linux-kernel - [PATCH v4 6/6] hwmon: (spd5118) Add configuration option for auto-detection

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Date: Mon,  3 Jun 2024 21:02:37 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: linux-hwmon@...r.kernel.org
Cc: linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	René Rebe <rene@...ctcode.de>,
	Thomas Weißschuh <linux@...ssschuh.net>,
	Armin Wolf <W_Armin@....de>,
	Stephen Horvath <s.horvath@...look.com.au>,
	Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH v4 6/6] hwmon: (spd5118) Add configuration option for auto-detection

With SPD5118 chip detection for the most part handled by the i2c-smbus
core using DMI information, the spd5118 driver no longer needs to
auto-detect spd5118 compliant chips.

Auto-detection by the driver is still needed on systems with no DMI support
or on systems with more than eight DIMMs and can not be removed entirely.
However, it affects boot time and introduces the risk of mis-identifying
chips. Add configuration option to be able to disable it on systems where
chip detection is handled outside the driver.

Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
v4: New patch

 drivers/hwmon/Kconfig   | 18 ++++++++++++++++++
 drivers/hwmon/spd5118.c |  4 +++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 7a84e7637b51..0bb1bdee3e43 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -2185,6 +2185,7 @@ config SENSORS_SPD5118
 	tristate "SPD5118 Compliant Temperature Sensors"
 	depends on I2C
 	select REGMAP_I2C
+	select SENSORS_SPD5118_DETECT if !DMI
 	help
 	  If you say yes here you get support for SPD5118 (JEDEC JESD300)
 	  compliant temperature sensors. Such sensors are found on DDR5 memory
@@ -2193,6 +2194,23 @@ config SENSORS_SPD5118
 	  This driver can also be built as a module. If so, the module
 	  will be called spd5118.
 
+config SENSORS_SPD5118_DETECT
+	bool "Enable detect function"
+	depends on SENSORS_SPD5118
+	default y
+	help
+	  If enabled, the driver auto-detects if a chip in the SPD address
+	  range is compliant to the SPD51888 standard and auto-instantiates
+	  if that is the case. If disabled, SPD5118 compliant devices have
+	  to be instantiated by other means. On systems with DMI support
+	  this will typically be done from DMI DDR detection code in the
+	  I2C SMBus subsystem.
+	  Disabling the detect function will speed up boot time and reduce
+	  the risk of mis-detecting SPD5118 compliant devices. In general
+	  it should only be enabled if necessary.
+
+	  If unsure, say Y.
+
 config SENSORS_TC74
 	tristate "Microchip TC74"
 	depends on I2C
diff --git a/drivers/hwmon/spd5118.c b/drivers/hwmon/spd5118.c
index 5cb5e52c0a38..19d203283a21 100644
--- a/drivers/hwmon/spd5118.c
+++ b/drivers/hwmon/spd5118.c
@@ -313,7 +313,7 @@ static bool spd5118_vendor_valid(u8 bank, u8 id)
 }
 
 /* Return 0 if detection is successful, -ENODEV otherwise */
-static int spd5118_detect(struct i2c_client *client, struct i2c_board_info *info)
+static int __maybe_unused spd5118_detect(struct i2c_client *client, struct i2c_board_info *info)
 {
 	struct i2c_adapter *adapter = client->adapter;
 	int regval;
@@ -647,7 +647,9 @@ static struct i2c_driver spd5118_driver = {
 	},
 	.probe		= spd5118_probe,
 	.id_table	= spd5118_id,
+#ifdef CONFIG_SENSORS_SPD5118_DETECT
 	.detect		= spd5118_detect,
+#endif
 	.address_list	= normal_i2c,
 };
 
-- 
2.39.2