[PATCH 1/3] Driver for user access to internal clocks

[PATCH 1/3] Driver for user access to internal clocks

[Davide Rizzo]

This driver is for user level programs to interact with system clocks.
It allows to read and modify rates and parents, using virtual files.
It requires the implementation of 2 additional functions in the clk interface:
 clk_for_each() and clk_name().
Actually I implemented that functions only for Samsung S3C24xx platform.

Signed-off-by: Davide Rizzo <elpa-rizzo@gmail.com>
---
diff -urNp linux-2.6.28/drivers/uio/clock.c
linux-2.6.28.elpa/drivers/uio/clock.c
--- linux-2.6.28/drivers/uio/clock.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.28.elpa/drivers/uio/clock.c	2009-01-07 18:52:09.000000000 +0100
@@ -0,0 +1,313 @@
+/*
+ driver/misc/clock.c
+
+ Written Feb 2008 by Davide Rizzo <davide@elpa.it>
+
+ This driver allows to read and modify internal clocks' rates using
+  virtual files. User can also read and modify parents.
+
+ This driver requires implementation of clk_name() and clk_enum() functions
+  in architecture specific clock.c
+
+ 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 <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+
+struct clk_info {
+	struct mutex mutex;
+	struct list_head head;
+	struct device *dev;	/* here because needed by create_clock_attr */
+	int count;
+};
+
+struct attr {
+	struct list_head list;
+	struct device_attribute at;
+};
+
+static ssize_t clk_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	unsigned long rate;
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk = clk_get(dev, attr->attr.name);
+
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	rate = 0;
+
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		rate = clk_get_rate(clk);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+
+	}
+	if (snprintf(buffer, PAGE_SIZE, "%ld\n", rate) > PAGE_SIZE)
+		buffer[PAGE_SIZE - 1] = '\0';
+	return strlen(buffer);
+}
+
+static ssize_t clk_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	unsigned long rate;
+	struct clk *clk;
+	int err = strict_strtoul(buffer, 10, &rate);
+
+	if (err)
+		return err;
+
+	clk = clk_get(dev, attr->attr.name);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	mutex_lock(&info->mutex);
+
+	if (rate != 0) {
+		clk_set_rate(clk, clk_round_rate(clk, rate));
+		clk_enable(clk);
+	} else
+		clk_disable(clk);
+
+	mutex_unlock(&info->mutex);
+
+	clk_put(clk);
+
+	return count;
+}
+
+static ssize_t clk_parent_show(struct device *dev,
+	struct device_attribute *attr, char *buffer)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk, *parent;
+	char *s = kstrdup(attr->attr.name, GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+	s[strlen(attr->attr.name) - 7] = '\0';
+	clk = clk_get(dev, s);
+	kfree(s);
+	buffer[0] = '\0';
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		parent = clk_get_parent(clk);
+		if (parent && !IS_ERR(parent)) {
+			const char *full_name = clk_get_name(parent);
+			if (IS_ERR(full_name)) {
+				mutex_unlock(&info->mutex);
+				return PTR_ERR(full_name);
+			}
+			strlcpy(buffer, full_name, PAGE_SIZE);
+			kfree(full_name);
+		}
+		strlcat(buffer, "\n", PAGE_SIZE);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+	}
+	return strlen(buffer);
+}
+
+static ssize_t clk_parent_store(struct device *dev,
+	struct device_attribute *attr, const char *buffer, size_t count)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk, *parent;
+	char *s;
+
+	parent = clk_get(dev, buffer);
+	if (IS_ERR(parent))
+		return PTR_ERR(parent);
+
+	s = kstrdup(attr->attr.name, GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+	s[strlen(attr->attr.name) - 7] = '\0';
+	clk = clk_get(dev, s);
+	kfree(s);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		clk_set_parent(clk, parent);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+	}
+	clk_put(parent);
+	return count;
+}
+
+static int remove_driver(struct platform_device *pdev)
+{
+	struct clk_info *info = platform_get_drvdata(pdev);
+	struct attr *atp;
+
+	mutex_lock(&info->mutex);
+
+	/* Remove all virtual files */
+	while (!list_empty(&info->head)) {
+		atp = list_first_entry(&info->head, struct attr, list);
+		device_remove_file(&pdev->dev, &atp->at);
+		kfree(atp->at.attr.name);
+		list_del(&atp->list);
+		kfree(atp);
+	}
+	platform_set_drvdata(pdev, NULL);
+
+	mutex_unlock(&info->mutex);
+
+	kfree(info);
+	dev_notice(&pdev->dev, "removed\n");
+	return 0;
+}
+
+static int create_clock_attr(struct clk *clk, void *data)
+{
+	struct attr *atp;
+	int err, len;
+	struct clk_info *info = data;
+	const char *name = clk_get_name(clk);
+
+	/* Retrieve clock's name */
+	if (name == NULL || IS_ERR(name)) {
+		/* Don't return error, simply skip this one */
+		dev_err(info->dev, "invalid clock's name\n");
+		return PTR_ERR(name);
+	}
+
+	/* Create rate virtual file */
+	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
+	if (!atp) {
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.attr.mode = S_IRUGO | S_IWUSR;
+	atp->at.attr.name = kstrdup(name, GFP_KERNEL);
+	if (!atp->at.attr.name) {
+		kfree(atp);
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.show = clk_show;
+	atp->at.store = clk_store;
+	err = device_create_file(info->dev, &atp->at);
+	if (err) {
+		kfree(atp->at.attr.name);
+		kfree(atp);
+		dev_err(info->dev, "failed to create file\n");
+		return err;
+	}
+	list_add(&atp->list, &info->head);
+
+	/* Create parent virtual file */
+	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
+	if (!atp) {
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.attr.mode = S_IRUGO | S_IWUSR;
+	len = strlen(name) + 8;
+	atp->at.attr.name = kmalloc(len, GFP_KERNEL);
+	if (!atp->at.attr.name) {
+		kfree(atp);
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	strlcpy((char *)atp->at.attr.name, name, len);
+	strlcat((char *)atp->at.attr.name, "-parent", len);
+	atp->at.show = clk_parent_show;
+	atp->at.store = clk_parent_store;
+	err = device_create_file(info->dev, &atp->at);
+	if (err) {
+		kfree(atp->at.attr.name);
+		kfree(atp);
+		dev_err(info->dev, "failed to create file\n");
+		return err;
+	}
+	list_add(&atp->list, &info->head);
+
+	info->count++;
+	return 0;
+}
+
+static int probe_driver(struct platform_device *pdev)
+{
+	struct clk_info *info;
+	int err;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		dev_err(&pdev->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	mutex_init(&info->mutex);
+	INIT_LIST_HEAD(&info->head);
+	info->dev = &pdev->dev;
+	platform_set_drvdata(pdev, info);
+	err = clk_for_each(create_clock_attr, info);
+	if (err)
+		remove_driver(pdev);
+	else
+		dev_notice(&pdev->dev, "probed OK - %d clocks recognized\n",
+			info->count);
+	return err;
+}
+
+static struct platform_driver driver = {
+	.probe  = probe_driver,
+	.remove = remove_driver,
+	.driver = {
+		.name = "clocks",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init clk_init_module(void)
+{
+	return platform_driver_register(&driver);
+}
+
+static void __exit clk_cleanup_module(void)
+{
+	platform_driver_unregister(&driver);
+}
+
+module_init(clk_init_module);
+module_exit(clk_cleanup_module);
+
+MODULE_AUTHOR("Davide Rizzo <davide@elpa.it>");
+MODULE_DESCRIPTION("Clock driver");
+MODULE_SUPPORTED_DEVICE("clocks");
+MODULE_LICENSE("GPL");
diff -urNp linux-2.6.28/drivers/uio/Kconfig
linux-2.6.28.elpa/drivers/uio/Kconfig
--- linux-2.6.28/drivers/uio/Kconfig	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/uio/Kconfig	2009-01-07 18:58:10.000000000 +0100
@@ -13,6 +13,18 @@ menuconfig UIO

