Date:	Thu, 8 Jan 2009 17:06:58 +0100
From:	"Davide Rizzo" <elpa.rizzo@...il.com>
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, gregkh@...e.de, ben-linux@...ff.org
Subject: Re: [PATCH 1/3] Driver for user access to internal clocks

> 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@...il.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@...il.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@...il.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
--
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