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Sender: Guenter Roeck <groeck7@gmail.com>
From: Guenter Roeck <linux@roeck-us.net>
To: linux-hwmon@vger.kernel.org
Cc: Rob Herring <robh@kernel.org>,
	linux-kernel@vger.kernel.org,
	Peter Yin <peteryin.openbmc@gmail.com>,
	Potin Lai <potin.lai.pt@gmail.com>,
	Daniel Matyas <daniel.matyas@analog.com>,
	Andrew Davis <afd@ti.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	Guenter Roeck <linux@roeck-us.net>
Subject: [PATCH 4/4] hwmon: (pmbus/max31827) Explain why enum chips must not start with 0
Date: Mon, 10 Jun 2024 11:10:46 -0700
Message-Id: <20240610181046.1991436-5-linux@roeck-us.net>
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If a driver calls device_get_match_data(), the .data pointer in its id
data structures must not be NULL/0 because device_get_match_data()
returns NULL if an entry is not found. Explain that in a comment to avoid
confusion why this is required in this driver but not in other drivers.

Cc: Daniel Matyas <daniel.matyas@analog.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/max31827.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/hwmon/max31827.c b/drivers/hwmon/max31827.c
index f8a13b30f100..391cb059e94d 100644
--- a/drivers/hwmon/max31827.c
+++ b/drivers/hwmon/max31827.c
@@ -46,6 +46,11 @@
 #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
 #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)
 
+/*
+ * The enum passed in the .data pointer of struct of_device_id must
+ * start with a value != 0 since that is a requirement for using
+ * device_get_match_data().
+ */
 enum chips { max31827 = 1, max31828, max31829 };
 
 enum max31827_cnv {
-- 
2.39.2