 if UIO

+
+config UIO_CLOCK
+	tristate "General purpose clock driver"
+	default y
+	---help---
+	  This driver allows to configure and control internal clocks'
+	   rates and parents through virtual files.
+	  This driver requires implementation of some additional functions
+	   in architecture specific low-level drivers:
+	   clk_for_each() and clk_get_name()
+	  Currently they're implemented only on Samsung S3C24xx platforms.
+
 config UIO_CIF
 	tristate "generic Hilscher CIF Card driver"
 	depends on PCI
diff -urNp linux-2.6.28/drivers/uio/Makefile
linux-2.6.28.elpa/drivers/uio/Makefile
--- linux-2.6.28/drivers/uio/Makefile	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/uio/Makefile	2009-01-06 18:20:17.000000000 +0100
@@ -1,4 +1,5 @@
 obj-$(CONFIG_UIO)	+= uio.o
+obj-$(CONFIG_UIO_CLOCK) += clock.o
 obj-$(CONFIG_UIO_CIF)	+= uio_cif.o
 obj-$(CONFIG_UIO_PDRV)	+= uio_pdrv.o
 obj-$(CONFIG_UIO_PDRV_GENIRQ)	+= uio_pdrv_genirq.o

Re: [PATCH 1/3] Driver for user access to internal clocks

[Hans J. Koch]

On Thu, Jan 08, 2009 at 10:49:12AM +0100, Davide Rizzo wrote:
> This driver is for user level programs to interact with system clocks.
> It allows to read and modify rates and parents, using virtual files.
> It requires the implementation of 2 additional functions in the clk interface:
>  clk_for_each() and clk_name().
> Actually I implemented that functions only for Samsung S3C24xx platform.
> 
> Signed-off-by: Davide Rizzo <elpa-rizzo@gmail.com>
> ---
> diff -urNp linux-2.6.28/drivers/uio/clock.c
> linux-2.6.28.elpa/drivers/uio/clock.c
> --- linux-2.6.28/drivers/uio/clock.c	1970-01-01 01:00:00.000000000 +0100
> +++ linux-2.6.28.elpa/drivers/uio/clock.c	2009-01-07 18:52:09.000000000 +0100

Davide,
please don't put this in the drivers/uio/ directory. This is no UIO driver.

Thanks,
Hans


> @@ -0,0 +1,313 @@
> +/*
> + driver/misc/clock.c

Ah, it used to have a different place ;-)

