Commit ff5430de authored by Guennadi Liakhovetski's avatar Guennadi Liakhovetski Committed by Mauro Carvalho Chehab
Browse files

[media] V4L2: add temporary clock helpers 



Typical video devices like camera sensors require an external clock source.
Many such devices cannot even access their hardware registers without a
running clock. These clock sources should be controlled by their consumers.
This should be performed, using the generic clock framework. Unfortunately
so far only very few systems have been ported to that framework. This patch
adds a set of temporary helpers, mimicking the generic clock API, to V4L2.
Platforms, adopting the clock API, should switch to using it. Eventually
this temporary API should be removed.

Signed-off-by: default avatarGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Acked-by: default avatarLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 812e8b22

drivers/media/v4l2-core/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
tuner-objs	:=	tuner-core.o



videodev-objs	:=	v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o \

			v4l2-event.o v4l2-ctrls.o v4l2-subdev.o

			v4l2-event.o v4l2-ctrls.o v4l2-subdev.o v4l2-clk.o

ifeq ($(CONFIG_COMPAT),y)

  videodev-objs += v4l2-compat-ioctl32.o

endif

drivers/media/v4l2-core/v4l2-clk.c

0 → 100644
+242 −0
Original line number Diff line number Diff line 
/*

 * V4L2 clock service

 *

 * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */



#include <linux/atomic.h>

#include <linux/device.h>

#include <linux/errno.h>

#include <linux/list.h>

#include <linux/module.h>

#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/string.h>



#include <media/v4l2-clk.h>

#include <media/v4l2-subdev.h>



static DEFINE_MUTEX(clk_lock);

static LIST_HEAD(clk_list);



static struct v4l2_clk *v4l2_clk_find(const char *dev_id, const char *id)

{

	struct v4l2_clk *clk;



	list_for_each_entry(clk, &clk_list, list) {

		if (strcmp(dev_id, clk->dev_id))

			continue;



		if (!id || !clk->id || !strcmp(clk->id, id))

			return clk;

	}



	return ERR_PTR(-ENODEV);

}



struct v4l2_clk *v4l2_clk_get(struct device *dev, const char *id)

{

	struct v4l2_clk *clk;



	mutex_lock(&clk_lock);

	clk = v4l2_clk_find(dev_name(dev), id);



	if (!IS_ERR(clk))

		atomic_inc(&clk->use_count);

	mutex_unlock(&clk_lock);



	return clk;

}

EXPORT_SYMBOL(v4l2_clk_get);



void v4l2_clk_put(struct v4l2_clk *clk)

{

	struct v4l2_clk *tmp;



	if (IS_ERR(clk))

		return;



	mutex_lock(&clk_lock);



	list_for_each_entry(tmp, &clk_list, list)

		if (tmp == clk)

			atomic_dec(&clk->use_count);



	mutex_unlock(&clk_lock);

}

EXPORT_SYMBOL(v4l2_clk_put);



static int v4l2_clk_lock_driver(struct v4l2_clk *clk)

{

	struct v4l2_clk *tmp;

	int ret = -ENODEV;



	mutex_lock(&clk_lock);



	list_for_each_entry(tmp, &clk_list, list)

		if (tmp == clk) {

			ret = !try_module_get(clk->ops->owner);

			if (ret)

				ret = -EFAULT;

			break;

		}



	mutex_unlock(&clk_lock);



	return ret;

}



static void v4l2_clk_unlock_driver(struct v4l2_clk *clk)

{

	module_put(clk->ops->owner);

}



int v4l2_clk_enable(struct v4l2_clk *clk)

{

	int ret = v4l2_clk_lock_driver(clk);



	if (ret < 0)

		return ret;



	mutex_lock(&clk->lock);



	if (++clk->enable == 1 && clk->ops->enable) {

		ret = clk->ops->enable(clk);

		if (ret < 0)

			clk->enable--;

	}



	mutex_unlock(&clk->lock);



	return ret;

}

EXPORT_SYMBOL(v4l2_clk_enable);



/*

 * You might Oops if you try to disabled a disabled clock, because then the

 * driver isn't locked and could have been unloaded by now, so, don't do that

 */

void v4l2_clk_disable(struct v4l2_clk *clk)

{

	int enable;



	mutex_lock(&clk->lock);



	enable = --clk->enable;

	if (WARN(enable < 0, "Unbalanced %s() on %s:%s!\n", __func__,

		 clk->dev_id, clk->id))

		clk->enable++;

	else if (!enable && clk->ops->disable)

		clk->ops->disable(clk);



	mutex_unlock(&clk->lock);



	v4l2_clk_unlock_driver(clk);

}

EXPORT_SYMBOL(v4l2_clk_disable);



unsigned long v4l2_clk_get_rate(struct v4l2_clk *clk)

