* + * pcf857x - driver for pcf857x, pca857x, and pca967x I2C GPIO expanders + * + * Copyright (C) 2007 David Brownell + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include +#include +#include +#include + +#include + + +/* + * The pcf857x, pca857x, and pca967x chips only expose one read and one + * write register. Writing a "one" bit (to match the reset state) lets + * that pin be used as an input; it's not an open-drain model, but acts + * a bit like one. This is described as "quasi-bidirectional"; read the + * chip documentation for details. + * + * Some other I2C GPIO expander chips (like the pca953{4,5,6,7,9}, pca9555, + * pca9698, mcp23008, and mc23017) have more complex register models with + * more conventional input circuitry, often using 0x20..0x27 addresses. + */ +struct pcf857x { + struct gpio_chip chip; + struct i2c_client *client; + unsigned out; /* software latch */ +}; + +/*-------------------------------------------------------------------------*/ + +/* Talk to 8-bit I/O expander */ + +static int pcf857x_input8(struct gpio_chip *chip, unsigned offset) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + + gpio->out |= (1 << offset); + return i2c_smbus_write_byte(gpio->client, gpio->out); +} + +static int pcf857x_get8(struct gpio_chip *chip, unsigned offset) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + s32 value; + + value = i2c_smbus_read_byte(gpio->client); + return (value < 0) ? 0 : (value & (1 << offset)); +} + +static int pcf857x_output8(struct gpio_chip *chip, unsigned offset, int value) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + unsigned bit = 1 << offset; + + if (value) + gpio->out |= bit; + else + gpio->out &= ~bit; + return i2c_smbus_write_byte(gpio->client, gpio->out); +} + +static void pcf857x_set8(struct gpio_chip *chip, unsigned offset, int value) +{ + pcf857x_output8(chip, offset, value); +} + +/*-------------------------------------------------------------------------*/ + +/* Talk to 16-bit I/O expander */ + +static int i2c_write_le16(struct i2c_client *client, u16 word) +{ + u8 buf[2] = { word & 0xff, word >> 8, }; + int status; + + status = i2c_master_send(client, buf, 2); + return (status < 0) ? status : 0; +} + +static int i2c_read_le16(struct i2c_client *client) +{ + u8 buf[2]; + int status; + + status = i2c_master_recv(client, buf, 2); + if (status < 0) + return status; + return (buf[1] << 8) | buf[0]; +} + +static int pcf857x_input16(struct gpio_chip *chip, unsigned offset) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + + gpio->out |= (1 << offset); + return i2c_write_le16(gpio->client, gpio->out); +} + +static int pcf857x_get16(struct gpio_chip *chip, unsigned offset) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + int value; + + value = i2c_read_le16(gpio->client); + return (value < 0) ? 0 : (value & (1 << offset)); +} + +static int pcf857x_output16(struct gpio_chip *chip, unsigned offset, int value) +{ + struct pcf857x *gpio = container_of(chip, struct pcf857x, chip); + unsigned bit = 1 << offset; + + if (value) + gpio->out |= bit; + else + gpio->out &= ~bit; + return i2c_write_le16(gpio->client, gpio->out); +} + +static void pcf857x_set16(struct gpio_chip *chip, unsigned offset, int value) +{ + pcf857x_output16(chip, offset, value); +} + +/*-------------------------------------------------------------------------*/ + +static int pcf857x_probe(struct i2c_client *client) +{ + struct pcf857x_platform_data *pdata; + struct pcf857x *gpio; + int status; + + pdata = client->dev.platform_data; + if (!pdata) + return -ENODEV; + + /* Allocate, initialize, and register this gpio_chip. */ + gpio = kzalloc(sizeof *gpio, GFP_KERNEL); + if (!gpio) + return -ENOMEM; + + gpio->chip.base = pdata->gpio_base; + gpio->chip.can_sleep = 1; + + /* NOTE: the OnSemi jlc1562b is also largely compatible with + * these parts, notably for output. It has a low-resolution + * DAC instead of pin change IRQs; and its inputs can be the + * result of comparators. + */ + + /* 8574 addresses are 0x20..0x27; 8574a uses 0x38..0x3f; + * 9670, 9672, 9764, and 9764a use quite a variety. + * + * NOTE: we dont distinguish here between *4 and *4a parts. + */ + if (strcmp(client->name, "pcf8574") == 0 + || strcmp(client->name, "pca8574") == 0 + || strcmp(client->name, "pca9670") == 0 + || strcmp(client->name, "pca9672") == 0 + || strcmp(client->name, "pca9674") == 0 + ) { + gpio->chip.ngpio = 8; + gpio->chip.direction_input = pcf857x_input8; + gpio->chip.get = pcf857x_get8; + gpio->chip.direction_output = pcf857x_output8; + gpio->chip.set = pcf857x_set8; + + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_BYTE)) + status = -EIO; + + /* fail if there's no chip present */ + else + status = i2c_smbus_read_byte(client); + + /* '75/'75c addresses are 0x20..0x27, just like the '74; + * the '75c doesn't have a current source pulling high. + * 9671, 9673, and 9765 use quite a variety of addresses. + * + * NOTE: we dont distinguish here between 8575/8575a parts. + */ + } else if (strcmp(client->name, "pcf8575") == 0 + || strcmp(client->name, "pca8575") == 0 + || strcmp(client->name, "pca9671") == 0 + || strcmp(client->name, "pca9673") == 0 + || strcmp(client->name, "pca9675") == 0 + ) { + gpio->chip.ngpio = 16; + gpio->chip.direction_input = pcf857x_input16; + gpio->chip.get = pcf857x_get16; + gpio->chip.direction_output = pcf857x_output16; + gpio->chip.set = pcf857x_set16; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) + status = -EIO; + + /* fail if there's no chip present */ + else + status = i2c_read_le16(client); + + } else + status = -ENODEV; + + if (status < 0) + goto fail; + + gpio->chip.label = client->name; + + gpio->client = client; + i2c_set_clientdata(client, gpio); + + /* NOTE: these chips have strange "quasi-bidirectional" I/O pins. + * We can't actually know whether a pin is configured (a) as output + * and driving the signal low, or (b) as input and reporting a low + * value ... without knowing the last value written since the chip + * came out of reset (if any). We can't read the latched output. + * + * In short, the only reliable solution for setting up pin direction + * is to do it explicitly. The setup() method can do that. + * + * We use pdata->n_latch to avoid trouble. In the typical case it's + * left initialized to zero; our software copy of the "latch" then + * matches the chip's all-ones reset state. But some systems will + * need to drive some pins low, while avoiding transient glitches. + * Handle those cases by assigning n_latch to a nonzero value. + */ + gpio->out = ~pdata->n_latch; + + status = gpiochip_add(&gpio->chip); + if (status < 0) + goto fail; + + /* NOTE: these chips can issue "some pin-changed" IRQs, which we + * don't yet even try to use. Among other issues, the relevant + * genirq state isn't available to modular drivers; and most irq + * methods can't be called from sleeping contexts. + */ + + dev_info(&client->dev, "gpios %d..%d on a %s%s\n", + gpio->chip.base, + gpio->chip.base + gpio->chip.ngpio - 1, + client->name, + client->irq ? " (irq ignored)" : ""); + + /* Let platform code set up the GPIOs and their users. + * Now is the first time anyone can use them. + */ + if (pdata->setup) { + status = pdata->setup(client, + gpio->chip.base, gpio->chip.ngpio, + pdata->context); + if (status < 0) + dev_err(&client->dev, "%s --> %d\n", + "setup", status); + } + + return 0; + +fail: + dev_dbg(&client->dev, "probe error %d for '%s'\n", + status, client->name); + kfree(gpio); + return status; +} + +static int pcf857x_remove(struct i2c_client *client) +{ + struct pcf857x_platform_data *pdata = client->dev.platform_data; + struct pcf857x *gpio = i2c_get_clientdata(client); + int status = 0; + + if (pdata->teardown) { + status = pdata->teardown(client, + gpio->chip.base, gpio->chip.ngpio, + pdata->context); + if (status < 0) { + dev_err(&client->dev, "%s --> %d\n", + "teardown", status); + return status; + } + } + + status = gpiochip_remove(&gpio->chip); + if (status == 0) + kfree(gpio); + else + dev_err(&client->dev, "%s --> %d\n", "remove", status); + return status; +} + +static struct i2c_driver pcf857x_driver = { + .driver = { + .name = "pcf857x", + .owner = THIS_MODULE, + }, + .probe = pcf857x_probe, + .remove = pcf857x_remove, +}; + +static int __init pcf857x_init(void) +{ + return i2c_add_driver(&pcf857x_driver); +} +/* we want GPIOs to be ready at device_initcall() time */ +subsys_initcall(pcf857x_init); + +static void __exit pcf857x_exit(void) +{ + i2c_del_driver(&pcf857x_driver); +} +module_exit(pcf857x_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("David Brownell"); --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ b/include/linux/i2c/pcf857x.h 2007-12-05 15:14:12.000000000 -0800 @@ -0,0 +1,45 @@ +#ifndef __LINUX_PCF857X_H +#define __LINUX_PCF857X_H + +/** + * struct pcf857x_platform_data - data to set up pcf857x driver + * @gpio_base: number of the chip's first GPIO + * @n_latch: optional bit-inverse of initial register value; if + * you leave this initialized to zero the driver will act + * like the chip was just reset + * @setup: optional callback issued once the GPIOs are valid + * @teardown: optional callback issued before the GPIOs are invalidated + * @context: optional parameter passed to setup() and teardown() + * + * In addition to the I2C_BOARD_INFO() state appropriate to each chip, + * the i2c_board_info used with the pcf875x driver must provide the + * chip "type" ("pcf8574", "pcf8574a", "pcf8575", "pcf8575c") and its + * platform_data (pointer to one of these structures) with at least + * the gpio_base value initialized. + * + * The @setup callback may be used with the kind of board-specific glue + * which hands the (now-valid) GPIOs to other drivers, or which puts + * devices in their initial states using these GPIOs. + * + * These GPIO chips are only "quasi-bidirectional"; read the chip specs + * to understand the behavior. They don't have separate registers to + * record which pins are used for input or output, record which output + * values are driven, or provide access to input values. That must be + * inferred by reading the chip's value and knowing the last value written + * to it. If you leave n_latch initialized to zero, that last written + * value is presumed to be all ones (as if the chip were just reset). + */ +struct pcf857x_platform_data { + unsigned gpio_base; + unsigned n_latch; + + int (*setup)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); + int (*teardown)(struct i2c_client *client, + int gpio, unsigned ngpio, + void *context); + void *context; +}; + +#endif /* __LINUX_PCF857X_H */