linux-kernel - [PATCH 1/2] iio: adc: at91_adc: use of_device_get_match

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Message-ID: <20200928125424.35921-1-alexandru.ardelean@analog.com>
Date:   Mon, 28 Sep 2020 15:54:23 +0300
From:   Alexandru Ardelean <alexandru.ardelean@...log.com>
To:     <linux-iio@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
CC:     <linux-kernel@...r.kernel.org>, <jic23@...nel.org>,
        <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <ludovic.desroches@...rochip.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>
Subject: [PATCH 1/2] iio: adc: at91_adc: use of_device_get_match_data() helper

This tries to solve a warning reported by the lkp bot:

>> drivers/iio/adc/at91_adc.c:1439:34: warning: unused variable
>> 'at91_adc_dt_ids' [-Wunused-const-variable]
   static const struct of_device_id at91_adc_dt_ids[] = {
                                    ^
   1 warning generated.

This shows up with 'compiler: clang version 12.0.0' and W=1 (as the bot
mentions).

Forward declarations for global variables can be a bit weird; forward
function declarations are more common.

Maybe another fix for this would have been to prefix with 'extern' the
'at91_adc_dt_ids' variable, thus making it more friendly as a forward
declaration. It would look weird, but it would work.

But, we can avoid that forward declaration altogether simply by obtaining
the private data with of_device_get_match_data().

This appeared after commit 4027860dcc4c ("iio: Kconfig: at91_adc: add
COMPILE_TEST dependency to driver"), which put this driver on the lkp's bot
radar.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
---
 drivers/iio/adc/at91_adc.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 9b2c548fae95..c9ec0a4a357e 100644
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -829,8 +829,6 @@ static u32 calc_startup_ticks_9x5(u32 startup_time, u32 adc_clk_khz)
 	return ticks;
 }
 
-static const struct of_device_id at91_adc_dt_ids[];
-
 static int at91_adc_probe_dt_ts(struct device_node *node,
 	struct at91_adc_state *st, struct device *dev)
 {
@@ -878,8 +876,7 @@ static int at91_adc_probe_dt(struct iio_dev *idev,
 	if (!node)
 		return -EINVAL;
 
-	st->caps = (struct at91_adc_caps *)
-		of_match_device(at91_adc_dt_ids, &pdev->dev)->data;
+	st->caps = (struct at91_adc_caps *)of_device_get_match_data(&pdev->dev);
 
 	st->use_external = of_property_read_bool(node, "atmel,adc-use-external-triggers");
 
-- 
2.17.1