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linux/drivers/watchdog/ar7_wdt.c
Arnd Bergmann 6038f373a3 llseek: automatically add .llseek fop 
All file_operations should get a .llseek operation so we can make
nonseekable_open the default for future file operations without a
.llseek pointer.

The three cases that we can automatically detect are no_llseek, seq_lseek
and default_llseek. For cases where we can we can automatically prove that
the file offset is always ignored, we use noop_llseek, which maintains
the current behavior of not returning an error from a seek.

New drivers should normally not use noop_llseek but instead use no_llseek
and call nonseekable_open at open time.  Existing drivers can be converted
to do the same when the maintainer knows for certain that no user code
relies on calling seek on the device file.

The generated code is often incorrectly indented and right now contains
comments that clarify for each added line why a specific variant was
chosen. In the version that gets submitted upstream, the comments will
be gone and I will manually fix the indentation, because there does not
seem to be a way to do that using coccinelle.

Some amount of new code is currently sitting in linux-next that should get
the same modifications, which I will do at the end of the merge window.

Many thanks to Julia Lawall for helping me learn to write a semantic
patch that does all this.

===== begin semantic patch =====
// This adds an llseek= method to all file operations,
// as a preparation for making no_llseek the default.
//
// The rules are
// - use no_llseek explicitly if we do nonseekable_open
// - use seq_lseek for sequential files
// - use default_llseek if we know we access f_pos
// - use noop_llseek if we know we don't access f_pos,
//   but we still want to allow users to call lseek
//
@ open1 exists @
identifier nested_open;
@@
nested_open(...)
{
<+...
nonseekable_open(...)
...+>
}

@ open exists@
identifier open_f;
identifier i, f;
identifier open1.nested_open;
@@
int open_f(struct inode *i, struct file *f)
{
<+...
(
nonseekable_open(...)
|
nested_open(...)
)
...+>
}

@ read disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
<+...
(
   *off = E
|
   *off += E
|
   func(..., off, ...)
|
   E = *off
)
...+>
}

@ read_no_fpos disable optional_qualifier exists @
identifier read_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off)
{
... when != off
}

@ write @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
expression E;
identifier func;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
<+...
(
  *off = E
|
  *off += E
|
  func(..., off, ...)
|
  E = *off
)
...+>
}

@ write_no_fpos @
identifier write_f;
identifier f, p, s, off;
type ssize_t, size_t, loff_t;
@@
ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off)
{
... when != off
}

@ fops0 @
identifier fops;
@@
struct file_operations fops = {
 ...
};

@ has_llseek depends on fops0 @
identifier fops0.fops;
identifier llseek_f;
@@
struct file_operations fops = {
...
 .llseek = llseek_f,
...
};

@ has_read depends on fops0 @
identifier fops0.fops;
identifier read_f;
@@
struct file_operations fops = {
...
 .read = read_f,
...
};

@ has_write depends on fops0 @
identifier fops0.fops;
identifier write_f;
@@
struct file_operations fops = {
...
 .write = write_f,
...
};

@ has_open depends on fops0 @
identifier fops0.fops;
identifier open_f;
@@
struct file_operations fops = {
...
 .open = open_f,
...
};

// use no_llseek if we call nonseekable_open
////////////////////////////////////////////
@ nonseekable1 depends on !has_llseek && has_open @
identifier fops0.fops;
identifier nso ~= "nonseekable_open";
@@
struct file_operations fops = {
...  .open = nso, ...
+.llseek = no_llseek, /* nonseekable */
};

@ nonseekable2 depends on !has_llseek @
identifier fops0.fops;
identifier open.open_f;
@@
struct file_operations fops = {
...  .open = open_f, ...
+.llseek = no_llseek, /* open uses nonseekable */
};

// use seq_lseek for sequential files
/////////////////////////////////////
@ seq depends on !has_llseek @
identifier fops0.fops;
identifier sr ~= "seq_read";
@@
struct file_operations fops = {
...  .read = sr, ...
+.llseek = seq_lseek, /* we have seq_read */
};

