[PATCH] RTC: rtc-dev UIE emulation

Import genrtc's RTC UIE emulation (CONFIG_GEN_RTC_X) to rtc-dev driver with
slight adjustments/refinements.  This makes UIE-less rtc drivers work
better with programs doing read/poll on /dev/rtc, such as hwclock.  This
emulation should not harm rtc drivers with UIE support, since
rtc_dev_ioctl() calls underlaying rtc driver's ioctl() first.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 109 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 9e249650baf0..725d6b696792 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -73,6 +73,13 @@ config RTC_INTF_DEV
           This driver can also be built as a module. If so, the module
           will be called rtc-dev.
 
+config RTC_INTF_DEV_UIE_EMUL
+        bool "RTC UIE emulation on dev interface"
+        depends on RTC_INTF_DEV
+        help
+          Provides an emulation for RTC_UIE if the underlaying rtc chip
+          driver did not provide RTC_UIE ioctls.
+
 comment "RTC drivers"
         depends on RTC_CLASS
 
diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 2011567005f9..07387c99df0d 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -48,6 +48,93 @@ static int rtc_dev_open(struct inode *inode, struct file *file)
         return err;
 }
 
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+/*
+ * Routine to poll RTC seconds field for change as often as possible,
+ * after first RTC_UIE use timer to reduce polling
+ */
+static void rtc_uie_task(void *data)
+{
+        struct rtc_device *rtc = data;
+        struct rtc_time tm;
+        int num = 0;
+        int err;
+
+        err = rtc_read_time(&rtc->class_dev, &tm);
+        spin_lock_irq(&rtc->irq_lock);
+        if (rtc->stop_uie_polling || err) {
+                rtc->uie_task_active = 0;
+        } else if (rtc->oldsecs != tm.tm_sec) {
+                num = (tm.tm_sec + 60 - rtc->oldsecs) % 60;
+                rtc->oldsecs = tm.tm_sec;
+                rtc->uie_timer.expires = jiffies + HZ - (HZ/10);
+                rtc->uie_timer_active = 1;
+                rtc->uie_task_active = 0;
+                add_timer(&rtc->uie_timer);
+        } else if (schedule_work(&rtc->uie_task) == 0) {
+                rtc->uie_task_active = 0;
+        }
+        spin_unlock_irq(&rtc->irq_lock);
+        if (num)
+                rtc_update_irq(&rtc->class_dev, num, RTC_UF | RTC_IRQF);
+}
+
+static void rtc_uie_timer(unsigned long data)
+{
+        struct rtc_device *rtc = (struct rtc_device *)data;
+        unsigned long flags;
+
+        spin_lock_irqsave(&rtc->irq_lock, flags);
+        rtc->uie_timer_active = 0;
+        rtc->uie_task_active = 1;
+        if ((schedule_work(&rtc->uie_task) == 0))
+                rtc->uie_task_active = 0;
+        spin_unlock_irqrestore(&rtc->irq_lock, flags);
+}
+
+static void clear_uie(struct rtc_device *rtc)
+{
+        spin_lock_irq(&rtc->irq_lock);
+        if (rtc->irq_active) {
+                rtc->stop_uie_polling = 1;
+                if (rtc->uie_timer_active) {
+                        spin_unlock_irq(&rtc->irq_lock);
+                        del_timer_sync(&rtc->uie_timer);
+                        spin_lock_irq(&rtc->irq_lock);
+                        rtc->uie_timer_active = 0;
+                }
+                if (rtc->uie_task_active) {
+                        spin_unlock_irq(&rtc->irq_lock);
+                        flush_scheduled_work();
+                        spin_lock_irq(&rtc->irq_lock);
+                }
+                rtc->irq_active = 0;
+        }
+        spin_unlock_irq(&rtc->irq_lock);
+}
+
+static int set_uie(struct rtc_device *rtc)
+{
+        struct rtc_time tm;
+        int err;
+
+        err = rtc_read_time(&rtc->class_dev, &tm);
+        if (err)
+                return err;
+        spin_lock_irq(&rtc->irq_lock);
+        if (!rtc->irq_active) {
+                rtc->irq_active = 1;
+                rtc->stop_uie_polling = 0;
+                rtc->oldsecs = tm.tm_sec;
+                rtc->uie_task_active = 1;
+                if (schedule_work(&rtc->uie_task) == 0)
+                        rtc->uie_task_active = 0;
+        }
+        rtc->irq_data = 0;
+        spin_unlock_irq(&rtc->irq_lock);
+        return 0;
+}
+#endif /* CONFIG_RTC_INTF_DEV_UIE_EMUL */
 
 static ssize_t
 rtc_dev_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
@@ -232,6 +319,14 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file,
                         return -EFAULT;
                 break;
 
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+        case RTC_UIE_OFF:
+                clear_uie(rtc);
+                return 0;
+
+        case RTC_UIE_ON:
+                return set_uie(rtc);
+#endif
         default:
                 err = -ENOTTY;
                 break;
@@ -244,6 +339,9 @@ static int rtc_dev_release(struct inode *inode, struct file *file)
 {
         struct rtc_device *rtc = to_rtc_device(file->private_data);
 
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+        clear_uie(rtc);
+#endif
         if (rtc->ops->release)
                 rtc->ops->release(rtc->class_dev.dev);
 
@@ -284,6 +382,10 @@ static int rtc_dev_add_device(struct class_device *class_dev,
         mutex_init(&rtc->char_lock);
         spin_lock_init(&rtc->irq_lock);
         init_waitqueue_head(&rtc->irq_queue);
+#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
+        INIT_WORK(&rtc->uie_task, rtc_uie_task, rtc);
+        setup_timer(&rtc->uie_timer, rtc_uie_timer, (unsigned long)rtc);
+#endif
 
         cdev_init(&rtc->char_dev, &rtc_dev_fops);
         rtc->char_dev.owner = rtc->owner;