X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=include%2Flinux%2Frtc.h;h=b01fe004cb5e5787ebc8e08ca514918a9b782fa6;hb=88bef5a4074e0568cf54df410f41065c06694d8a;hp=f2d0d15277216f9655ab254f3f9c9ef3ea471972;hpb=cc1bf182bb8451a036a7c227f0a95a0416c4736e;p=linux-2.6

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index f2d0d15277..b01fe004cb 100644
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -115,6 +115,23 @@ extern void rtc_time_to_tm(unsigned long time, struct rtc_time *tm);
 
 extern struct class *rtc_class;
 
+/*
+ * For these RTC methods the device parameter is the physical device
+ * on whatever bus holds the hardware (I2C, Platform, SPI, etc), which
+ * was passed to rtc_device_register().  Its driver_data normally holds
+ * device state, including the rtc_device pointer for the RTC.
+ *
+ * Most of these methods are called with rtc_device.ops_lock held,
+ * through the rtc_*(struct rtc_device *, ...) calls.
+ *
+ * The (current) exceptions are mostly filesystem hooks:
+ *   - the proc() hook for procfs
+ *   - non-ioctl() chardev hooks:  open(), release(), read_callback()
+ *   - periodic irq calls:  irq_set_state(), irq_set_freq()
+ *
+ * REVISIT those periodic irq calls *do* have ops_lock when they're
+ * issued through ioctl() ...
+ */
 struct rtc_class_ops {
 	int (*open)(struct device *);
 	void (*release)(struct device *);