// use default_llseek if there is a readdir
///////////////////////////////////////////
@ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier readdir_e;
@@
// any other fop is used that changes pos
struct file_operations fops = {
... .readdir = readdir_e, ...
+.llseek = default_llseek, /* readdir is present */
};

// use default_llseek if at least one of read/write touches f_pos
/////////////////////////////////////////////////////////////////
@ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read.read_f;
@@
// read fops use offset
struct file_operations fops = {
... .read = read_f, ...
+.llseek = default_llseek, /* read accesses f_pos */
};

@ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write.write_f;
@@
// write fops use offset
struct file_operations fops = {
... .write = write_f, ...
+	.llseek = default_llseek, /* write accesses f_pos */
};

// Use noop_llseek if neither read nor write accesses f_pos
///////////////////////////////////////////////////////////

@ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
identifier write_no_fpos.write_f;
@@
// write fops use offset
struct file_operations fops = {
...
 .write = write_f,
 .read = read_f,
...
+.llseek = noop_llseek, /* read and write both use no f_pos */
};

@ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier write_no_fpos.write_f;
@@
struct file_operations fops = {
... .write = write_f, ...
+.llseek = noop_llseek, /* write uses no f_pos */
};

@ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
identifier read_no_fpos.read_f;
@@
struct file_operations fops = {
... .read = read_f, ...
+.llseek = noop_llseek, /* read uses no f_pos */
};

@ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @
identifier fops0.fops;
@@
struct file_operations fops = {
...
+.llseek = noop_llseek, /* no read or write fn */
};
===== End semantic patch =====

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Julia Lawall <julia@diku.dk>
Cc: Christoph Hellwig <hch@infradead.org>
2010-10-15 15:53:27 +02:00

