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Message-ID: <b83f47cd-2b4f-4681-8f3e-d6123cbf48ce@roeck-us.net>
Date: Wed, 5 Jun 2024 07:04:51 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: linux-hwmon@...r.kernel.org, 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>, Armin Wolf <W_Armin@....de>,
Stephen Horvath <s.horvath@...look.com.au>
Subject: Re: [PATCH v4a 6/6] hwmon: (spd5118) Add configuration option for
auto-detection
On 6/5/24 02:22, Thomas Weißschuh wrote:
> On 2024-06-04 19:19:07+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@...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,
>> };
>
> For the if-deffery I proposed something during the last review,
> I'm not sure if you saw it. If you did, please ignore this comment:
>
I missed that, sorry (and I hope I didn't miss anything else).
>
> .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.
It does let me drop the #ifdef, so I agree it is a bit better.
I made that change, but I'll wait for a couple of days before sending
the updated version to give others time for additional feedback.
Thanks,
Guenter
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