pwm: Add sysfs interface
Add a simple sysfs interface to the generic PWM framework.
/sys/class/pwm/
`-- pwmchipN/ for each PWM chip
|-- export (w/o) ask the kernel to export a PWM channel
|-- npwm (r/o) number of PWM channels in this PWM chip
|-- pwmX/ for each exported PWM channel
| |-- duty_cycle (r/w) duty cycle (in nanoseconds)
| |-- enable (r/w) enable/disable PWM
| |-- period (r/w) period (in nanoseconds)
| `-- polarity (r/w) polarity of PWM (normal/inversed)
`-- unexport (w/o) return a PWM channel to the kernel
Based on work by Lars Poeschel.
Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Ryan Mallon <rmallon@gmail.com>
Cc: Rob Landley <rob@landley.net>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
H Hartley Sweeten
Thierry Reding
parent
3dd0a90947
commit
76abbdde2d
|
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@ -0,0 +1,79 @@
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What: /sys/class/pwm/
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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The pwm/ class sub-directory belongs to the Generic PWM
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Framework and provides a sysfs interface for using PWM
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channels.
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What: /sys/class/pwm/pwmchipN/
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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A /sys/class/pwm/pwmchipN directory is created for each
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probed PWM controller/chip where N is the base of the
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PWM chip.
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What: /sys/class/pwm/pwmchipN/npwm
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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The number of PWM channels supported by the PWM chip.
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What: /sys/class/pwm/pwmchipN/export
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Exports a PWM channel from the PWM chip for sysfs control.
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Value is between 0 and /sys/class/pwm/pwmchipN/npwm - 1.
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What: /sys/class/pwm/pwmchipN/unexport
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Unexports a PWM channel.
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What: /sys/class/pwm/pwmchipN/pwmX
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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A /sys/class/pwm/pwmchipN/pwmX directory is created for
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each exported PWM channel where X is the exported PWM
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channel number.
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What: /sys/class/pwm/pwmchipN/pwmX/period
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Sets the PWM signal period in nanoseconds.
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What: /sys/class/pwm/pwmchipN/pwmX/duty_cycle
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Sets the PWM signal duty cycle in nanoseconds.
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What: /sys/class/pwm/pwmchipN/pwmX/polarity
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Sets the output polarity of the PWM signal to "normal" or
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"inversed".
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What: /sys/class/pwm/pwmchipN/pwmX/enable
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Date: May 2013
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KernelVersion: 3.11
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Contact: H Hartley Sweeten <hsweeten@visionengravers.com>
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Description:
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Enable/disable the PWM signal.
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0 is disabled
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1 is enabled
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@ -45,6 +45,43 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
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To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
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Using PWMs with the sysfs interface
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-----------------------------------
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If CONFIG_SYSFS is enabled in your kernel configuration a simple sysfs
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interface is provided to use the PWMs from userspace. It is exposed at
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/sys/class/pwm/. Each probed PWM controller/chip will be exported as
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pwmchipN, where N is the base of the PWM chip. Inside the directory you
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will find:
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npwm - The number of PWM channels this chip supports (read-only).
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export - Exports a PWM channel for use with sysfs (write-only).
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unexport - Unexports a PWM channel from sysfs (write-only).
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The PWM channels are numbered using a per-chip index from 0 to npwm-1.
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When a PWM channel is exported a pwmX directory will be created in the
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pwmchipN directory it is associated with, where X is the number of the
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channel that was exported. The following properties will then be available:
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period - The total period of the PWM signal (read/write).
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Value is in nanoseconds and is the sum of the active and inactive
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time of the PWM.
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duty_cycle - The active time of the PWM signal (read/write).
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Value is in nanoseconds and must be less than the period.
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polarity - Changes the polarity of the PWM signal (read/write).
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Writes to this property only work if the PWM chip supports changing
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the polarity. The polarity can only be changed if the PWM is not
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enabled. Value is the string "normal" or "inversed".
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enable - Enable/disable the PWM signal (read/write).
