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

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Date: Fri, 7 Jun 2024 18:08:34 +0200
From: Armin Wolf <W_Armin@....de>
To: Guenter Roeck <linux@...ck-us.net>, 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>,
 Stephen Horvath <s.horvath@...look.com.au>
Subject: Re: [PATCH v4a 6/6] hwmon: (spd5118) Add configuration option for
 auto-detection

Am 05.06.24 um 04:19 schrieb Guenter Roeck:

> 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.

Tested-by: Armin Wolf <W_Armin@....de>

> Cc: Wolfram Sang <wsa+renesas@...g-engineering.com>
> Signed-off-by: Guenter Roeck <linux@...ck-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,
>   };
>