> +
> + Written Feb 2008 by Davide Rizzo <davide@elpa.it>
> +
> + This driver allows to read and modify internal clocks' rates using
> +  virtual files. User can also read and modify parents.
> +
> + This driver requires implementation of clk_name() and clk_enum() functions
> +  in architecture specific clock.c
> +
> + 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 <linux/platform_device.h>
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +
> +struct clk_info {
> +	struct mutex mutex;
> +	struct list_head head;
> +	struct device *dev;	/* here because needed by create_clock_attr */
> +	int count;
> +};
> +
> +struct attr {
> +	struct list_head list;
> +	struct device_attribute at;
> +};
> +
> +static ssize_t clk_show(struct device *dev, struct device_attribute *attr,
> +	char *buffer)
> +{
> +	unsigned long rate;
> +	struct clk_info *info = dev_get_drvdata(dev);
> +	struct clk *clk = clk_get(dev, attr->attr.name);
> +
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	rate = 0;
> +
> +	if (!IS_ERR(clk)) {
> +
> +		mutex_lock(&info->mutex);
> +
> +		rate = clk_get_rate(clk);
> +
> +		mutex_unlock(&info->mutex);
> +
> +		clk_put(clk);
> +
> +	}
> +	if (snprintf(buffer, PAGE_SIZE, "%ld\n", rate) > PAGE_SIZE)
> +		buffer[PAGE_SIZE - 1] = '\0';
> +	return strlen(buffer);
> +}
> +
> +static ssize_t clk_store(struct device *dev, struct device_attribute *attr,
> +	const char *buffer, size_t count)
> +{
> +	struct clk_info *info = dev_get_drvdata(dev);
> +	unsigned long rate;
> +	struct clk *clk;
> +	int err = strict_strtoul(buffer, 10, &rate);
> +
> +	if (err)
> +		return err;
> +
> +	clk = clk_get(dev, attr->attr.name);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	mutex_lock(&info->mutex);
> +
> +	if (rate != 0) {
> +		clk_set_rate(clk, clk_round_rate(clk, rate));
> +		clk_enable(clk);
> +	} else
> +		clk_disable(clk);
> +
> +	mutex_unlock(&info->mutex);
> +
> +	clk_put(clk);
> +
> +	return count;
> +}
> +
> +static ssize_t clk_parent_show(struct device *dev,
> +	struct device_attribute *attr, char *buffer)
> +{
> +	struct clk_info *info = dev_get_drvdata(dev);
> +	struct clk *clk, *parent;
> +	char *s = kstrdup(attr->attr.name, GFP_KERNEL);
> +	if (!s)
> +		return -ENOMEM;
> +	s[strlen(attr->attr.name) - 7] = '\0';
> +	clk = clk_get(dev, s);
> +	kfree(s);
> +	buffer[0] = '\0';
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +	if (!IS_ERR(clk)) {
> +
> +		mutex_lock(&info->mutex);
> +
> +		parent = clk_get_parent(clk);
> +		if (parent && !IS_ERR(parent)) {
> +			const char *full_name = clk_get_name(parent);
> +			if (IS_ERR(full_name)) {
> +				mutex_unlock(&info->mutex);
> +				return PTR_ERR(full_name);
> +			}
> +			strlcpy(buffer, full_name, PAGE_SIZE);
> +			kfree(full_name);
> +		}
> +		strlcat(buffer, "\n", PAGE_SIZE);
> +
> +		mutex_unlock(&info->mutex);
> +
> +		clk_put(clk);
> +	}
> +	return strlen(buffer);
> +}
> +
> +static ssize_t clk_parent_store(struct device *dev,
> +	struct device_attribute *attr, const char *buffer, size_t count)
> +{
> +	struct clk_info *info = dev_get_drvdata(dev);
> +	struct clk *clk, *parent;
> +	char *s;
> +
> +	parent = clk_get(dev, buffer);
> +	if (IS_ERR(parent))
> +		return PTR_ERR(parent);
> +
> +	s = kstrdup(attr->attr.name, GFP_KERNEL);
> +	if (!s)
> +		return -ENOMEM;
> +	s[strlen(attr->attr.name) - 7] = '\0';
> +	clk = clk_get(dev, s);
> +	kfree(s);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	if (!IS_ERR(clk)) {
> +
> +		mutex_lock(&info->mutex);
> +
> +		clk_set_parent(clk, parent);
> +
> +		mutex_unlock(&info->mutex);
> +
> +		clk_put(clk);
> +	}
> +	clk_put(parent);
> +	return count;
> +}
> +
> +static int remove_driver(struct platform_device *pdev)
> +{
> +	struct clk_info *info = platform_get_drvdata(pdev);
> +	struct attr *atp;
> +
> +	mutex_lock(&info->mutex);
> +
> +	/* Remove all virtual files */
> +	while (!list_empty(&info->head)) {
> +		atp = list_first_entry(&info->head, struct attr, list);
> +		device_remove_file(&pdev->dev, &atp->at);
> +		kfree(atp->at.attr.name);
> +		list_del(&atp->list);
> +		kfree(atp);
> +	}
> +	platform_set_drvdata(pdev, NULL);
> +
> +	mutex_unlock(&info->mutex);
> +
> +	kfree(info);
> +	dev_notice(&pdev->dev, "removed\n");
> +	return 0;
> +}
> +
> +static int create_clock_attr(struct clk *clk, void *data)
> +{
> +	struct attr *atp;
> +	int err, len;