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0 - disabled
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1 - enabled
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Implementing a PWM driver
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-------------------------
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@ -28,6 +28,10 @@ menuconfig PWM
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if PWM
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config PWM_SYSFS
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bool
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default y if SYSFS
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config PWM_AB8500
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tristate "AB8500 PWM support"
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depends on AB8500_CORE && ARCH_U8500
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@ -1,4 +1,5 @@
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obj-$(CONFIG_PWM) += core.o
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obj-$(CONFIG_PWM_SYSFS) += sysfs.o
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obj-$(CONFIG_PWM_AB8500) += pwm-ab8500.o
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obj-$(CONFIG_PWM_ATMEL_TCB) += pwm-atmel-tcb.o
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obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
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@ -274,6 +274,8 @@ int pwmchip_add(struct pwm_chip *chip)
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if (IS_ENABLED(CONFIG_OF))
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of_pwmchip_add(chip);
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pwmchip_sysfs_export(chip);
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out:
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mutex_unlock(&pwm_lock);
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return ret;
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@ -310,6 +312,8 @@ int pwmchip_remove(struct pwm_chip *chip)
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free_pwms(chip);
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pwmchip_sysfs_unexport(chip);
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out:
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mutex_unlock(&pwm_lock);
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return ret;
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@ -402,10 +406,19 @@ EXPORT_SYMBOL_GPL(pwm_free);
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*/
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int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
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{
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int err;
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if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
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return -EINVAL;
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return pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
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err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
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if (err)
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return err;
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pwm->duty_cycle = duty_ns;
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pwm->period = period_ns;
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return 0;
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}
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EXPORT_SYMBOL_GPL(pwm_config);
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@ -418,6 +431,8 @@ EXPORT_SYMBOL_GPL(pwm_config);
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*/
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int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
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{
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int err;
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if (!pwm || !pwm->chip->ops)
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return -EINVAL;
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@ -427,7 +442,13 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
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if (test_bit(PWMF_ENABLED, &pwm->flags))
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return -EBUSY;
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return pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
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err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
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if (err)
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return err;
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pwm->polarity = polarity;
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return 0;
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}
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EXPORT_SYMBOL_GPL(pwm_set_polarity);
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@ -0,0 +1,352 @@
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/*
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* A simple sysfs interface for the generic PWM framework
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*
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* Copyright (C) 2013 H Hartley Sweeten <hsweeten@visionengravers.com>
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*
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* Based on previous work by Lars Poeschel <poeschel@lemonage.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/device.h>
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#include <linux/mutex.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/kdev_t.h>
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#include <linux/pwm.h>
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struct pwm_export {
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struct device child;
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struct pwm_device *pwm;
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};
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static struct pwm_export *child_to_pwm_export(struct device *child)
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{
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return container_of(child, struct pwm_export, child);
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}
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static struct pwm_device *child_to_pwm_device(struct device *child)
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{
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struct pwm_export *export = child_to_pwm_export(child);
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return export->pwm;
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}
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static ssize_t pwm_period_show(struct device *child,
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struct device_attribute *attr,
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char *buf)
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{
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const struct pwm_device *pwm = child_to_pwm_device(child);
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return sprintf(buf, "%u\n", pwm->period);
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}
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static ssize_t pwm_period_store(struct device *child,
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struct device_attribute *attr,
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const char *buf, size_t size)
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{
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struct pwm_device *pwm = child_to_pwm_device(child);
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unsigned int val;
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int ret;
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ret = kstrtouint(buf, 0, &val);
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if (ret)
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return ret;
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ret = pwm_config(pwm, pwm->duty_cycle, val);
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return ret ? : size;
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}
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static ssize_t pwm_duty_cycle_show(struct device *child,
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struct device_attribute *attr,
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char *buf)
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{
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const struct pwm_device *pwm = child_to_pwm_device(child);
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return sprintf(buf, "%u\n", pwm->duty_cycle);
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}
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static ssize_t pwm_duty_cycle_store(struct device *child,
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struct device_attribute *attr,
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const char *buf, size_t size)
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{
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struct pwm_device *pwm = child_to_pwm_device(child);
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unsigned int val;
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int ret;
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ret = kstrtouint(buf, 0, &val);
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if (ret)
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return ret;
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ret = pwm_config(pwm, val, pwm->period);
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return ret ? : size;
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}
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static ssize_t pwm_enable_show(struct device *child,
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struct device_attribute *attr,
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char *buf)
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{
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const struct pwm_device *pwm = child_to_pwm_device(child);
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int enabled = test_bit(PWMF_ENABLED, &pwm->flags);
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return sprintf(buf, "%d\n", enabled);
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}
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static ssize_t pwm_enable_store(struct device *child,
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struct device_attribute *attr,
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const char *buf, size_t size)
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{
