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linux/drivers/sbus/char/display7seg.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

291 lines
6.5 KiB
C
Raw Blame History

/* display7seg.c - Driver implementation for the 7-segment display
* present on Sun Microsystems CP1400 and CP1500
*
* Copyright (c) 2000 Eric Brower (ebrower@usa.net)
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/major.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h> /* request_region */
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <asm/atomic.h>
#include <asm/uaccess.h> /* put_/get_user */
#include <asm/io.h>
#include <asm/display7seg.h>
#define D7S_MINOR 193
#define DRIVER_NAME "d7s"
#define PFX DRIVER_NAME ": "
static DEFINE_MUTEX(d7s_mutex);
static int sol_compat = 0; /* Solaris compatibility mode */
/* Solaris compatibility flag -
* The Solaris implementation omits support for several
* documented driver features (ref Sun doc 806-0180-03).
* By default, this module supports the documented driver
* abilities, rather than the Solaris implementation:
*
* 1) Device ALWAYS reverts to OBP-specified FLIPPED mode
* upon closure of device or module unload.
* 2) Device ioctls D7SIOCRD/D7SIOCWR honor toggling of
* FLIP bit
*
* If you wish the device to operate as under Solaris,
* omitting above features, set this parameter to non-zero.
*/
module_param(sol_compat, int, 0);
MODULE_PARM_DESC(sol_compat,
"Disables documented functionality omitted from Solaris driver");
MODULE_AUTHOR("Eric Brower <ebrower@usa.net>");
MODULE_DESCRIPTION("7-Segment Display driver for Sun Microsystems CP1400/1500");
MODULE_LICENSE("GPL");
MODULE_SUPPORTED_DEVICE("d7s");
struct d7s {
void __iomem *regs;
bool flipped;
};
struct d7s *d7s_device;
/*
* Register block address- see header for details
* -----------------------------------------
* | DP | ALARM | FLIP | 4 | 3 | 2 | 1 | 0 |
* -----------------------------------------
*
* DP - Toggles decimal point on/off
* ALARM - Toggles "Alarm" LED green/red
* FLIP - Inverts display for upside-down mounted board
* bits 0-4 - 7-segment display contents
*/
static atomic_t d7s_users = ATOMIC_INIT(0);
static int d7s_open(struct inode *inode, struct file *f)
{
if (D7S_MINOR != iminor(inode))
return -ENODEV;
atomic_inc(&d7s_users);
return 0;
}
static int d7s_release(struct inode *inode, struct file *f)
{
/* Reset flipped state to OBP default only if
* no other users have the device open and we
* are not operating in solaris-compat mode
*/
if (atomic_dec_and_test(&d7s_users) && !sol_compat) {
struct d7s *p = d7s_device;
u8 regval = 0;
regval = readb(p->regs);
if (p->flipped)
regval |= D7S_FLIP;
else
regval &= ~D7S_FLIP;
writeb(regval, p->regs);
}
return 0;
}
static long d7s_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
struct d7s *p = d7s_device;
u8 regs = readb(p->regs);
int error = 0;
u8 ireg = 0;
if (D7S_MINOR != iminor(file->f_path.dentry->d_inode))
return -ENODEV;
mutex_lock(&d7s_mutex);
switch (cmd) {
case D7SIOCWR:
/* assign device register values we mask-out D7S_FLIP
* if in sol_compat mode
*/
if (get_user(ireg, (int __user *) arg)) {
error = -EFAULT;
break;
}
if (sol_compat) {
if (regs & D7S_FLIP)
ireg |= D7S_FLIP;
else
ireg &= ~D7S_FLIP;
}
writeb(ireg, p->regs);
break;
case D7SIOCRD:
/* retrieve device register values
* NOTE: Solaris implementation returns D7S_FLIP bit
* as toggled by user, even though it does not honor it.
* This driver will not misinform you about the state
* of your hardware while in sol_compat mode
*/
if (put_user(regs, (int __user *) arg)) {
error = -EFAULT;
break;
}
break;
case D7SIOCTM:
/* toggle device mode-- flip display orientation */
if (regs & D7S_FLIP)
regs &= ~D7S_FLIP;
else
regs |= D7S_FLIP;
writeb(regs, p->regs);
break;
};
mutex_unlock(&d7s_mutex);
return error;
}
static const struct file_operations d7s_fops = {
.owner = THIS_MODULE,
.unlocked_ioctl = d7s_ioctl,
.compat_ioctl = d7s_ioctl,
.open = d7s_open,
.release = d7s_release,
.llseek = noop_llseek,
};
static struct miscdevice d7s_miscdev = {
.minor = D7S_MINOR,
.name = DRIVER_NAME,
.fops = &d7s_fops
};
static int __devinit d7s_probe(struct platform_device *op,
const struct of_device_id *match)
{
struct device_node *opts;
int err = -EINVAL;
struct d7s *p;
u8 regs;
if (d7s_device)
goto out;
p = kzalloc(sizeof(*p), GFP_KERNEL);
err = -ENOMEM;
if (!p)
goto out;
p->regs = of_ioremap(&op->resource[0], 0, sizeof(u8), "d7s");
if (!p->regs) {
printk(KERN_ERR PFX "Cannot map chip registers\n");
goto out_free;
}
err = misc_register(&d7s_miscdev);
if (err) {
printk(KERN_ERR PFX "Unable to acquire miscdevice minor %i\n",
D7S_MINOR);
goto out_iounmap;
}
/* OBP option "d7s-flipped?" is honored as default for the
* device, and reset default when detached
*/
regs = readb(p->regs);
opts = of_find_node_by_path("/options");
if (opts &&
of_get_property(opts, "d7s-flipped?", NULL))
p->flipped = true;
if (p->flipped)
regs |= D7S_FLIP;
else
regs &= ~D7S_FLIP;
writeb(regs, p->regs);
printk(KERN_INFO PFX "7-Segment Display%s at [%s:0x%llx] %s\n",
op->dev.of_node->full_name,
(regs & D7S_FLIP) ? " (FLIPPED)" : "",
op->resource[0].start,
sol_compat ? "in sol_compat mode" : "");
dev_set_drvdata(&op->dev, p);
d7s_device = p;
err = 0;
out:
return err;
out_iounmap:
of_iounmap(&op->resource[0], p->regs, sizeof(u8));
out_free:
kfree(p);
goto out;
}
static int __devexit d7s_remove(struct platform_device *op)
{
struct d7s *p = dev_get_drvdata(&op->dev);
u8 regs = readb(p->regs);
/* Honor OBP d7s-flipped? unless operating in solaris-compat mode */
if (sol_compat) {
if (p->flipped)
regs |= D7S_FLIP;
else
regs &= ~D7S_FLIP;
writeb(regs, p->regs);
}
misc_deregister(&d7s_miscdev);
of_iounmap(&op->resource[0], p->regs, sizeof(u8));
kfree(p);
return 0;
}
static const struct of_device_id d7s_match[] = {
{
.name = "display7seg",
},
{},
};
MODULE_DEVICE_TABLE(of, d7s_match);
static struct of_platform_driver d7s_driver = {
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
.of_match_table = d7s_match,
},
.probe = d7s_probe,
.remove = __devexit_p(d7s_remove),
};
static int __init d7s_init(void)
{
return of_register_platform_driver(&d7s_driver);
}
static void __exit d7s_exit(void)
{
of_unregister_platform_driver(&d7s_driver);
}
module_init(d7s_init);
module_exit(d7s_exit);
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