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    Subject[PATCHv2 1/7] pwm: Add pwm core driver
    Date
    The existing pwm based led and backlight driver makes use of the
    pwm(include/linux/pwm.h). So all the board specific pwm drivers will
    be exposing the same set of function name as in include/linux/pwm.h.
    Consder a platform with multi Soc or having more than one pwm module, in
    such a case, there exists more than one pwm driver for a platform. Each
    of these pwm drivers export the same set of function and hence leads to
    re-declaration build error.

    In order to overcome this issue all the pwm drivers must register to
    some core pwm driver with function pointers for pwm operations (i.e
    pwm_config, pwm_enable, pwm_disable).

    The clients of pwm device will have to call pwm_request, wherein
    they will get the pointer to struct pwm_ops. This structure include
    function pointers for pwm_config, pwm_enable and pwm_disable.

    Signed-off-by: Arun Murthy <arun.murthy@stericsson.com>
    Acked-by: Linus Walleij <linus.walleij@stericsson.com>
    ---
    drivers/Kconfig | 2 +
    drivers/Makefile | 1 +
    drivers/pwm/Kconfig | 18 ++++++
    drivers/pwm/Makefile | 1 +
    drivers/pwm/pwm-core.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/pwm.h | 12 ++++-
    6 files changed, 168 insertions(+), 1 deletions(-)
    create mode 100644 drivers/pwm/Kconfig
    create mode 100644 drivers/pwm/Makefile
    create mode 100644 drivers/pwm/pwm-core.c

    diff --git a/drivers/Kconfig b/drivers/Kconfig
    index a2b902f..e042f27 100644
    --- a/drivers/Kconfig
    +++ b/drivers/Kconfig
    @@ -111,4 +111,6 @@ source "drivers/xen/Kconfig"
    source "drivers/staging/Kconfig"