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struct pwm_device *pwm = child_to_pwm_device(child);
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int val, ret;
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ret = kstrtoint(buf, 0, &val);
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if (ret)
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return ret;
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switch (val) {
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case 0:
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pwm_disable(pwm);
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break;
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case 1:
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ret = pwm_enable(pwm);
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break;
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default:
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ret = -EINVAL;
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break;
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}
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return ret ? : size;
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}
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static ssize_t pwm_polarity_show(struct device *child,
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struct device_attribute *attr,
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char *buf)
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{
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const struct pwm_device *pwm = child_to_pwm_device(child);
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return sprintf(buf, "%s\n", pwm->polarity ? "inversed" : "normal");
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}
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static ssize_t pwm_polarity_store(struct device *child,
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struct device_attribute *attr,
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const char *buf, size_t size)
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{
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struct pwm_device *pwm = child_to_pwm_device(child);
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enum pwm_polarity polarity;
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int ret;
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if (sysfs_streq(buf, "normal"))
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polarity = PWM_POLARITY_NORMAL;
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else if (sysfs_streq(buf, "inversed"))
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polarity = PWM_POLARITY_INVERSED;
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else
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return -EINVAL;
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ret = pwm_set_polarity(pwm, polarity);
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return ret ? : size;
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}
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static DEVICE_ATTR(period, 0644, pwm_period_show, pwm_period_store);
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static DEVICE_ATTR(duty_cycle, 0644, pwm_duty_cycle_show, pwm_duty_cycle_store);
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static DEVICE_ATTR(enable, 0644, pwm_enable_show, pwm_enable_store);
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static DEVICE_ATTR(polarity, 0644, pwm_polarity_show, pwm_polarity_store);
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static struct attribute *pwm_attrs[] = {
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&dev_attr_period.attr,
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&dev_attr_duty_cycle.attr,
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&dev_attr_enable.attr,
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&dev_attr_polarity.attr,
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NULL
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};
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static const struct attribute_group pwm_attr_group = {
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.attrs = pwm_attrs,
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};
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static const struct attribute_group *pwm_attr_groups[] = {
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&pwm_attr_group,
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NULL,
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};
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static void pwm_export_release(struct device *child)
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{
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struct pwm_export *export = child_to_pwm_export(child);
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kfree(export);
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}
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static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
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{
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struct pwm_export *export;
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int ret;
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if (test_and_set_bit(PWMF_EXPORTED, &pwm->flags))
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return -EBUSY;
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export = kzalloc(sizeof(*export), GFP_KERNEL);
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if (!export) {
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clear_bit(PWMF_EXPORTED, &pwm->flags);
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return -ENOMEM;
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}
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export->pwm = pwm;
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export->child.release = pwm_export_release;
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export->child.parent = parent;
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export->child.devt = MKDEV(0, 0);
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export->child.groups = pwm_attr_groups;
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dev_set_name(&export->child, "pwm%u", pwm->hwpwm);
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ret = device_register(&export->child);
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if (ret) {
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clear_bit(PWMF_EXPORTED, &pwm->flags);
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kfree(export);
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return ret;
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}
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return 0;
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}
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static int pwm_unexport_match(struct device *child, void *data)
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{
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return child_to_pwm_device(child) == data;
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}
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static int pwm_unexport_child(struct device *parent, struct pwm_device *pwm)
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{
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struct device *child;
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if (!test_and_clear_bit(PWMF_EXPORTED, &pwm->flags))
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return -ENODEV;
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child = device_find_child(parent, pwm, pwm_unexport_match);
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if (!child)
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return -ENODEV;
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/* for device_find_child() */
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put_device(child);
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device_unregister(child);
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pwm_put(pwm);
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return 0;
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}
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static ssize_t pwm_export_store(struct device *parent,
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struct device_attribute *attr,
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const char *buf, size_t len)
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{
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struct pwm_chip *chip = dev_get_drvdata(parent);
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struct pwm_device *pwm;
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unsigned int hwpwm;
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int ret;
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ret = kstrtouint(buf, 0, &hwpwm);
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if (ret < 0)
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return ret;
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if (hwpwm >= chip->npwm)
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return -ENODEV;
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|
||||
pwm = pwm_request_from_chip(chip, hwpwm, "sysfs");
|
||||
if (IS_ERR(pwm))
|
||||
return PTR_ERR(pwm);
|
||||
|
||||
ret = pwm_export_child(parent, pwm);
|
||||
if (ret < 0)
|
||||
pwm_put(pwm);
|
||||
|
||||
return ret ? : len;
|
||||
}
|
||||
|
||||
static ssize_t pwm_unexport_store(struct device *parent,
|
||||
struct device_attribute *attr,
|
||||
const char *buf, size_t len)
|
||||
{
|
||||
struct pwm_chip *chip = dev_get_drvdata(parent);
|
||||
unsigned int hwpwm;
|
||||
int ret;
|
||||
|
||||
ret = kstrtouint(buf, 0, &hwpwm);
|
||||
if (ret < 0)
|
||||
return ret;
|
||||
|
||||
if (hwpwm >= chip->npwm)
|
||||
return -ENODEV;
|
||||
|
||||
ret = pwm_unexport_child(parent, &chip->pwms[hwpwm]);
|
||||
|
||||
return ret ? : len;
|
||||
}
|
||||
|
||||
static ssize_t pwm_npwm_show(struct device *parent,
|
||||
struct device_attribute *attr,
|
||||
char *buf)
|
||||
{
|
||||
const struct pwm_chip *chip = dev_get_drvdata(parent);
|
||||
|
||||
return sprintf(buf, "%u\n", chip->npwm);
|
||||
}
|
||||
|
||||
static struct device_attribute pwm_chip_attrs[] = {
|
||||
__ATTR(export, 0200, NULL, pwm_export_store),
|
||||
__ATTR(unexport, 0200, NULL, pwm_unexport_store),
|
||||
__ATTR(npwm, 0444, pwm_npwm_show, NULL),
|
||||
__ATTR_NULL,
|
||||
};
|
||||
|
||||
static struct class pwm_class = {
|
||||
.name = "pwm",
|
||||
.owner = THIS_MODULE,
|
||||
.dev_attrs = pwm_chip_attrs,
|
||||
};
|
||||
|
||||
static int pwmchip_sysfs_match(struct device *parent, const void *data)
|
||||
{
|
||||
return dev_get_drvdata(parent) == data;
|
||||
}
|
||||
|
||||
void pwmchip_sysfs_export(struct pwm_chip *chip)
|
||||
{
|
||||
struct device *parent;
|
||||
|
||||
/*
|
||||
* If device_create() fails the pwm_chip is still usable by
|
||||
* the kernel its just not exported.