> +	struct clk_info *info = data;
> +	const char *name = clk_get_name(clk);
> +
> +	/* Retrieve clock's name */
> +	if (name == NULL || IS_ERR(name)) {
> +		/* Don't return error, simply skip this one */
> +		dev_err(info->dev, "invalid clock's name\n");
> +		return PTR_ERR(name);
> +	}
> +
> +	/* Create rate virtual file */
> +	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
> +	if (!atp) {
> +		dev_err(info->dev, "out of kernel memory\n");
> +		return -ENOMEM;
> +	}
> +	atp->at.attr.mode = S_IRUGO | S_IWUSR;
> +	atp->at.attr.name = kstrdup(name, GFP_KERNEL);
> +	if (!atp->at.attr.name) {
> +		kfree(atp);
> +		dev_err(info->dev, "out of kernel memory\n");
> +		return -ENOMEM;
> +	}
> +	atp->at.show = clk_show;
> +	atp->at.store = clk_store;
> +	err = device_create_file(info->dev, &atp->at);
> +	if (err) {
> +		kfree(atp->at.attr.name);
> +		kfree(atp);
> +		dev_err(info->dev, "failed to create file\n");
> +		return err;
> +	}
> +	list_add(&atp->list, &info->head);
> +
> +	/* Create parent virtual file */
> +	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
> +	if (!atp) {
> +		dev_err(info->dev, "out of kernel memory\n");
> +		return -ENOMEM;
> +	}
> +	atp->at.attr.mode = S_IRUGO | S_IWUSR;
> +	len = strlen(name) + 8;
> +	atp->at.attr.name = kmalloc(len, GFP_KERNEL);
> +	if (!atp->at.attr.name) {
> +		kfree(atp);
> +		dev_err(info->dev, "out of kernel memory\n");
> +		return -ENOMEM;
> +	}
> +	strlcpy((char *)atp->at.attr.name, name, len);
> +	strlcat((char *)atp->at.attr.name, "-parent", len);
> +	atp->at.show = clk_parent_show;
> +	atp->at.store = clk_parent_store;
> +	err = device_create_file(info->dev, &atp->at);
> +	if (err) {
> +		kfree(atp->at.attr.name);
> +		kfree(atp);
> +		dev_err(info->dev, "failed to create file\n");
> +		return err;
> +	}
> +	list_add(&atp->list, &info->head);
> +
> +	info->count++;
> +	return 0;
> +}
> +
> +static int probe_driver(struct platform_device *pdev)
> +{
> +	struct clk_info *info;
> +	int err;
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info) {
> +		dev_err(&pdev->dev, "out of kernel memory\n");
> +		return -ENOMEM;
> +	}
> +	mutex_init(&info->mutex);
> +	INIT_LIST_HEAD(&info->head);
> +	info->dev = &pdev->dev;
> +	platform_set_drvdata(pdev, info);
> +	err = clk_for_each(create_clock_attr, info);
> +	if (err)
> +		remove_driver(pdev);
> +	else
> +		dev_notice(&pdev->dev, "probed OK - %d clocks recognized\n",
> +			info->count);
> +	return err;
> +}
> +
> +static struct platform_driver driver = {
> +	.probe  = probe_driver,
> +	.remove = remove_driver,
> +	.driver = {
> +		.name = "clocks",
> +		.owner = THIS_MODULE,
> +	},
> +};
> +
> +static int __init clk_init_module(void)
> +{
> +	return platform_driver_register(&driver);
> +}
> +
> +static void __exit clk_cleanup_module(void)
> +{
> +	platform_driver_unregister(&driver);
> +}
> +
> +module_init(clk_init_module);
> +module_exit(clk_cleanup_module);
> +
> +MODULE_AUTHOR("Davide Rizzo <davide@elpa.it>");
> +MODULE_DESCRIPTION("Clock driver");
> +MODULE_SUPPORTED_DEVICE("clocks");
> +MODULE_LICENSE("GPL");
> diff -urNp linux-2.6.28/drivers/uio/Kconfig
> linux-2.6.28.elpa/drivers/uio/Kconfig
> --- linux-2.6.28/drivers/uio/Kconfig	2008-12-25 00:26:37.000000000 +0100
> +++ linux-2.6.28.elpa/drivers/uio/Kconfig	2009-01-07 18:58:10.000000000 +0100
> @@ -13,6 +13,18 @@ menuconfig UIO
> 
>  if UIO
> 
> +
> +config UIO_CLOCK
> +	tristate "General purpose clock driver"
> +	default y
> +	---help---
> +	  This driver allows to configure and control internal clocks'
> +	   rates and parents through virtual files.
> +	  This driver requires implementation of some additional functions
> +	   in architecture specific low-level drivers:
> +	   clk_for_each() and clk_get_name()
> +	  Currently they're implemented only on Samsung S3C24xx platforms.
> +
>  config UIO_CIF
>  	tristate "generic Hilscher CIF Card driver"
>  	depends on PCI
> diff -urNp linux-2.6.28/drivers/uio/Makefile
> linux-2.6.28.elpa/drivers/uio/Makefile
> --- linux-2.6.28/drivers/uio/Makefile	2008-12-25 00:26:37.000000000 +0100
> +++ linux-2.6.28.elpa/drivers/uio/Makefile	2009-01-06 18:20:17.000000000 +0100
> @@ -1,4 +1,5 @@
>  obj-$(CONFIG_UIO)	+= uio.o
> +obj-$(CONFIG_UIO_CLOCK) += clock.o
>  obj-$(CONFIG_UIO_CIF)	+= uio_cif.o
>  obj-$(CONFIG_UIO_PDRV)	+= uio_pdrv.o
>  obj-$(CONFIG_UIO_PDRV_GENIRQ)	+= uio_pdrv_genirq.o