    source "drivers/platform/Kconfig"
    +
    +source "drivers/pwm/Kconfig"
    endmenu
    diff --git a/drivers/Makefile b/drivers/Makefile
    index 4ca727d..0061ec4 100644
    --- a/drivers/Makefile
    +++ b/drivers/Makefile
    @@ -116,3 +116,4 @@ obj-$(CONFIG_STAGING) += staging/
    obj-y += platform/
    obj-y += ieee802154/
    obj-y += vbus/
    +obj-$(CONFIG_PWM_DEVICES) += pwm/
    diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
    new file mode 100644
    index 0000000..03a9813
    --- /dev/null
    +++ b/drivers/pwm/Kconfig
    @@ -0,0 +1,18 @@
    +#
    +# PWM devices
    +#
    +
    +menuconfig PWM_DEVICES
    + bool "PWM devices"
    + default y
    + ---help---
    + Say Y to enable pwm core driver and see options for various pwm
    + drivers. This option enables pwm drivers to register with the
    + pwm core driver and thereby provide a single interface to the
    + clients using PWM.
    +
    + If you say N, all options in this submenu will be skipped and disabled.
    +
    +if PWM_DEVICES
    +
    +endif # PWM_DEVICES
    diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
    new file mode 100644
    index 0000000..552f969
    --- /dev/null
    +++ b/drivers/pwm/Makefile
    @@ -0,0 +1 @@
    +obj-$(CONFIG_PWM_DEVICES) += pwm-core.o
    diff --git a/drivers/pwm/pwm-core.c b/drivers/pwm/pwm-core.c
    new file mode 100644
    index 0000000..6c6f6a6
    --- /dev/null
    +++ b/drivers/pwm/pwm-core.c
    @@ -0,0 +1,135 @@
    +/*
    + * Copyright (C) ST-Ericsson SA 2010
    + *
    + * License Terms: GNU General Public License v2
    + * Author: Arun R Murthy <arun.murthy@stericsson.com>
    + */
    +#include <linux/init.h>
    +#include <linux/device.h>
    +#include <linux/slab.h>
    +#include <linux/rwsem.h>
    +#include <linux/err.h>
    +#include <linux/pwm.h>
    +
    +struct pwm_device {
    + struct pwm_ops *pops;
    + int pwm_id;
    +};
    +
    +struct pwm_dev_info {
    + struct pwm_device *pwm_dev;
    + struct list_head list;
    +};
    +static struct pwm_dev_info *di;
    +
    +DECLARE_RWSEM(pwm_list_lock);
    +
    +void __deprecated pwm_free(struct pwm_device *pwm)
    +{
    +}
    +
    +int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
    +{
    + if (!pwm->pops)
    + -EFAULT;
    + return pwm->pops->pwm_config(pwm, duty_ns, period_ns);
    +}
    +EXPORT_SYMBOL(pwm_config);
    +
    +int pwm_enable(struct pwm_device *pwm)
    +{
    + if (!pwm->pops)
    + -EFAULT;
    + return pwm->pops->pwm_enable(pwm);
    +}
    +EXPORT_SYMBOL(pwm_enable);
    +
    +void pwm_disable(struct pwm_device *pwm)
    +{
    + if (!pwm->pops)
    + -EFAULT;
    + pwm->pops->pwm_disable(pwm);
    +}
    +EXPORT_SYMBOL(pwm_disable);
    +
    +int pwm_device_register(struct pwm_device *pwm_dev)
    +{
    + struct pwm_dev_info *pwm;
    +
    + down_write(&pwm_list_lock);
    + pwm = kzalloc(sizeof(struct pwm_dev_info), GFP_KERNEL);
    + if (!pwm) {
    + up_write(&pwm_list_lock);
    + return -ENOMEM;
    + }
    + pwm->pwm_dev = pwm_dev;
    + list_add_tail(&pwm->list, &di->list);
    + up_write(&pwm_list_lock);
    +
    + return 0;
    +}
    +EXPORT_SYMBOL(pwm_device_register);
    +
    +int pwm_device_unregister(struct pwm_device *pwm_dev)
    +{
    + struct pwm_dev_info *tmp;
    + struct list_head *pos, *tmp_lst;
    +
    + down_write(&pwm_list_lock);
    + list_for_each_safe(pos, tmp_lst, &di->list) {
    + tmp = list_entry(pos, struct pwm_dev_info, list);
    + if (tmp->pwm_dev == pwm_dev) {
    + list_del(pos);
    + kfree(tmp);
    + up_write(&pwm_list_lock);
    + return 0;
    + }
    + }
    + up_write(&pwm_list_lock);
    + return -ENOENT;
    +}
    +EXPORT_SYMBOL(pwm_device_unregister);
    +
    +struct pwm_device *pwm_request(int pwm_id, const char *name)
    +{
    + struct pwm_dev_info *pwm;
    + struct list_head *pos;
    +
    + down_read(&pwm_list_lock);
    + list_for_each(pos, &di->list) {
    + pwm = list_entry(pos, struct pwm_dev_info, list);
    + if ((!strcmp(pwm->pwm_dev->pops->name, name)) &&
    + (pwm->pwm_dev->pwm_id == pwm_id)) {
    + up_read(&pwm_list_lock);
    + return pwm->pwm_dev;
    + }
    + }
    + up_read(&pwm_list_lock);
    + return ERR_PTR(-ENOENT);
    +}
    +EXPORT_SYMBOL(pwm_request);
    +
    +static int __init pwm_init(void)
    +{
    + struct pwm_dev_info *pwm;
    +
    + pwm = kzalloc(sizeof(struct pwm_dev_info), GFP_KERNEL);
    + if (!pwm)
    + return -ENOMEM;
    + INIT_LIST_HEAD(&pwm->list);
    + di = pwm;
    + return 0;
    +}
    +subsys_initcall(pwm_init);
    +
    +static void __exit pwm_exit(void)
    +{
    + kfree(di);
    +}
    +
    +module_exit(pwm_exit);
    +
    +MODULE_LICENSE("GPL v2");
    +MODULE_AUTHOR("Arun R Murthy");
    +MODULE_ALIAS("core:pwm");
    +MODULE_DESCRIPTION("Core pwm driver");
    diff --git a/include/linux/pwm.h b/include/linux/pwm.h
    index 7c77575..6e7da1f 100644
    --- a/include/linux/pwm.h
    +++ b/include/linux/pwm.h
    @@ -3,6 +3,13 @@

    struct pwm_device;

    +struct pwm_ops {
    + int (*pwm_config)(struct pwm_device *pwm, int duty_ns, int period_ns);
    + int (*pwm_enable)(struct pwm_device *pwm);
    + int (*pwm_disable)(struct pwm_device *pwm);
    + char *name;
    +};
    +
    /*
    * pwm_request - request a PWM device
    */
    @@ -11,7 +18,7 @@ struct pwm_device *pwm_request(int pwm_id, const char *label);
    /*
    * pwm_free - free a PWM device
    */
    -void pwm_free(struct pwm_device *pwm);
    +void __deprecated pwm_free(struct pwm_device *pwm);

    /*
    * pwm_config - change a PWM device configuration
    @@ -28,4 +35,7 @@ int pwm_enable(struct pwm_device *pwm);
    */
    void pwm_disable(struct pwm_device *pwm);

    +int pwm_device_register(struct pwm_device *pwm_dev);
    +int pwm_device_unregister(struct pwm_device *pwm_dev);
    +
    #endif /* __LINUX_PWM_H */
    --
    1.7.2.dirty


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