Messages in this thread | | | Date | Wed, 16 Jul 2014 06:52:55 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH v4] hwmon: pwm-fan: Add pwm-fan driver |
| |
Hi Kamil,
comments inline.
Thanks, Guenter
On 07/16/2014 03:03 AM, Kamil Debski wrote: > The pwm-fan driver enables control of fans connected to PWM lines. > This driver uses the PWM framework, so it is compatible with all > PWM devices that provide drivers through the PWM framework. > > Signed-off-by: Kamil Debski <k.debski@samsung.com> > --- > Changes since v3: > - fix missing "\n" in error messages > - remove of_match_ptr which was not necessary > - change error returned in case of failed allocation to -ENOMEM > Changes since v2: > - add CONFIG_PM_SLEEP around pwm_fan_suspend and pwm_fan_resume > Changes since v1: > - added documentation to Documentation/hwmon > - fix checkpatch errors > - added extra description to Kconfig > - removed whitespace errors > - include files rearranged to be in alphabetical order > - remove unused sysfs entry pwm1_enable > - changed the behavior of the set_pwm function > - when 0 PWM value is set pwm_disable is run > - pwm_config return value is checked for errors > - use of ATTRIBUTE_GROUPS was added > - removed "Not enouch memory" error message > - fixed probe return value in case of devm_of_pwm_get error > - changed hwmon_device_register_with_groups to > devm_hwmon_device_register_with_groups > - changes suspend/resume to use pwm_disable/enable > - removed unnecessary CONFIG_PM_SLEEP ifdefs > --- > .../devicetree/bindings/hwmon/pwm-fan.txt | 12 ++ > Documentation/hwmon/pwm-fan | 17 ++ > drivers/hwmon/Kconfig | 11 ++ > drivers/hwmon/Makefile | 1 + > drivers/hwmon/pwm-fan.c | 202 ++++++++++++++++++++ > 5 files changed, 243 insertions(+) > create mode 100644 Documentation/devicetree/bindings/hwmon/pwm-fan.txt > create mode 100644 Documentation/hwmon/pwm-fan > create mode 100644 drivers/hwmon/pwm-fan.c > > diff --git a/Documentation/devicetree/bindings/hwmon/pwm-fan.txt b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt > new file mode 100644 > index 0000000..610757c > --- /dev/null > +++ b/Documentation/devicetree/bindings/hwmon/pwm-fan.txt > @@ -0,0 +1,12 @@ > +Bindings for a fan connected to the PWM lines > + > +Required properties: > +- compatible : "pwm-fan" > +- pwms : the PWM that is used to control the PWM fan > + > +Example: > + pwm-fan { > + compatible = "pwm-fan"; > + status = "okay"; > + pwms = <&pwm 0 10000 0>; > + }; > diff --git a/Documentation/hwmon/pwm-fan b/Documentation/hwmon/pwm-fan > new file mode 100644 > index 0000000..18529d2 > --- /dev/null > +++ b/Documentation/hwmon/pwm-fan > @@ -0,0 +1,17 @@ > +Kernel driver pwm-fan > +===================== > + > +This driver enables the use of a PWM module to drive a fan. It uses the > +generic PWM interface thus it is hardware independent. It can be used on > +many SoCs, as long as the SoC supplies a PWM line driver that exposes > +the generic PWM API. > + > +Author: Kamil Debski <k.debski@samsung.com> > + > +Description > +----------- > + > +The driver implements a simple interface for driving a fan connected to > +a PWM output. It uses the generic PWM interface, thus it can be used with > +a range of SoCs. The driver exposes the fan to the user space through > +the hwmon's sysfs interface. > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig > index 02d3d85..4ac13ab 100644 > --- a/drivers/hwmon/Kconfig > +++ b/drivers/hwmon/Kconfig > @@ -1105,6 +1105,17 @@ config SENSORS_PCF8591 > > source drivers/hwmon/pmbus/Kconfig > > +config SENSORS_PWM_FAN > + tristate "PWM fan" > + depends on PWM > + help > + If you say yes here you get support for fans connected to PWM lines. > + The driver uses the generic PWM interface, thus it will work on a > + variety of SoCs. > + > + This driver can also be built as a module. If so, the module > + will be called pwm-fan. > + > config SENSORS_SHT15 > tristate "Sensiron humidity and temperature sensors. SHT15 and compat." > depends on GPIOLIB > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile > index 3dc0f02..3967ecf 100644 > --- a/drivers/hwmon/Makefile > +++ b/drivers/hwmon/Makefile > @@ -120,6 +120,7 @@ obj-$(CONFIG_SENSORS_NTC_THERMISTOR) += ntc_thermistor.o > obj-$(CONFIG_SENSORS_PC87360) += pc87360.o > obj-$(CONFIG_SENSORS_PC87427) += pc87427.o > obj-$(CONFIG_SENSORS_PCF8591) += pcf8591.o > +obj-$(CONFIG_SENSORS_PWM_FAN) += pwm-fan.o > obj-$(CONFIG_SENSORS_S3C) += s3c-hwmon.o > obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o > obj-$(CONFIG_SENSORS_SCH5627) += sch5627.o > diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c > new file mode 100644 > index 0000000..cacb20a > --- /dev/null > +++ b/drivers/hwmon/pwm-fan.c > @@ -0,0 +1,202 @@ > +/* > + * pwm-fan.c - Hwmon driver for fans connected to PWM lines. > + * > + * Copyright (c) 2014 Samsung Electronics Co., Ltd. > + * > + * Author: Kamil Debski <k.debski@samsung.com> > + * > + * 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. > + */ > + > +#include <linux/hwmon.h> > +#include <linux/hwmon-sysfs.h> > +#include <linux/module.h> > +#include <linux/mutex.h> > +#include <linux/of.h> > +#include <linux/platform_device.h> > +#include <linux/pwm.h> > +#include <linux/sysfs.h> > + > +#define MAX_PWM 255 > + > +struct pwm_fan_ctx { > + struct device *hwmon; > + struct mutex lock; > + struct platform_device *pdev;
Neither hwmon nor pdev are used anywhere and are thus unnecessary.
> + struct pwm_device *pwm; > + unsigned int duty_cycle;
duty_cycle is only used in the probe function, and is thus unnecessary as well.
> + unsigned char pwm_value; > +}; > + > +static ssize_t set_pwm(struct device *dev, struct device_attribute *attr, > + const char *buf, size_t count) > +{ > + struct pwm_fan_ctx *ctx = dev_get_drvdata(dev); > + unsigned long pwm, duty; > + int ret; > + > + if (kstrtoul(buf, 10, &pwm) || pwm > MAX_PWM) > + return -EINVAL; > + > + mutex_lock(&ctx->lock); > + > + if (ctx->pwm_value == pwm) > + goto exit_set_pwm; > + > + if (pwm == 0) { > + pwm_disable(ctx->pwm); > + ctx->pwm_value = pwm; > + goto exit_set_pwm;
You can add another label below to save the double assignment.
> + } > + > + duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM); > + ret = pwm_config(ctx->pwm, duty, ctx->pwm->period); > + if (ret) { > + count = ret; /* Set the return value */
Subtle problem: count is of type size_t which is unsigned. Sure it may well be that the negative value is converted to unsigned and then converted back to signed on return, but it is not a good idea to depend on it. I would suggest to return ret and assign ret = count; in the success case further below. You'll need an extra label for the success cases above.
> + goto exit_set_pwm; > + } > + > + if (ctx->pwm_value == 0) > + ret = pwm_enable(ctx->pwm); > + if (ret) { > + count = ret; /* Set the return value */ > + goto exit_set_pwm; > + }
This check for ret should really be within the if() statement.
