linux/drivers/char/nwbutton.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

245 lines
7.9 KiB
C

/*
* NetWinder Button Driver-
* Copyright (C) Alex Holden <alex@linuxhacker.org> 1998, 1999.
*
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/timer.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/mach-types.h>
#define __NWBUTTON_C /* Tell the header file who we are */
#include "nwbutton.h"
static void button_sequence_finished (unsigned long parameters);
static int button_press_count; /* The count of button presses */
/* Times for the end of a sequence */
static DEFINE_TIMER(button_timer, button_sequence_finished, 0, 0);
static DECLARE_WAIT_QUEUE_HEAD(button_wait_queue); /* Used for blocking read */
static char button_output_buffer[32]; /* Stores data to write out of device */
static int bcount; /* The number of bytes in the buffer */
static int bdelay = BUTTON_DELAY; /* The delay, in jiffies */
static struct button_callback button_callback_list[32]; /* The callback list */
static int callback_count; /* The number of callbacks registered */
static int reboot_count = NUM_PRESSES_REBOOT; /* Number of presses to reboot */
/*
* This function is called by other drivers to register a callback function
* to be called when a particular number of button presses occurs.
* The callback list is a static array of 32 entries (I somehow doubt many
* people are ever going to want to register more than 32 different actions
* to be performed by the kernel on different numbers of button presses ;).
* However, if an attempt to register a 33rd entry (perhaps a stuck loop
* somewhere registering the same entry over and over?) it will fail to
* do so and return -ENOMEM. If an attempt is made to register a null pointer,
* it will fail to do so and return -EINVAL.
* Because callbacks can be unregistered at random the list can become
* fragmented, so we need to search through the list until we find the first
* free entry.
*
* FIXME: Has anyone spotted any locking functions int his code recently ??
*/
int button_add_callback (void (*callback) (void), int count)
{
int lp = 0;
if (callback_count == 32) {
return -ENOMEM;
}
if (!callback) {
return -EINVAL;
}
callback_count++;
for (; (button_callback_list [lp].callback); lp++);
button_callback_list [lp].callback = callback;
button_callback_list [lp].count = count;
return 0;
}
/*
* This function is called by other drivers to deregister a callback function.
* If you attempt to unregister a callback which does not exist, it will fail
* with -EINVAL. If there is more than one entry with the same address,
* because it searches the list from end to beginning, it will unregister the
* last one to be registered first (FILO- First In Last Out).
* Note that this is not neccessarily true if the entries are not submitted
* at the same time, because another driver could have unregistered a callback
* between the submissions creating a gap earlier in the list, which would
* be filled first at submission time.
*/
int button_del_callback (void (*callback) (void))
{
int lp = 31;
if (!callback) {
return -EINVAL;
}
while (lp >= 0) {
if ((button_callback_list [lp].callback) == callback) {
button_callback_list [lp].callback = NULL;
button_callback_list [lp].count = 0;
callback_count--;
return 0;
};
lp--;
};
return -EINVAL;
}
/*
* This function is called by button_sequence_finished to search through the
* list of callback functions, and call any of them whose count argument
* matches the current count of button presses. It starts at the beginning
* of the list and works up to the end. It will refuse to follow a null
* pointer (which should never happen anyway).
*/
static void button_consume_callbacks (int bpcount)
{
int lp = 0;
for (; lp <= 31; lp++) {
if ((button_callback_list [lp].count) == bpcount) {
if (button_callback_list [lp].callback) {
button_callback_list[lp].callback();
}
}
}
}
/*
* This function is called when the button_timer times out.
* ie. When you don't press the button for bdelay jiffies, this is taken to
* mean you have ended the sequence of key presses, and this function is
* called to wind things up (write the press_count out to /dev/button, call
* any matching registered function callbacks, initiate reboot, etc.).
*/
static void button_sequence_finished (unsigned long parameters)
{
#ifdef CONFIG_NWBUTTON_REBOOT /* Reboot using button is enabled */
if (button_press_count == reboot_count)
kill_cad_pid(SIGINT, 1); /* Ask init to reboot us */
#endif /* CONFIG_NWBUTTON_REBOOT */
button_consume_callbacks (button_press_count);
bcount = sprintf (button_output_buffer, "%d\n", button_press_count);
button_press_count = 0; /* Reset the button press counter */
wake_up_interruptible (&button_wait_queue);
}
/*
* This handler is called when the orange button is pressed (GPIO 10 of the
* SuperIO chip, which maps to logical IRQ 26). If the press_count is 0,
* this is the first press, so it starts a timer and increments the counter.
* If it is higher than 0, it deletes the old timer, starts a new one, and
* increments the counter.
*/
static irqreturn_t button_handler (int irq, void *dev_id)
{
button_press_count++;
mod_timer(&button_timer, jiffies + bdelay);
return IRQ_HANDLED;
}
/*
* This function is called when a user space program attempts to read
* /dev/nwbutton. It puts the device to sleep on the wait queue until
* button_sequence_finished writes some data to the buffer and flushes
* the queue, at which point it writes the data out to the device and
* returns the number of characters it has written. This function is
* reentrant, so that many processes can be attempting to read from the
* device at any one time.
*/
static int button_read (struct file *filp, char __user *buffer,
size_t count, loff_t *ppos)
{
interruptible_sleep_on (&button_wait_queue);
return (copy_to_user (buffer, &button_output_buffer, bcount))
? -EFAULT : bcount;
}
/*
* This structure is the file operations structure, which specifies what
* callbacks functions the kernel should call when a user mode process
* attempts to perform these operations on the device.
*/
static const struct file_operations button_fops = {
.owner = THIS_MODULE,
.read = button_read,
.llseek = noop_llseek,
};
/*
* This structure is the misc device structure, which specifies the minor
* device number (158 in this case), the name of the device (for /proc/misc),
* and the address of the above file operations structure.
*/
static struct miscdevice button_misc_device = {
BUTTON_MINOR,
"nwbutton",
&button_fops,
};
/*
* This function is called to initialise the driver, either from misc.c at
* bootup if the driver is compiled into the kernel, or from init_module
* below at module insert time. It attempts to register the device node
* and the IRQ and fails with a warning message if either fails, though
* neither ever should because the device number and IRQ are unique to
* this driver.
*/
static int __init nwbutton_init(void)
{
if (!machine_is_netwinder())
return -ENODEV;
printk (KERN_INFO "NetWinder Button Driver Version %s (C) Alex Holden "
"<alex@linuxhacker.org> 1998.\n", VERSION);
if (misc_register (&button_misc_device)) {
printk (KERN_WARNING "nwbutton: Couldn't register device 10, "
"%d.\n", BUTTON_MINOR);
return -EBUSY;
}
if (request_irq (IRQ_NETWINDER_BUTTON, button_handler, IRQF_DISABLED,
"nwbutton", NULL)) {
printk (KERN_WARNING "nwbutton: IRQ %d is not free.\n",
IRQ_NETWINDER_BUTTON);
misc_deregister (&button_misc_device);
return -EIO;
}
return 0;
}
static void __exit nwbutton_exit (void)
{
free_irq (IRQ_NETWINDER_BUTTON, NULL);
misc_deregister (&button_misc_device);
}
MODULE_AUTHOR("Alex Holden");
MODULE_LICENSE("GPL");
module_init(nwbutton_init);
module_exit(nwbutton_exit);