On 2024-06-03 21:02:37+0000, Guenter Roeck wrote:
> 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@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> 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.
The combination of
"In general it should only be enabled if necessary."
and
"default y" / "If unsure, say Y."
looks weird.
Also right now it is not possible to disable detection on non-DMI
configurations. But when using OF, custom kernel code or userspace
instantiation then neither DMI nor CONFIG_DETECT are necessary.
The following would support those usecases, too:
config SENSORS_SPD5118_DETECT
bool "Enable detect function"
depends on SENSORS_SPD5118
default !DMI
(And no "select SENSORS_SPD5118_DETECT if !DMI")
> +
> 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,
.address_list is also only needed with CONFIG_SENSORS_SPD5118_DETECT.
If you use
.detect = IS_ENABLED(CONFIG_SENSORS_SPD5118_DETECT) ? spd5118_detect : NULL,
.address_list = IS_ENABLED(CONFIG_SENSORS_SPD5118_DETECT) ? normal_i2c : NULL,
then the need for __maybe_unused goes away and type checking is a tiny
bit better.
