clocksource: add read2() callback

PATCH In review Magnus Damm 2 participants 2 messages Dec 1, 2008

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SuperH Timekeeping, clocksource core, NTP, alarmtimer

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Magnus Damm

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2008-12-01 10:33 UTC #0 lore raw

PATCH 8/10 clocksource: add read2() callback

From: Magnus Damm <[email protected]>

Add a read2() callback for clocksources. This callback is passing a pointer to struct clocksource which makes it easy to share the same callback for multiple clocksource instances.

The function clocksource_read() is modified to prefer read2() over read() if initialized.

Signed-off-by Magnus Damm <[email protected]>

---

 include/linux/clocksource.h |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

include/linux/clocksource.h +3 -1

@@ -43,6 +43,7 @@ struct clocksource;
  *				The ideal clocksource. A must-use where
  *				available.
  * @read:		returns a cycle value
+ * @read2:		returns a cycle value, passes clocksource as argument
  * @mask:		bitmask for two's complement
  *			subtraction of non 64 bit counters
  * @mult:		cycle to nanosecond multiplier (adjusted by NTP)

@@ -62,6 +63,7 @@ struct clocksource {
 	struct list_head list;
 	int rating;
 	cycle_t (*read)(void);
+	cycle_t (*read2)(struct clocksource *cs);
 	cycle_t mask;
 	u32 mult;
 	u32 mult_orig;

@@ -170,7 +172,7 @@ static inline u32 clocksource_hz2mult(u3
  */
 static inline cycle_t clocksource_read(struct clocksource *cs)
 {
-	return cs->read();
+	return cs->read2 ? cs->read2(cs) : cs->read();
 }
 
 /**

john stultz

2008-12-01 20:57 UTC #1 lore raw

Quoted 10 lines · Magnus Damm

From: Magnus Damm <[email protected]>
Add a read2() callback for clocksources. This callback is passing a pointer to struct clocksource which makes it easy to share the same callback for multiple clocksource instances.
The function clocksource_read() is modified to prefer read2() over read() if initialized.
Signed-off-by Magnus Damm <[email protected]>

I'm still not yet totally sold on the reasons we need this change, but I don't have any issue with this implementation. Hopefully the discussion around the timer_inc code will help resolve my concerns.

Also, if we're going to go this way, you might want to add read() to the feature-removal list and add a warning in clocksource_register() for any clocksource that doesn't implement read2, just so we don't have to keep both around forever

thanks
-john

Quoted 32 lines

---

 include/linux/clocksource.h |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

include/linux/clocksource.h +3 -1

@@ -43,6 +43,7 @@ struct clocksource;
  *				The ideal clocksource. A must-use where
  *				available.
  * @read:		returns a cycle value
+ * @read2:		returns a cycle value, passes clocksource as argument
  * @mask:		bitmask for two's complement
  *			subtraction of non 64 bit counters
  * @mult:		cycle to nanosecond multiplier (adjusted by NTP)

@@ -62,6 +63,7 @@ struct clocksource {
 	struct list_head list;
 	int rating;
 	cycle_t (*read)(void);
+	cycle_t (*read2)(struct clocksource *cs);
 	cycle_t mask;
 	u32 mult;
 	u32 mult_orig;

@@ -170,7 +172,7 @@ static inline u32 clocksource_hz2mult(u3
  */
 static inline cycle_t clocksource_read(struct clocksource *cs)
 {
-	return cs->read();
+	return cs->read2 ? cs->read2(cs) : cs->read();
 }
 
 /**