{

	int ret = v4l2_clk_lock_driver(clk);



	if (ret < 0)

		return ret;



	mutex_lock(&clk->lock);

	if (!clk->ops->get_rate)

		ret = -ENOSYS;

	else

		ret = clk->ops->get_rate(clk);

	mutex_unlock(&clk->lock);



	v4l2_clk_unlock_driver(clk);



	return ret;

}

EXPORT_SYMBOL(v4l2_clk_get_rate);



int v4l2_clk_set_rate(struct v4l2_clk *clk, unsigned long rate)

{

	int ret = v4l2_clk_lock_driver(clk);



	if (ret < 0)

		return ret;



	mutex_lock(&clk->lock);

	if (!clk->ops->set_rate)

		ret = -ENOSYS;

	else

		ret = clk->ops->set_rate(clk, rate);

	mutex_unlock(&clk->lock);



	v4l2_clk_unlock_driver(clk);



	return ret;

}

EXPORT_SYMBOL(v4l2_clk_set_rate);



struct v4l2_clk *v4l2_clk_register(const struct v4l2_clk_ops *ops,

				   const char *dev_id,

				   const char *id, void *priv)

{

	struct v4l2_clk *clk;

	int ret;



	if (!ops || !dev_id)

		return ERR_PTR(-EINVAL);



	clk = kzalloc(sizeof(struct v4l2_clk), GFP_KERNEL);

	if (!clk)

		return ERR_PTR(-ENOMEM);



	clk->id = kstrdup(id, GFP_KERNEL);

	clk->dev_id = kstrdup(dev_id, GFP_KERNEL);

	if ((id && !clk->id) || !clk->dev_id) {

		ret = -ENOMEM;

		goto ealloc;

	}

	clk->ops = ops;

	clk->priv = priv;

	atomic_set(&clk->use_count, 0);

	mutex_init(&clk->lock);



	mutex_lock(&clk_lock);

	if (!IS_ERR(v4l2_clk_find(dev_id, id))) {

		mutex_unlock(&clk_lock);

		ret = -EEXIST;

		goto eexist;

	}

	list_add_tail(&clk->list, &clk_list);

	mutex_unlock(&clk_lock);



	return clk;



eexist:

ealloc:

	kfree(clk->id);

	kfree(clk->dev_id);

	kfree(clk);

	return ERR_PTR(ret);

}

EXPORT_SYMBOL(v4l2_clk_register);



void v4l2_clk_unregister(struct v4l2_clk *clk)

{

	if (WARN(atomic_read(&clk->use_count),

		 "%s(): Refusing to unregister ref-counted %s:%s clock!\n",

		 __func__, clk->dev_id, clk->id))

		return;



	mutex_lock(&clk_lock);

	list_del(&clk->list);

	mutex_unlock(&clk_lock);



	kfree(clk->id);

	kfree(clk->dev_id);

	kfree(clk);

}

EXPORT_SYMBOL(v4l2_clk_unregister);

include/media/v4l2-clk.h

0 → 100644
+54 −0
Original line number Diff line number Diff line 
/*

 * V4L2 clock service

 *

 * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@gmx.de>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 *

 * ATTENTION: This is a temporary API and it shall be replaced by the generic

 * clock API, when the latter becomes widely available.

 */



#ifndef MEDIA_V4L2_CLK_H

#define MEDIA_V4L2_CLK_H



#include <linux/atomic.h>

#include <linux/list.h>

#include <linux/mutex.h>



struct module;

struct device;



struct v4l2_clk {

	struct list_head list;

	const struct v4l2_clk_ops *ops;

	const char *dev_id;

	const char *id;

	int enable;

	struct mutex lock; /* Protect the enable count */

	atomic_t use_count;

	void *priv;

};



struct v4l2_clk_ops {

	struct module	*owner;

	int		(*enable)(struct v4l2_clk *clk);

	void		(*disable)(struct v4l2_clk *clk);

	unsigned long	(*get_rate)(struct v4l2_clk *clk);

	int		(*set_rate)(struct v4l2_clk *clk, unsigned long);

};



struct v4l2_clk *v4l2_clk_register(const struct v4l2_clk_ops *ops,

				   const char *dev_name,

				   const char *name, void *priv);

void v4l2_clk_unregister(struct v4l2_clk *clk);

struct v4l2_clk *v4l2_clk_get(struct device *dev, const char *id);

void v4l2_clk_put(struct v4l2_clk *clk);

int v4l2_clk_enable(struct v4l2_clk *clk);

void v4l2_clk_disable(struct v4l2_clk *clk);

unsigned long v4l2_clk_get_rate(struct v4l2_clk *clk);

int v4l2_clk_set_rate(struct v4l2_clk *clk, unsigned long rate);



#endif

CRA Git | Maintained and supported by SUSTech CRA and CCSE