Re: [PATCH 1/3] Driver for user access to internal clocks

[Davide Rizzo]

> Davide,
> please don't put this in the drivers/uio/ directory. This is no UIO driver.
>
> Thanks,
> Hans
>
Ok, moved to /drivers/misc

This driver is for user level programs to interact with system clocks.
It allows to read and modify rates and parents, using virtual files.
It requires the implementation of 2 additional functions in the clk interface:
 clk_for_each() and clk_name().
Actually I implemented that functions only for Samsung S3C24xx platform.

Signed-off-by: Davide Rizzo <elpa-rizzo@gmail.com>
---
diff -urNp linux-2.6.28/drivers/misc/clock.c
linux-2.6.28.elpa/drivers/misc/clock.c
--- linux-2.6.28/drivers/misc/clock.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/clock.c	2009-01-08 12:24:04.000000000 +0100
@@ -0,0 +1,313 @@
+/*
+ driver/misc/clock.c
+
+ Written Feb 2008 by Davide Rizzo <elpa-rizzo@gmail.com>
+
+ This driver allows to read and modify internal clocks' rates using
+  virtual files. User can also read and modify parents.
+
+ This driver requires implementation of clk_name() and clk_enum() functions
+  in architecture specific clock.c
+
+ 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 <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+
+struct clk_info {
+	struct mutex mutex;
+	struct list_head head;
+	struct device *dev;	/* here because needed by create_clock_attr */
+	int count;
+};
+
+struct attr {
+	struct list_head list;
+	struct device_attribute at;
+};
+
+static ssize_t clk_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	unsigned long rate;
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk = clk_get(dev, attr->attr.name);
+
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	rate = 0;
+
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		rate = clk_get_rate(clk);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+
+	}
+	if (snprintf(buffer, PAGE_SIZE, "%ld\n", rate) > PAGE_SIZE)
+		buffer[PAGE_SIZE - 1] = '\0';
+	return strlen(buffer);
+}
+
+static ssize_t clk_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	unsigned long rate;
+	struct clk *clk;
+	int err = strict_strtoul(buffer, 10, &rate);
+
+	if (err)
+		return err;
+
+	clk = clk_get(dev, attr->attr.name);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	mutex_lock(&info->mutex);
+
+	if (rate != 0) {
+		clk_set_rate(clk, clk_round_rate(clk, rate));
+		clk_enable(clk);
+	} else
+		clk_disable(clk);
+
+	mutex_unlock(&info->mutex);
+
+	clk_put(clk);
+
+	return count;
+}
+
+static ssize_t clk_parent_show(struct device *dev,
+	struct device_attribute *attr, char *buffer)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk, *parent;
+	char *s = kstrdup(attr->attr.name, GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+	s[strlen(attr->attr.name) - 7] = '\0';
+	clk = clk_get(dev, s);
+	kfree(s);
+	buffer[0] = '\0';
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		parent = clk_get_parent(clk);
+		if (parent && !IS_ERR(parent)) {
+			const char *full_name = clk_get_name(parent);
+			if (IS_ERR(full_name)) {
+				mutex_unlock(&info->mutex);
+				return PTR_ERR(full_name);
+			}
+			strlcpy(buffer, full_name, PAGE_SIZE);
+			kfree(full_name);
+		}
+		strlcat(buffer, "\n", PAGE_SIZE);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+	}
+	return strlen(buffer);
+}
+
+static ssize_t clk_parent_store(struct device *dev,
+	struct device_attribute *attr, const char *buffer, size_t count)
+{
+	struct clk_info *info = dev_get_drvdata(dev);
+	struct clk *clk, *parent;
+	char *s;
+
+	parent = clk_get(dev, buffer);
+	if (IS_ERR(parent))
+		return PTR_ERR(parent);
+
+	s = kstrdup(attr->attr.name, GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+	s[strlen(attr->attr.name) - 7] = '\0';
+	clk = clk_get(dev, s);
+	kfree(s);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	if (!IS_ERR(clk)) {
+
+		mutex_lock(&info->mutex);
+
+		clk_set_parent(clk, parent);
+
+		mutex_unlock(&info->mutex);
+
+		clk_put(clk);
+	}
+	clk_put(parent);
+	return count;
+}
+
+static int remove_driver(struct platform_device *pdev)
+{
+	struct clk_info *info = platform_get_drvdata(pdev);
+	struct attr *atp;
+
+	mutex_lock(&info->mutex);
+
+	/* Remove all virtual files */
+	while (!list_empty(&info->head)) {
+		atp = list_first_entry(&info->head, struct attr, list);
+		device_remove_file(&pdev->dev, &atp->at);
+		kfree(atp->at.attr.name);
+		list_del(&atp->list);
+		kfree(atp);
+	}
+	platform_set_drvdata(pdev, NULL);
+
+	mutex_unlock(&info->mutex);
+
+	kfree(info);
+	dev_notice(&pdev->dev, "removed\n");
+	return 0;
+}
+
+static int create_clock_attr(struct clk *clk, void *data)
+{
+	struct attr *atp;
+	int err, len;
+	struct clk_info *info = data;
+	const char *name = clk_get_name(clk);
+
+	/* Retrieve clock's name */
+	if (name == NULL || IS_ERR(name)) {
+		/* Don't return error, simply skip this one */
+		dev_err(info->dev, "invalid clock's name\n");
+		return PTR_ERR(name);
+	}
+
+	/* Create rate virtual file */
+	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
+	if (!atp) {
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.attr.mode = S_IRUGO | S_IWUSR;
+	atp->at.attr.name = kstrdup(name, GFP_KERNEL);
+	if (!atp->at.attr.name) {
+		kfree(atp);
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.show = clk_show;
+	atp->at.store = clk_store;
+	err = device_create_file(info->dev, &atp->at);
+	if (err) {
+		kfree(atp->at.attr.name);
+		kfree(atp);
+		dev_err(info->dev, "failed to create file\n");
+		return err;
+	}
+	list_add(&atp->list, &info->head);
+
+	/* Create parent virtual file */
+	atp = kzalloc(sizeof(struct attr), GFP_KERNEL);
+	if (!atp) {
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	atp->at.attr.mode = S_IRUGO | S_IWUSR;
+	len = strlen(name) + 8;
+	atp->at.attr.name = kmalloc(len, GFP_KERNEL);
+	if (!atp->at.attr.name) {
+		kfree(atp);
+		dev_err(info->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	strlcpy((char *)atp->at.attr.name, name, len);
+	strlcat((char *)atp->at.attr.name, "-parent", len);
+	atp->at.show = clk_parent_show;
+	atp->at.store = clk_parent_store;
+	err = device_create_file(info->dev, &atp->at);
+	if (err) {
+		kfree(atp->at.attr.name);
+		kfree(atp);
+		dev_err(info->dev, "failed to create file\n");
+		return err;
+	}
+	list_add(&atp->list, &info->head);
+
+	info->count++;
+	return 0;
+}
+
+static int probe_driver(struct platform_device *pdev)
+{
+	struct clk_info *info;
+	int err;
+
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info) {
+		dev_err(&pdev->dev, "out of kernel memory\n");
+		return -ENOMEM;
+	}
+	mutex_init(&info->mutex);
+	INIT_LIST_HEAD(&info->head);
+	info->dev = &pdev->dev;
+	platform_set_drvdata(pdev, info);
+	err = clk_for_each(create_clock_attr, info);
+	if (err)
+		remove_driver(pdev);
+	else
+		dev_notice(&pdev->dev, "probed OK - %d clocks recognized\n",
+			info->count);
+	return err;
+}
+
+static struct platform_driver driver = {
+	.probe  = probe_driver,
+	.remove = remove_driver,
+	.driver = {
+		.name = "clocks",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init clk_init_module(void)
+{
+	return platform_driver_register(&driver);
+}
+
+static void __exit clk_cleanup_module(void)
+{
+	platform_driver_unregister(&driver);
+}
+
+module_init(clk_init_module);
+module_exit(clk_cleanup_module);
+
+MODULE_AUTHOR("Davide Rizzo <elpa-rizzo@gmail.com>");
+MODULE_DESCRIPTION("Clock driver");
+MODULE_SUPPORTED_DEVICE("clocks");
+MODULE_LICENSE("GPL");
diff -urNp linux-2.6.28/drivers/misc/Kconfig
linux-2.6.28.elpa/drivers/misc/Kconfig
--- linux-2.6.28/drivers/misc/Kconfig	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/Kconfig	2009-01-08 16:38:49.000000000 +0100
@@ -500,4 +500,15 @@ config SGI_GRU_DEBUG

 source "drivers/misc/c2port/Kconfig"

+config UIO_CLOCK
+	tristate "General purpose clock driver"
+	default y
+	---help---
+	  This driver allows to configure and control internal clocks'
+	   rates and parents through virtual files.
+	  This driver requires implementation of some additional functions
+	   in architecture specific low-level drivers:
+	   clk_for_each() and clk_get_name()
+	  Currently they're implemented only on Samsung S3C24xx platforms.
+
 endif # MISC_DEVICES
diff -urNp linux-2.6.28/drivers/misc/Makefile
linux-2.6.28.elpa/drivers/misc/Makefile
--- linux-2.6.28/drivers/misc/Makefile	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.28.elpa/drivers/misc/Makefile	2009-01-08 16:37:48.000000000 +0100
@@ -3,6 +3,7 @@
#
 obj- := misc.o	# Dummy rule to force built-in.o to be made

+obj-$(CONFIG_UIO_CLOCK) += clock.o
 obj-$(CONFIG_IBM_ASM)		+= ibmasm/
 obj-$(CONFIG_HDPU_FEATURES)	+= hdpuftrs/
 obj-$(CONFIG_ASUS_LAPTOP)	+= asus-laptop.o

Re: [PATCH 1/3] Driver for user access to internal clocks

[Greg KH]

On Thu, Jan 08, 2009 at 05:06:58PM +0100, Davide Rizzo wrote:
> > Davide,
> > please don't put this in the drivers/uio/ directory. This is no UIO driver.
> >
> > Thanks,
> > Hans
> >
> Ok, moved to /drivers/misc
> 
> This driver is for user level programs to interact with system clocks.

Same comments here as for your "timer.c" file:
	- too generic of a name
	- needs proper documentation
	- send any kernel api changes also to linux-api@vger.kernel.org

thanks,

greg k-h

Re: [PATCH 1/3] Driver for user access to internal clocks

[Davide Rizzo]

> Same comments here as for your "timer.c" file:
>        - too generic of a name
>        - needs proper documentation
>        - send any kernel api changes also to linux-api@vger.kernel.org
>
> thanks,
>
> greg k-h
>

This is the modified Samsung S3c implementation for user mode clock driver.