370 lines
8.8 KiB
C
Raw Blame History

/*
* drivers/watchdog/ar7_wdt.c
*
* Copyright (C) 2007 Nicolas Thill <nico@openwrt.org>
* Copyright (c) 2005 Enrik Berkhan <Enrik.Berkhan@akk.org>
*
* Some code taken from:
* National Semiconductor SCx200 Watchdog support
* Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/uaccess.h>
#include <linux/clk.h>
#include <asm/addrspace.h>
#include <asm/mach-ar7/ar7.h>
#define DRVNAME "ar7_wdt"
#define LONGNAME "TI AR7 Watchdog Timer"
MODULE_AUTHOR("Nicolas Thill <nico@openwrt.org>");
MODULE_DESCRIPTION(LONGNAME);
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
static int margin = 60;
module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds");
static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
#define READ_REG(x) readl((void __iomem *)&(x))
#define WRITE_REG(x, v) writel((v), (void __iomem *)&(x))
struct ar7_wdt {
u32 kick_lock;
u32 kick;
u32 change_lock;
u32 change;
u32 disable_lock;
u32 disable;
u32 prescale_lock;
u32 prescale;
};
static unsigned long wdt_is_open;
static spinlock_t wdt_lock;
static unsigned expect_close;
/* XXX currently fixed, allows max margin ~68.72 secs */
#define prescale_value 0xffff
/* Resource of the WDT registers */
static struct resource *ar7_regs_wdt;
/* Pointer to the remapped WDT IO space */
static struct ar7_wdt *ar7_wdt;
static struct clk *vbus_clk;
static void ar7_wdt_kick(u32 value)
{
WRITE_REG(ar7_wdt->kick_lock, 0x5555);
if ((READ_REG(ar7_wdt->kick_lock) & 3) == 1) {
WRITE_REG(ar7_wdt->kick_lock, 0xaaaa);
if ((READ_REG(ar7_wdt->kick_lock) & 3) == 3) {
WRITE_REG(ar7_wdt->kick, value);
return;
}
}
printk(KERN_ERR DRVNAME ": failed to unlock WDT kick reg\n");
}
static void ar7_wdt_prescale(u32 value)
{
WRITE_REG(ar7_wdt->prescale_lock, 0x5a5a);
if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 1) {
WRITE_REG(ar7_wdt->prescale_lock, 0xa5a5);
if ((READ_REG(ar7_wdt->prescale_lock) & 3) == 3) {
WRITE_REG(ar7_wdt->prescale, value);
return;
}
}
printk(KERN_ERR DRVNAME ": failed to unlock WDT prescale reg\n");
}
static void ar7_wdt_change(u32 value)
{
WRITE_REG(ar7_wdt->change_lock, 0x6666);
if ((READ_REG(ar7_wdt->change_lock) & 3) == 1) {
WRITE_REG(ar7_wdt->change_lock, 0xbbbb);
if ((READ_REG(ar7_wdt->change_lock) & 3) == 3) {
WRITE_REG(ar7_wdt->change, value);
return;
}
}
printk(KERN_ERR DRVNAME ": failed to unlock WDT change reg\n");
}
static void ar7_wdt_disable(u32 value)
{
WRITE_REG(ar7_wdt->disable_lock, 0x7777);
if ((READ_REG(ar7_wdt->disable_lock) & 3) == 1) {
WRITE_REG(ar7_wdt->disable_lock, 0xcccc);
if ((READ_REG(ar7_wdt->disable_lock) & 3) == 2) {
WRITE_REG(ar7_wdt->disable_lock, 0xdddd);
if ((READ_REG(ar7_wdt->disable_lock) & 3) == 3) {
WRITE_REG(ar7_wdt->disable, value);
return;
}
}
}
printk(KERN_ERR DRVNAME ": failed to unlock WDT disable reg\n");
}
static void ar7_wdt_update_margin(int new_margin)
{
u32 change;
u32 vbus_rate;
vbus_rate = clk_get_rate(vbus_clk);
change = new_margin * (vbus_rate / prescale_value);
if (change < 1)
change = 1;
if (change > 0xffff)
change = 0xffff;
ar7_wdt_change(change);
margin = change * prescale_value / vbus_rate;
printk(KERN_INFO DRVNAME
": timer margin %d seconds (prescale %d, change %d, freq %d)\n",
margin, prescale_value, change, vbus_rate);
}
static void ar7_wdt_enable_wdt(void)
{
printk(KERN_DEBUG DRVNAME ": enabling watchdog timer\n");
ar7_wdt_disable(1);
ar7_wdt_kick(1);
}
static void ar7_wdt_disable_wdt(void)
{
printk(KERN_DEBUG DRVNAME ": disabling watchdog timer\n");
ar7_wdt_disable(0);
}
static int ar7_wdt_open(struct inode *inode, struct file *file)
{
/* only allow one at a time */
if (test_and_set_bit(0, &wdt_is_open))
return -EBUSY;
ar7_wdt_enable_wdt();
expect_close = 0;
return nonseekable_open(inode, file);
}
