[PATCH] Patch - sharing RTC timer between kernel and user space (2nd)

This patch to allow using of RTC timer inside the kernel space.  We can
use the RTC timer as timing source for ALSA sequencer. Patch by Takashi.

The patch adds these three functions and one structure to rtc.h and
rtc.c:

typedef struct rtc_task {
       void (*func)(void *private_data);
       void *private_data;
} rtc_task_t;

int rtc_register(rtc_task_t *task);
int rtc_unregister(rtc_task_t *task);
int rtc_control(rtc_task_t *t, unsigned int cmd, unsigned long arg);

					Jaroslav

drivers/char/Makefile

@@ -23,7 +23,7 @@ obj-y	 += mem.o tty_io.o n_tty.o tty_ioctl.o raw.o pty.o misc.o random.o
 
 export-objs     :=	busmouse.o console.o keyboard.o sysrq.o \
 			misc.o pty.o random.o selection.o serial.o \
-			sonypi.o tty_io.o tty_ioctl.o generic_serial.o
+			sonypi.o tty_io.o tty_ioctl.o generic_serial.o rtc.o
 
 mod-subdirs	:=	ftape drm pcmcia
 

drivers/char/rtc.c

@@ -41,9 +41,11 @@
  *	1.10c	Cesar Barros: SMP locking fixes and cleanup
  *	1.10d	Paul Gortmaker: delete paranoia check in rtc_exit
  *	1.10e	Maciej W. Rozycki: Handle DECstation's year weirdness.
+ *      1.11    Takashi Iwai: Kernel access functions
+ *			      rtc_register/rtc_unregister/rtc_control
  */
 
-#define RTC_VERSION		"1.10e"
+#define RTC_VERSION		"1.11"
 
 #define RTC_IO_EXTENT	0x10	/* Only really two ports, but...	*/
 
@@ -139,6 +141,11 @@ static unsigned long rtc_status = 0;	/* bitmapped status byte.	*/
 static unsigned long rtc_freq = 0;	/* Current periodic IRQ rate	*/
 static unsigned long rtc_irq_data = 0;	/* our output to the world	*/
 
+#if RTC_IRQ
+static spinlock_t rtc_task_lock = SPIN_LOCK_UNLOCKED;
+static rtc_task_t *rtc_callback = NULL;
+#endif
+
 /*
  *	If this driver ever becomes modularised, it will be really nice
  *	to make the epoch retain its value across module reload...
@@ -180,6 +187,10 @@ static void rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 	spin_unlock (&rtc_lock);
 
 	/* Now do the rest of the actions */
+	spin_lock(&rtc_task_lock);
+	if (rtc_callback)
+		rtc_callback->func(rtc_callback->private_data);
+	spin_unlock(&rtc_task_lock);
 	wake_up_interruptible(&rtc_wait);	
 
 	kill_fasync (&rtc_async_queue, SIGIO, POLL_IN);
@@ -244,8 +255,7 @@ static ssize_t rtc_read(struct file *file, char *buf,
 #endif
 }
 
-static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
-		     unsigned long arg)
+static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
 {
 	struct rtc_time wtime; 
 
@@ -295,7 +305,7 @@ static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 		 * We don't really want Joe User enabling more
 		 * than 64Hz of interrupts on a multi-user machine.
 		 */
-		if ((rtc_freq > 64) && (!capable(CAP_SYS_RESOURCE)))
+		if (!kernel && (rtc_freq > 64) && (!capable(CAP_SYS_RESOURCE)))
 			return -EACCES;
 
 		if (!(rtc_status & RTC_TIMER_ON)) {
@@ -493,7 +503,7 @@ static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 		 * We don't really want Joe User generating more
 		 * than 64Hz of interrupts on a multi-user machine.
 		 */
-		if ((arg > 64) && (!capable(CAP_SYS_RESOURCE)))
+		if (!kernel && (arg > 64) && (!capable(CAP_SYS_RESOURCE)))
 			return -EACCES;
 
 		while (arg > (1<<tmp))
@@ -539,6 +549,12 @@ static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 	return copy_to_user((void *)arg, &wtime, sizeof wtime) ? -EFAULT : 0;
 }
 