This is a proposal for adding 2 functions to clk interface to allow higher
 level drivers to enumerate and list all clocks, and to modify clk_get
 to accept device specific clk names in the form "name.id"
There is also the implementation for Samsung S3C24xx platform.

Signed-off-by: Davide Rizzo <elpa.rizzo@gmail.com>
---diff -urpN linux-2.6.29-rc2/arch/arm/plat-s3c/clock.c
linux-2.6.29-rc2.elpa/arch/arm/plat-s3c/clock.c
--- linux-2.6.29-rc2/arch/arm/plat-s3c/clock.c	2009-01-17
11:32:38.000000000 +0100
+++ linux-2.6.29-rc2.elpa/arch/arm/plat-s3c/clock.c	2009-01-28
19:32:08.000000000 +0100
@@ -69,11 +69,19 @@ static int clk_null_enable(struct clk *c

 struct clk *clk_get(struct device *dev, const char *id)
 {
+	long idno;
+	char *name = (char *)id;
+	char *dotpos = strrchr(id, '.');
 	struct clk *p;
 	struct clk *clk = ERR_PTR(-ENOENT);
-	int idno;

-	if (dev == NULL || dev->bus != &platform_bus_type)
+	if (dotpos) {
+		int err = strict_strtol(dotpos + 1, 10, &idno);
+		if (err)
+				return ERR_PTR(err);
+		name = kstrdup(id, GFP_KERNEL);
+		name[dotpos - id] = '\0';
+	} else if (dev == NULL || dev->bus != &platform_bus_type)
 		idno = -1;
 	else
 		idno = to_platform_device(dev)->id;
@@ -82,7 +90,7 @@ struct clk *clk_get(struct device *dev,

 	list_for_each_entry(p, &clocks, list) {
 		if (p->id == idno &&
-		    strcmp(id, p->name) == 0 &&
+		    strcmp(name, p->name) == 0 &&
 		    try_module_get(p->owner)) {
 			clk = p;
 			break;
@@ -94,7 +102,7 @@ struct clk *clk_get(struct device *dev,

 	if (IS_ERR(clk)) {
 		list_for_each_entry(p, &clocks, list) {
-			if (p->id == -1 && strcmp(id, p->name) == 0 &&
+			if (p->id == -1 && strcmp(name, p->name) == 0 &&
 			    try_module_get(p->owner)) {
 				clk = p;
 				break;
@@ -103,6 +111,8 @@ struct clk *clk_get(struct device *dev,
 	}

 	spin_unlock(&clocks_lock);
+	if (dotpos)
+		kfree(name);
 	return clk;
 }

@@ -222,6 +232,42 @@ EXPORT_SYMBOL(clk_set_rate);
 EXPORT_SYMBOL(clk_get_parent);
 EXPORT_SYMBOL(clk_set_parent);

+int clk_for_each(int(*fn)(struct clk *, void *), void *data)
+	{
+	struct clk *clk;
+	int ret = 0;
+
+	list_for_each_entry(clk, &clocks, list)
+	{
+		ret = fn(clk, data);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+EXPORT_SYMBOL(clk_for_each);
+
+/* Returned pointer must be deallocated with kfree() */
+const char *clk_get_name(struct clk *clk)
+{
+	char *s;
+	int len;
+
+	if (IS_ERR(clk))
+		return ERR_PTR(-EINVAL);
+
+	len = strlen(clk->name) + 8;
+	s = kmalloc(len, GFP_KERNEL);
+	if (!s)
+		return ERR_PTR(-ENOMEM);
+	if (clk->id == -1)
+		strlcpy(s, clk->name, len);
+	else if (snprintf(s, len, "%s.%d", clk->name, clk->id) > len)
+		s[len - 1] = '\0';
+	return s;
+}
+EXPORT_SYMBOL(clk_get_name);
+
 /* base clocks */

 static int clk_default_setrate(struct clk *clk, unsigned long rate)
diff -urpN linux-2.6.29-rc2/include/linux/clk.h
linux-2.6.29-rc2.elpa/include/linux/clk.h
--- linux-2.6.29-rc2/include/linux/clk.h	2008-12-25 00:26:37.000000000 +0100
+++ linux-2.6.29-rc2.elpa/include/linux/clk.h	2009-01-28
19:21:43.000000000 +0100
@@ -125,4 +125,22 @@ int clk_set_parent(struct clk *clk, stru
  */
 struct clk *clk_get_parent(struct clk *clk);

+/**
+ * clk_for_each - calls fn, iterating between registered clocks
+ * @fn: function to be called, passing each clk structure in 1st argument
+ * @data: 2nd argument to pass to fn function
+ *
+ * Returns 0 or the called fn return code if != 0
+ */
+int clk_for_each(int(*fn)(struct clk *, void *), void *data);
+
+/**
+ * clk_name - get clock name
+ * @clk: clock source
+ *
+ * Returns clock's name that must be deallocated with kfree(), or valid
+ * IS_ERR() condition containing errno.
+ */
+const char *clk_get_name(struct clk *clk);
+
 #endif

Re: [PATCH 1/3] Driver for user access to internal clocks

[Davide Rizzo]

> Same comments here as for your "timer.c" file:
>        - too generic of a name
>        - needs proper documentation
>        - send any kernel api changes also to linux-api@vger.kernel.org
>
> thanks,
>
> greg k-h
>
Here is the modified user mode clock access driver.
I moved it in /drivers/misc and reorganized virtual files under /sys/class/clock

This driver is for user level programs to interact with system clocks.
It allows to read and modify rates and parents, using virtual files.
It requires the implementation of 2 additional functions in the clk interface:
 clk_for_each() and clk_name().
Actually I implemented that functions only for Samsung S3C24xx platform.