static int ar7_wdt_release(struct inode *inode, struct file *file)
{
if (!expect_close)
printk(KERN_WARNING DRVNAME
": watchdog device closed unexpectedly,"
"will not disable the watchdog timer\n");
else if (!nowayout)
ar7_wdt_disable_wdt();
clear_bit(0, &wdt_is_open);
return 0;
}
static ssize_t ar7_wdt_write(struct file *file, const char *data,
size_t len, loff_t *ppos)
{
/* check for a magic close character */
if (len) {
size_t i;
spin_lock(&wdt_lock);
ar7_wdt_kick(1);
spin_unlock(&wdt_lock);
expect_close = 0;
for (i = 0; i < len; ++i) {
char c;
if (get_user(c, data + i))
return -EFAULT;
if (c == 'V')
expect_close = 1;
}
}
return len;
}
static long ar7_wdt_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
static const struct watchdog_info ident = {
.identity = LONGNAME,
.firmware_version = 1,
.options = (WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
WDIOF_MAGICCLOSE),
};
int new_margin;
switch (cmd) {
case WDIOC_GETSUPPORT:
if (copy_to_user((struct watchdog_info *)arg, &ident,
sizeof(ident)))
return -EFAULT;
return 0;
case WDIOC_GETSTATUS:
case WDIOC_GETBOOTSTATUS:
if (put_user(0, (int *)arg))
return -EFAULT;
return 0;
case WDIOC_KEEPALIVE:
ar7_wdt_kick(1);
return 0;
case WDIOC_SETTIMEOUT:
if (get_user(new_margin, (int *)arg))
return -EFAULT;
if (new_margin < 1)
return -EINVAL;
spin_lock(&wdt_lock);
ar7_wdt_update_margin(new_margin);
ar7_wdt_kick(1);
spin_unlock(&wdt_lock);
case WDIOC_GETTIMEOUT:
if (put_user(margin, (int *)arg))
return -EFAULT;
return 0;
default:
return -ENOTTY;
}
}
static const struct file_operations ar7_wdt_fops = {
.owner = THIS_MODULE,
.write = ar7_wdt_write,
.unlocked_ioctl = ar7_wdt_ioctl,
.open = ar7_wdt_open,
.release = ar7_wdt_release,
.llseek = no_llseek,
};
static struct miscdevice ar7_wdt_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &ar7_wdt_fops,
};
static int __devinit ar7_wdt_probe(struct platform_device *pdev)
{
int rc;
spin_lock_init(&wdt_lock);
ar7_regs_wdt =
platform_get_resource_byname(pdev, IORESOURCE_MEM, "regs");
if (!ar7_regs_wdt) {
printk(KERN_ERR DRVNAME ": could not get registers resource\n");
rc = -ENODEV;
goto out;
}
if (!request_mem_region(ar7_regs_wdt->start,
resource_size(ar7_regs_wdt), LONGNAME)) {
printk(KERN_WARNING DRVNAME ": watchdog I/O region busy\n");
rc = -EBUSY;
goto out;
}
ar7_wdt = ioremap(ar7_regs_wdt->start, resource_size(ar7_regs_wdt));
if (!ar7_wdt) {
printk(KERN_ERR DRVNAME ": could not ioremap registers\n");
rc = -ENXIO;
goto out_mem_region;
}
vbus_clk = clk_get(NULL, "vbus");
if (IS_ERR(vbus_clk)) {
printk(KERN_ERR DRVNAME ": could not get vbus clock\n");
rc = PTR_ERR(vbus_clk);
goto out_mem_region;
}
ar7_wdt_disable_wdt();
ar7_wdt_prescale(prescale_value);
ar7_wdt_update_margin(margin);
rc = misc_register(&ar7_wdt_miscdev);
if (rc) {
printk(KERN_ERR DRVNAME ": unable to register misc device\n");
goto out_alloc;
}
goto out;
out_alloc:
iounmap(ar7_wdt);
out_mem_region:
release_mem_region(ar7_regs_wdt->start, resource_size(ar7_regs_wdt));
out:
return rc;
}
static int __devexit ar7_wdt_remove(struct platform_device *pdev)
{
misc_deregister(&ar7_wdt_miscdev);
iounmap(ar7_wdt);
release_mem_region(ar7_regs_wdt->start, resource_size(ar7_regs_wdt));
return 0;
}
static void ar7_wdt_shutdown(struct platform_device *pdev)
{
if (!nowayout)
ar7_wdt_disable_wdt();
}
static struct platform_driver ar7_wdt_driver = {
.probe = ar7_wdt_probe,
.remove = __devexit_p(ar7_wdt_remove),
.shutdown = ar7_wdt_shutdown,
.driver = {
.owner = THIS_MODULE,
.name = "ar7_wdt",
},
};
static int __init ar7_wdt_init(void)
{
return platform_driver_register(&ar7_wdt_driver);
}
static void __exit ar7_wdt_cleanup(void)
{
platform_driver_unregister(&ar7_wdt_driver);
}
module_init(ar7_wdt_init);
module_exit(ar7_wdt_cleanup);
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