|
||||
*/
|
||||
parent = device_create(&pwm_class, chip->dev, MKDEV(0, 0), chip,
|
||||
"pwmchip%d", chip->base);
|
||||
if (IS_ERR(parent)) {
|
||||
dev_warn(chip->dev,
|
||||
"device_create failed for pwm_chip sysfs export\n");
|
||||
}
|
||||
}
|
||||
|
||||
void pwmchip_sysfs_unexport(struct pwm_chip *chip)
|
||||
{
|
||||
struct device *parent;
|
||||
|
||||
parent = class_find_device(&pwm_class, NULL, chip,
|
||||
pwmchip_sysfs_match);
|
||||
if (parent) {
|
||||
/* for class_find_device() */
|
||||
put_device(parent);
|
||||
device_unregister(parent);
|
||||
}
|
||||
}
|
||||
|
||||
static int __init pwm_sysfs_init(void)
|
||||
{
|
||||
return class_register(&pwm_class);
|
||||
}
|
||||
subsys_initcall(pwm_sysfs_init);
|
||||
|
|
@ -76,6 +76,7 @@ enum pwm_polarity {
|
|||
enum {
|
||||
PWMF_REQUESTED = 1 << 0,
|
||||
PWMF_ENABLED = 1 << 1,
|
||||
PWMF_EXPORTED = 1 << 2,
|
||||
};
|
||||
|
||||
struct pwm_device {
|
||||
|
|
@ -86,7 +87,9 @@ struct pwm_device {
|
|||
struct pwm_chip *chip;
|
||||
void *chip_data;
|
||||
|
||||
unsigned int period; /* in nanoseconds */
|
||||
unsigned int period; /* in nanoseconds */
|
||||
unsigned int duty_cycle; /* in nanoseconds */
|
||||
enum pwm_polarity polarity;
|
||||
};
|
||||
|
||||
static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
|
||||
|
|
@ -100,6 +103,17 @@ static inline unsigned int pwm_get_period(struct pwm_device *pwm)
|
|||
return pwm ? pwm->period : 0;
|
||||
}
|
||||
|
||||
static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
|
||||
{
|
||||
if (pwm)
|
||||
pwm->duty_cycle = duty;
|
||||
}
|
||||
|
||||
static inline unsigned int pwm_get_duty_cycle(struct pwm_device *pwm)
|
||||
{
|
||||
return pwm ? pwm->duty_cycle : 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* pwm_set_polarity - configure the polarity of a PWM signal
|
||||
*/
|
||||
|
|
@ -278,4 +292,17 @@ static inline void pwm_add_table(struct pwm_lookup *table, size_t num)
|
|||
}
|
||||
#endif
|
||||
|
||||
#ifdef CONFIG_PWM_SYSFS
|
||||
void pwmchip_sysfs_export(struct pwm_chip *chip);
|
||||
void pwmchip_sysfs_unexport(struct pwm_chip *chip);
|
||||
#else
|
||||
static inline void pwmchip_sysfs_export(struct pwm_chip *chip)
|
||||
{
|
||||
}
|
||||
|
||||
static inline void pwmchip_sysfs_unexport(struct pwm_chip *chip)
|
||||
{
|
||||
}
|
||||
#endif /* CONFIG_PWM_SYSFS */
|
||||
|
||||
#endif /* __LINUX_PWM_H */
|
||||
|
|
|
|||
Loading…
Reference in New Issue