tiny patch for RTC async I/O in 2.3.41

[Paul Barton-Davis]

I submitted this to Paul Gortmaker last year, and heard nothing. I
sent it to Alan, and heard nothing. So here is a new patch, fresh
against 2.3.41, to add async I/O (SIGIO) support to the RTC driver. It
would be nice for this to be in 2.4 - its a very useful complement to
the improvements for low latency in this kernel.

Sorry if the patch file order is wrong.

--p

--- linux/drivers/char/rtc.c.orig	Tue Jan 25 17:13:47 2000
+++ linux/drivers/char/rtc.c	Mon Jan 31 00:10:14 2000
@@ -34,10 +34,10 @@
  *	1.09	Nikita Schmidt: epoch support and some Alpha cleanup.
  *	1.09a	Pete Zaitcev: Sun SPARC
  *	1.09b	Jeff Garzik: Modularize, init cleanup
- *
+ *	1.10    Paul Barton-Davis: add support for async I/O
  */
 
-#define RTC_VERSION		"1.09b"
+#define RTC_VERSION		"1.10"
 
 #define RTC_IRQ 	8	/* Can't see this changing soon.	*/
 #define RTC_IO_EXTENT	0x10	/* Only really two ports, but...	*/
@@ -50,6 +50,7 @@
  *	this driver.)
  */
 
+#include <linux/version.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/types.h>
@@ -80,6 +81,8 @@
  *	ioctls.
  */
 
+static struct fasync_struct *rtc_async_queue;
+
 static DECLARE_WAIT_QUEUE_HEAD(rtc_wait);
 
 static spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
@@ -153,6 +156,13 @@
 
 	wake_up_interruptible(&rtc_wait);	
 
+	if (rtc_async_queue)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,3,0) 
+		kill_fasync (rtc_async_queue, SIGIO);
+#else
+		kill_fasync (rtc_async_queue, SIGIO, POLL_IN);
+#endif
+
 	if (atomic_read(&rtc_status) & RTC_TIMER_ON)
 		mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
 }
@@ -480,6 +490,12 @@
 	return 0;
 }
 
+static int rtc_fasync (int fd, struct file *filp, int on)
+
+{
+	return fasync_helper (fd, filp, on, &rtc_async_queue);
+}
+
 static int rtc_release(struct inode *inode, struct file *file)
 {
 	/*
@@ -504,6 +520,10 @@
 		del_timer(&rtc_irq_timer);
 	}
 
+	if (file->f_flags & FASYNC) {
+		rtc_fasync (-1, file, 0);
+	}
+
 	MOD_DEC_USE_COUNT;
 
 	spin_lock_irqsave (&rtc_lock, flags);
@@ -542,7 +562,9 @@
 	NULL,		/* No mmap */
 	rtc_open,
 	NULL,		/* flush */
-	rtc_release
+	rtc_release,
+	NULL,           /* fsync */
+	rtc_fasync
 };
 
 static struct miscdevice rtc_dev=

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