[PATCH v4a 6/6] hwmon: (spd5118) Add configuration option for auto-detection

[Guenter Roeck <linux@roeck-us.net>]

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@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
Sent as v4a to avoid resending the entire series.

v4a:
    Do not auto-select SENSORS_SPD5118_DETECT if DMI is disabled
    Modify help text of SENSORS_SPD5118_DETECT
    Default SENSORS_SPD5118_DETECT to y if (!DMI || !X86)
     
v4: New patch

 drivers/hwmon/Kconfig   | 19 +++++++++++++++++++
 drivers/hwmon/spd5118.c |  4 +++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 7a84e7637b51..d5eced417fc3 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -2193,6 +2193,25 @@ 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 (!DMI || !X86)
+	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 X86 systems with DMI support
+	  this will typically be done from DMI DDR detection code in the
+	  I2C SMBus subsystem. Devicetree based systems will instantiate
+	  attached devices if the DIMMs are listed in the devicetree file.
+
+	  Disabling the detect function will speed up boot time and reduce
+	  the risk of mis-detecting SPD5118 compliant devices. However, it
+	  may result in missed DIMMs under some circumstances.
+
+	  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