linux-kernel - [PATCH 2/8] counter: ftm-quaddec: Use container_of instead of struct counter

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Date:   Tue, 21 Dec 2021 11:45:40 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Patrick Havelange <patrick.havelange@...ensium.com>,
        William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/8] counter: ftm-quaddec: Use container_of instead of struct counter_device::priv

Using counter->priv is a memory read and so more expensive than
container_of which is only an addition. (In this case even a noop
because the offset is 0.)

So container_of is expected to be a tad faster, it's type-safe, and
produces smaller code (ARCH=arm allmodconfig):

	add/remove: 0/0 grow/shrink: 0/5 up/down: 0/-60 (-60)
	Function                                     old     new   delta
	ftm_quaddec_set_prescaler                    612     600     -12
	ftm_quaddec_probe                            596     584     -12
	ftm_quaddec_get_prescaler                    156     144     -12
	ftm_quaddec_count_write                      232     220     -12
	ftm_quaddec_count_read                       152     140     -12
	Total: Before=5096, After=5036, chg -1.18%

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
 drivers/counter/ftm-quaddec.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/counter/ftm-quaddec.c b/drivers/counter/ftm-quaddec.c
index 5ef0478709cd..b58a4f54e97b 100644
--- a/drivers/counter/ftm-quaddec.c
+++ b/drivers/counter/ftm-quaddec.c
@@ -33,6 +33,11 @@ struct ftm_quaddec {
 	struct mutex ftm_quaddec_mutex;
 };
 
+static inline struct ftm_quaddec *ftm_from_counter(struct counter_device *counter)
+{
+	return container_of(counter, struct ftm_quaddec, counter);
+}
+
 static void ftm_read(struct ftm_quaddec *ftm, uint32_t offset, uint32_t *data)
 {
 	if (ftm->big_endian)
@@ -118,7 +123,7 @@ static void ftm_quaddec_disable(void *ftm)
 static int ftm_quaddec_get_prescaler(struct counter_device *counter,
 				     struct counter_count *count, u32 *cnt_mode)
 {
-	struct ftm_quaddec *ftm = counter->priv;
+	struct ftm_quaddec *ftm = ftm_from_counter(counter);
 	uint32_t scflags;
 
 	ftm_read(ftm, FTM_SC, &scflags);
@@ -131,7 +136,7 @@ static int ftm_quaddec_get_prescaler(struct counter_device *counter,
 static int ftm_quaddec_set_prescaler(struct counter_device *counter,
 				     struct counter_count *count, u32 cnt_mode)
 {
-	struct ftm_quaddec *ftm = counter->priv;
+	struct ftm_quaddec *ftm = ftm_from_counter(counter);
 
 	mutex_lock(&ftm->ftm_quaddec_mutex);
 
@@ -162,7 +167,7 @@ static int ftm_quaddec_count_read(struct counter_device *counter,
 				  struct counter_count *count,
 				  u64 *val)
 {
-	struct ftm_quaddec *const ftm = counter->priv;
+	struct ftm_quaddec *const ftm = ftm_from_counter(counter);
 	uint32_t cntval;
 
 	ftm_read(ftm, FTM_CNT, &cntval);
@@ -176,7 +181,7 @@ static int ftm_quaddec_count_write(struct counter_device *counter,
 				   struct counter_count *count,
 				   const u64 val)
 {
-	struct ftm_quaddec *const ftm = counter->priv;
+	struct ftm_quaddec *const ftm = ftm_from_counter(counter);
 
 	if (val != 0) {
 		dev_warn(&ftm->pdev->dev, "Can only accept '0' as new counter value\n");
@@ -292,7 +297,6 @@ static int ftm_quaddec_probe(struct platform_device *pdev)
 	ftm->counter.num_counts = 1;
 	ftm->counter.signals = ftm_quaddec_signals;
 	ftm->counter.num_signals = ARRAY_SIZE(ftm_quaddec_signals);
-	ftm->counter.priv = ftm;
 
 	mutex_init(&ftm->ftm_quaddec_mutex);
 
-- 
2.33.0