> + > + ctx->duty_cycle = duty; > + ctx->pwm_value = pwm; > + > +exit_set_pwm: > + mutex_unlock(&ctx->lock); > + return count; > +} > + > +static ssize_t show_pwm(struct device *dev, > + struct device_attribute *attr, char *buf) > +{ > + struct pwm_fan_ctx *ctx = dev_get_drvdata(dev); > + > + return sprintf(buf, "%u\n", ctx->pwm_value); > +} > + > + > +static SENSOR_DEVICE_ATTR(pwm1, S_IRUGO | S_IWUSR, > + show_pwm, set_pwm, 0); > + Continuation line is not needed here.
> +static struct attribute *pwm_fan_attrs[] = { > + &sensor_dev_attr_pwm1.dev_attr.attr, > + NULL, > +}; > + > +ATTRIBUTE_GROUPS(pwm_fan); > + > +static int pwm_fan_probe(struct platform_device *pdev) > +{ > + struct pwm_fan_ctx *ctx; > + int ret; > + > + ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL); > + if (!ctx) > + return -ENOMEM; > + > + ctx->pdev = pdev; > + mutex_init(&ctx->lock); > + > + ctx->pwm = devm_of_pwm_get(&pdev->dev, pdev->dev.of_node, 0); > + if (IS_ERR(ctx->pwm)) { > + dev_err(&pdev->dev, "Could not get PWM\n"); > + return PTR_ERR(ctx->pwm); > + } > + > + dev_set_drvdata(&pdev->dev, ctx); > + platform_set_drvdata(pdev, ctx); > + > + /* Set duty cycle to maximum allowed */ > + ctx->duty_cycle = ctx->pwm->period - 1; > + ctx->pwm_value = MAX_PWM; > + > + ret = pwm_config(ctx->pwm, ctx->duty_cycle, ctx->pwm->period); > + if (ret) { > + dev_err(&pdev->dev, "Failed to configure PWM\n"); > + return ret; > + } > + > + /* Enbale PWM output */ > + ret = pwm_enable(ctx->pwm); > + if (ret) { > + dev_err(&pdev->dev, "Failed to enable PWM\n"); > + return ret; > + } > + > + ctx->hwmon = devm_hwmon_device_register_with_groups(&pdev->dev, > + "pwmfan", ctx, > + pwm_fan_groups); > + > + if (IS_ERR(ctx->hwmon)) { > + dev_err(&pdev->dev, "Failed to register hwmon device\n"); > + pwm_disable(ctx->pwm); > + return PTR_ERR(ctx->hwmon); > + } > + return 0; > +} > + > +static int pwm_fan_remove(struct platform_device *pdev) > +{ > + struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev); > + > + if (ctx->pwm_value) > + pwm_disable(ctx->pwm); > + return 0; > +} > + > +#ifdef CONFIG_PM_SLEEP > +static int pwm_fan_suspend(struct device *dev) > +{ > + struct pwm_fan_ctx *ctx = dev_get_drvdata(dev); > + > + if (ctx->pwm_value) > + pwm_disable(ctx->pwm); > + return 0; > +} > + > +static int pwm_fan_resume(struct device *dev) > +{ > + struct pwm_fan_ctx *ctx = dev_get_drvdata(dev); > + > + if (ctx->pwm_value) > + return pwm_enable(ctx->pwm); > + return 0; > +} > +#endif > + > +static SIMPLE_DEV_PM_OPS(pwm_fan_pm, pwm_fan_suspend, pwm_fan_resume); > + > +static struct of_device_id of_pwm_fan_match[] = { > + { .compatible = "pwm-fan", }, > + {}, > +}; > + > +static struct platform_driver pwm_fan_driver = { > + .probe = pwm_fan_probe, > + .remove = pwm_fan_remove, > + .driver = { > + .name = "pwm-fan", > + .pm = &pwm_fan_pm, > + .of_match_table = of_pwm_fan_match, > + }, > +}; > + > +module_platform_driver(pwm_fan_driver); > + > +MODULE_AUTHOR("Kamil Debski <k.debski@samsung.com>"); > +MODULE_ALIAS("platform:pwm-fan"); > +MODULE_DESCRIPTION("PWM FAN driver"); > +MODULE_LICENSE("GPL"); >
| |