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Commit f4757af8 authored by Mariusz Gorski's avatar Mariusz Gorski Committed by Greg Kroah-Hartman
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staging: panel: Fix single-open policy race condition 



Fix the implementation of a single-open policy for both
devices (lcd and keypad) by using atomic_t instead of plain ints.

Signed-off-by: default avatarMariusz Gorski <marius.gorski@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 54fbb2da

drivers/staging/panel/panel.c

+10 −9
Original line number Diff line number Diff line
@@ -404,8 +404,11 @@ static unsigned char lcd_bits[LCD_PORTS][LCD_BITS][BIT_STATES]; 
#endif /* DEFAULT_PROFILE == 0 */



/* global variables */

static int keypad_open_cnt;	/* #times opened */

static int lcd_open_cnt;	/* #times opened */



/* Device single-open policy control */

static atomic_t lcd_available = ATOMIC_INIT(1);

static atomic_t keypad_available = ATOMIC_INIT(1);



static struct pardevice *pprt;



static int lcd_initialized;
@@ -1347,7 +1350,7 @@ static ssize_t lcd_write(struct file *file, 


static int lcd_open(struct inode *inode, struct file *file)

{

	if (lcd_open_cnt)

	if (!atomic_dec_and_test(&lcd_available))

		return -EBUSY;	/* open only once at a time */



	if (file->f_mode & FMODE_READ)	/* device is write-only */
@@ -1357,13 +1360,12 @@ static int lcd_open(struct inode *inode, struct file *file) 
		lcd_clear_display();

		lcd_must_clear = 0;

	}

	lcd_open_cnt++;

	return nonseekable_open(inode, file);

}



static int lcd_release(struct inode *inode, struct file *file)

{

	lcd_open_cnt--;

	atomic_inc(&lcd_available);

	return 0;

}
@@ -1627,20 +1629,19 @@ static ssize_t keypad_read(struct file *file, 


static int keypad_open(struct inode *inode, struct file *file)

{

	if (keypad_open_cnt)

	if (!atomic_dec_and_test(&keypad_available))

		return -EBUSY;	/* open only once at a time */



	if (file->f_mode & FMODE_WRITE)	/* device is read-only */

		return -EPERM;



	keypad_buflen = 0;	/* flush the buffer on opening */

	keypad_open_cnt++;

	return 0;

}



static int keypad_release(struct inode *inode, struct file *file)

{

	keypad_open_cnt--;

	atomic_inc(&keypad_available);

	return 0;

}
@@ -1663,7 +1664,7 @@ static void keypad_send_key(const char *string, int max_len) 
		return;



	/* send the key to the device only if a process is attached to it. */

	if (keypad_open_cnt > 0) {

	if (!atomic_read(&keypad_available)) {

		while (max_len-- && keypad_buflen < KEYPAD_BUFFER && *string) {

			keypad_buffer[(keypad_start + keypad_buflen++) %

				      KEYPAD_BUFFER] = *string++;