Signed-off-by: Davide Rizzo <elpa.rizzo@gmail.com>
---
diff -urpN linux-2.6.29-rc2/drivers/misc/Kconfig
linux-2.6.29-rc2.elpa/drivers/misc/Kconfig
--- linux-2.6.29-rc2/drivers/misc/Kconfig	2009-01-17 11:32:40.000000000 +0100
+++ linux-2.6.29-rc2.elpa/drivers/misc/Kconfig	2009-01-28
19:21:43.000000000 +0100
@@ -232,4 +232,19 @@ config DELL_LAPTOP

 source "drivers/misc/c2port/Kconfig"

+config UM_CLOCK
+	bool "User mode clock driver"
+	depends on SYSFS
+	default n
+	---help---
+	Allows user mode programs to configure and control internal clocks'
+	 rates and parents through virtual files in sysfs.
+	This driver requires implementation of some additional functions
+	 in architecture specific low-level drivers: clk_for_each() and
+	 clk_get_name(). Moreover, it requires clk_get() to recognize the
+	 "name.id" format
+	Currently they're implemented only on Samsung S3C24xx platforms.
+
+	If unsure, say N.
+
 endif # MISC_DEVICES
diff -urpN linux-2.6.29-rc2/drivers/misc/Makefile
linux-2.6.29-rc2.elpa/drivers/misc/Makefile
--- linux-2.6.29-rc2/drivers/misc/Makefile	2009-01-17 11:32:40.000000000 +0100
+++ linux-2.6.29-rc2.elpa/drivers/misc/Makefile	2009-01-28
19:21:43.000000000 +0100
@@ -20,3 +20,4 @@ obj-$(CONFIG_SGI_XP)		+= sgi-xp/
 obj-$(CONFIG_SGI_GRU)		+= sgi-gru/
 obj-$(CONFIG_HP_ILO)		+= hpilo.o
 obj-$(CONFIG_C2PORT)		+= c2port/
+obj-$(CONFIG_UM_CLOCK) += um_clock.o
diff -urpN linux-2.6.29-rc2/drivers/misc/um_clock.c
linux-2.6.29-rc2.elpa/drivers/misc/um_clock.c
--- linux-2.6.29-rc2/drivers/misc/um_clock.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.29-rc2.elpa/drivers/misc/um_clock.c	2009-01-28
19:21:43.000000000 +0100
@@ -0,0 +1,174 @@
+/*
+ driver/misc/clock.c
+
+ Written Feb 2008 by Davide Rizzo <elpa.rizzo@gmail.com>
+
+ This driver allows to read and modify internal clocks' rates using
+  virtual files. User can also read and modify parents.
+
+ This driver requires implementation of clk_name() and clk_enum() functions
+  in architecture specific clock.c
+
+ 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 <linux/device.h>
+#include <linux/clk.h>
+#include <linux/kdev_t.h>
+#include <linux/err.h>
+
+static DEFINE_MUTEX(mutex);
+
+static ssize_t rate_show(struct device *dev, struct device_attribute *attr,
+	char *buffer)
+{
+	unsigned long rate;
+	struct clk *clk;
+
+	clk = dev_get_drvdata(dev);
+	rate = 0;
+
+	mutex_lock(&mutex);
+
+	rate = clk_get_rate(clk);
+
+	mutex_unlock(&mutex);
+
+	return sprintf(buffer, "%ld\n", rate);
+}
+
+static ssize_t rate_store(struct device *dev, struct device_attribute *attr,
+	const char *buffer, size_t count)
+{
+	unsigned long rate;
+	struct clk *clk;
+	int err;
+
+	clk = dev_get_drvdata(dev);
+	err = strict_strtoul(buffer, 10, &rate);
+	if (err)
+		return err;
+
+	mutex_lock(&mutex);
+
+	if (rate != 0) {
+		clk_set_rate(clk, clk_round_rate(clk, rate));
+		clk_enable(clk);
+	} else
+		clk_disable(clk);
+
+	mutex_unlock(&mutex);
+
+	return count;
+}
+
+static ssize_t parent_show(struct device *dev,
+	struct device_attribute *attr, char *buffer)
+{
+	struct clk *parent, *clk;
+
+	clk = dev_get_drvdata(dev);
+
+	mutex_lock(&mutex);
+
+	parent = clk_get_parent(clk);
+	if (parent && !IS_ERR(parent)) {
+		const char *name = clk_get_name(parent);
+		if (IS_ERR(name)) {
+			mutex_unlock(&mutex);
+			return PTR_ERR(name);
+		}
+		strlcpy(buffer, name, PAGE_SIZE);
+	} else
+		buffer[0] = '\0';
+	strlcat(buffer, "\n", PAGE_SIZE);
+
+	mutex_unlock(&mutex);
+
+	return strlen(buffer);
+}
+
+static ssize_t parent_store(struct device *dev,
+	struct device_attribute *attr, const char *buffer, size_t count)
+{
+	struct clk *parent;
+
+	char *s = kstrdup(buffer, GFP_KERNEL);
+
+	if (!s)
+		return -ENOMEM;
+	if (s[strlen(s) - 1] == '\n')
+		s[strlen(s) - 1] = '\0';
+	parent = clk_get(dev, s);
+	kfree(s);
+	if (IS_ERR(parent))
+		return PTR_ERR(parent);
+
+	mutex_lock(&mutex);
+
+	clk_set_parent(dev_get_drvdata(dev), parent);
+
+	mutex_unlock(&mutex);
+
+	clk_put(parent);
+	return count;
+}
+
+static DEVICE_ATTR(rate, S_IRUGO | S_IWUSR, rate_show, rate_store);
+static DEVICE_ATTR(parent, S_IRUGO | S_IWUSR, parent_show, parent_store);
+
+static const struct attribute *clock_attrs[] = {
+	&dev_attr_rate.attr,
+	&dev_attr_parent.attr,
+	NULL,
+};
+
+static const struct attribute_group clock_attr_group = {
+	.attrs = (struct attribute **) clock_attrs,
+};
+
+static struct class gpclock_class = {
+	.name =		"clock",
+	.owner =	THIS_MODULE,
+};
+
+static int create_clock_attr(struct clk *clk, void *data)
+{
+	struct device *dev;
+	const char *name;
+
+	name = clk_get_name(clk);
+	if (name == NULL || IS_ERR(name)) {
+		pr_debug("Invalid clock's name\n");
+		return PTR_ERR(name);
+	}
+	dev = device_create(&gpclock_class, (struct device *)data, MKDEV(0, 0),
+		clk, name);
+	if (!dev)
+		return -ENODEV;
+	return sysfs_create_group(&dev->kobj, &clock_attr_group);
+}
+
+static int __init gpclock_init(void)
+{
+	int ret;
+
+	ret = class_register(&gpclock_class);
+	if (ret >= 0)
+		ret = clk_for_each(create_clock_attr, NULL);
+	return ret;
+}
+subsys_initcall(gpclock_init);
+
diff -urpN linux-2.6.29-rc2/Documentation/ABI/testing/sysfs-class-clock
linux-2.6.29-rc2.elpa/Documentation/ABI/testing/sysfs-class-clock
--- linux-2.6.29-rc2/Documentation/ABI/testing/sysfs-class-clock	1970-01-01
01:00:00.000000000 +0100
+++ linux-2.6.29-rc2.elpa/Documentation/ABI/testing/sysfs-class-clock	2009-01-28
19:21:43.000000000 +0100
@@ -0,0 +1,20 @@
+What:		/sys/class/clock
+Date:		January 2009
+Contact:	Davide Rizzo <elpa.rizzo@gmail.com>
+Description:
+		The /sys/class/clock directory will consist of a group of
+		subdirectories each one describing an internal clock in the kernel.
+		The name of the subdirectory is the clock's name.
+		If a clock is device specific, its name is in the form "name.id".
+		In each directory there are 2 virtual files: rate and parent.
+		Both these files are r/w, but there can be some architecture-dependent
+		limitations on write access on one or both of them.
+		For this interface to work, it needs some low-level implementations (look
+		at include/linux/clk.h):
+		- clk_for_each()
+		- clk_name()
+		- clk_get() should recognize also the "name.id" format
+		Actually I implemented these only for Samsung S3C SoC in
+		arch/arm/plat-s3c/clock.c
+
+Users:

[PATCH 2/2] Driver for user access to internal clocks

[Davide Rizzo]

This is a proposal for adding 2 functions to clk interface to allow higher
 level drivers to enumerate and list all clocks, and to modify clk_get
 to accept device specific clk names in the form "name.id"
There is also the implementation for Samsung S3C24xx platform.

Signed-off-by: Davide Rizzo <elpa.rizzo@gmail.com>
---diff -urpN linux-2.6.29-rc2/arch/arm/plat-s3c/clock.c
linux-2.6.29-rc2.elpa/arch/arm/plat-s3c/clock.c
--- linux-2.6.29-rc2/arch/arm/plat-s3c/clock.c  2009-01-17
11:32:38.000000000 +0100
+++ linux-2.6.29-rc2.elpa/arch/arm/plat-s3c/clock.c     2009-01-28
19:32:08.000000000 +0100
@@ -69,11 +69,19 @@ static int clk_null_enable(struct clk *c

 struct clk *clk_get(struct device *dev, const char *id)
 {
+       long idno;
+       char *name = (char *)id;
+       char *dotpos = strrchr(id, '.');
       struct clk *p;
       struct clk *clk = ERR_PTR(-ENOENT);
-       int idno;

-       if (dev == NULL || dev->bus != &platform_bus_type)
+       if (dotpos) {
+               int err = strict_strtol(dotpos + 1, 10, &idno);
+               if (err)
+                               return ERR_PTR(err);
+               name = kstrdup(id, GFP_KERNEL);
+               name[dotpos - id] = '\0';
+       } else if (dev == NULL || dev->bus != &platform_bus_type)
               idno = -1;
       else
               idno = to_platform_device(dev)->id;
@@ -82,7 +90,7 @@ struct clk *clk_get(struct device *dev,

       list_for_each_entry(p, &clocks, list) {
               if (p->id == idno &&
-                   strcmp(id, p->name) == 0 &&
+                   strcmp(name, p->name) == 0 &&
                   try_module_get(p->owner)) {
                       clk = p;
                       break;
@@ -94,7 +102,7 @@ struct clk *clk_get(struct device *dev,

       if (IS_ERR(clk)) {
               list_for_each_entry(p, &clocks, list) {
-                       if (p->id == -1 && strcmp(id, p->name) == 0 &&
+                       if (p->id == -1 && strcmp(name, p->name) == 0 &&
                           try_module_get(p->owner)) {
                               clk = p;
                               break;
@@ -103,6 +111,8 @@ struct clk *clk_get(struct device *dev,
       }

       spin_unlock(&clocks_lock);
+       if (dotpos)
+               kfree(name);
       return clk;
 }

@@ -222,6 +232,42 @@ EXPORT_SYMBOL(clk_set_rate);
 EXPORT_SYMBOL(clk_get_parent);
 EXPORT_SYMBOL(clk_set_parent);

+int clk_for_each(int(*fn)(struct clk *, void *), void *data)
+       {
+       struct clk *clk;
+       int ret = 0;
+
+       list_for_each_entry(clk, &clocks, list)
+       {
+               ret = fn(clk, data);
+               if (ret)
+                       break;
+       }
+       return ret;
+}
+EXPORT_SYMBOL(clk_for_each);
+
+/* Returned pointer must be deallocated with kfree() */
+const char *clk_get_name(struct clk *clk)
+{
+       char *s;
+       int len;
+
+       if (IS_ERR(clk))
+               return ERR_PTR(-EINVAL);
+
+       len = strlen(clk->name) + 8;
+       s = kmalloc(len, GFP_KERNEL);
+       if (!s)
+               return ERR_PTR(-ENOMEM);
+       if (clk->id == -1)
+               strlcpy(s, clk->name, len);
+       else if (snprintf(s, len, "%s.%d", clk->name, clk->id) > len)
+               s[len - 1] = '\0';
+       return s;
+}
+EXPORT_SYMBOL(clk_get_name);
+
 /* base clocks */

 static int clk_default_setrate(struct clk *clk, unsigned long rate)
diff -urpN linux-2.6.29-rc2/include/linux/clk.h
linux-2.6.29-rc2.elpa/include/linux/clk.h
--- linux-2.6.29-rc2/include/linux/clk.h        2008-12-25
00:26:37.000000000 +0100
+++ linux-2.6.29-rc2.elpa/include/linux/clk.h   2009-01-28
19:21:43.000000000 +0100
@@ -125,4 +125,22 @@ int clk_set_parent(struct clk *clk, stru
 */
 struct clk *clk_get_parent(struct clk *clk);

+/**
+ * clk_for_each - calls fn, iterating between registered clocks
+ * @fn: function to be called, passing each clk structure in 1st argument
+ * @data: 2nd argument to pass to fn function
+ *
+ * Returns 0 or the called fn return code if != 0
+ */
+int clk_for_each(int(*fn)(struct clk *, void *), void *data);
+
+/**
+ * clk_name - get clock name
+ * @clk: clock source
+ *
+ * Returns clock's name that must be deallocated with kfree(), or valid
+ * IS_ERR() condition containing errno.
+ */
+const char *clk_get_name(struct clk *clk);
+
 #endif