+static int rtc_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
+		     unsigned long arg)
+{
+	return rtc_do_ioctl(cmd, arg, 0);
+}
+
 /*
  *	We enforce only one user at a time here with the open/close.
  *	Also clear the previous interrupt data on an open, and clean
@@ -606,11 +622,8 @@ static int rtc_release(struct inode *inode, struct file *file)
 
 	spin_lock_irq (&rtc_lock);
 	rtc_irq_data = 0;
-	spin_unlock_irq (&rtc_lock);
-
-	/* No need for locking -- nobody else can do anything until this rmw is
-	 * committed, and no timer is running. */
 	rtc_status &= ~RTC_IS_OPEN;
+	spin_unlock_irq (&rtc_lock);
 	return 0;
 }
 
@@ -635,6 +648,88 @@ static unsigned int rtc_poll(struct file *file, poll_table *wait)
 }
 #endif
 
+/*
+ * exported stuffs
+ */
+
+EXPORT_SYMBOL(rtc_register);
+EXPORT_SYMBOL(rtc_unregister);
+EXPORT_SYMBOL(rtc_control);
+
+int rtc_register(rtc_task_t *task)
+{
+#if !RTC_IRQ
+	return -EIO;
+#else
+	if (task == NULL || task->func == NULL)
+		return -EINVAL;
+	spin_lock_irq(&rtc_lock);
+	if (rtc_status & RTC_IS_OPEN) {
+		spin_unlock_irq(&rtc_lock);
+		return -EBUSY;
+	}
+	spin_lock(&rtc_task_lock);
+	if (rtc_callback) {
+		spin_unlock(&rtc_task_lock);
+		spin_unlock_irq(&rtc_lock);
+		return -EBUSY;
+	}
+	rtc_status |= RTC_IS_OPEN;
+	rtc_callback = task;
+	spin_unlock(&rtc_task_lock);
+	spin_unlock_irq(&rtc_lock);
+	return 0;
+#endif
+}
+
+int rtc_unregister(rtc_task_t *task)
+{
+#if !RTC_IRQ
+	return -EIO;
+#else
+	unsigned char tmp;
+
+	spin_lock_irq(&rtc_task_lock);
+	if (rtc_callback != task) {
+		spin_unlock_irq(&rtc_task_lock);
+		return -ENXIO;
+	}
+	rtc_callback = NULL;
+	spin_lock(&rtc_lock);
+	/* disable controls */
+	tmp = CMOS_READ(RTC_CONTROL);
+	tmp &= ~RTC_PIE;
+	tmp &= ~RTC_AIE;
+	tmp &= ~RTC_UIE;
+	CMOS_WRITE(tmp, RTC_CONTROL);
+	CMOS_READ(RTC_INTR_FLAGS);
+	if (rtc_status & RTC_TIMER_ON) {
+		rtc_status &= ~RTC_TIMER_ON;
+		del_timer(&rtc_irq_timer);
+	}
+	rtc_status &= ~RTC_IS_OPEN;
+	spin_unlock(&rtc_lock);
+	spin_unlock_irq(&rtc_task_lock);
+	return 0;
+#endif
+}
+
+int rtc_control(rtc_task_t *task, unsigned int cmd, unsigned long arg)
+{
+#if !RTC_IRQ
+	return -EIO;
+#else
+	spin_lock_irq(&rtc_task_lock);
+	if (rtc_callback != task) {
+		spin_unlock_irq(&rtc_task_lock);
+		return -ENXIO;
+	}
+	spin_unlock_irq(&rtc_task_lock);
+	return rtc_do_ioctl(cmd, arg, 1);
+#endif
+}
+
+
 /*
  *	The various file operations we support.
  */
@@ -822,7 +917,6 @@ static void __exit rtc_exit (void)
 
 module_init(rtc_init);
 module_exit(rtc_exit);
-EXPORT_NO_SYMBOLS;
 
 #if RTC_IRQ
 /*

include/linux/rtc.h

@@ -66,4 +66,17 @@ struct rtc_wkalrm {
 #define RTC_WKALM_SET	_IOW('p', 0x0f, struct rtc_wkalrm)/* Set wakeup alarm*/
 #define RTC_WKALM_RD	_IOR('p', 0x10, struct rtc_wkalrm)/* Get wakeup alarm*/
 
+#ifdef __KERNEL__
+
+typedef struct rtc_task {
+	void (*func)(void *private_data);
+	void *private_data;
+} rtc_task_t;
+
+int rtc_register(rtc_task_t *task);
+int rtc_unregister(rtc_task_t *task);
+int rtc_control(rtc_task_t *t, unsigned int cmd, unsigned long arg);
+
+#endif /* __KERNEL__ */
+
 #endif /* _LINUX_RTC_H_ */