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

[Guenter Roeck]

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@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > 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