linux-kernel - Re: [PATCH v2] hwmon: (tmp401) Add of_match

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Date:   Tue, 3 May 2022 07:35:15 +0200
From:   Camel Guo <camelg@...s.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Vincent Whitchurch <Vincent.Whitchurch@...s.com>
CC:     Camel Guo <Camel.Guo@...s.com>, Jean Delvare <jdelvare@...e.com>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        kernel <kernel@...s.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] hwmon: (tmp401) Add of_match_table

On 5/2/22 18:16, Guenter Roeck wrote:
> On 5/2/22 07:58, Vincent Whitchurch wrote:
>> On Mon, May 02, 2022 at 03:57:50PM +0200, Guenter Roeck wrote:
>>> On 5/2/22 02:19, Camel Guo wrote:
>>>> When tmp401 is built as kernel module, it won't be automatically loaded
>>>> even through there is a device node in the devicetree. e.g:
>>>>       i2c {
>>>>         #address-cells = <1>;
>>>>         #size-cells = <0>;
>>>>
>>>>         sensor@4c {
>>>>           compatible = "ti,tmp401";
>>>>           reg = <0x4c>;
>>>>         };
>>>>       };
>>>> In order to make sure it is loaded automatically, this commit adds
>>>> of_match_table for tmp401.
>>>>
>>>
>>> As mentioned before, historically i2c devices would instantiate based
>>> on the i2c match table. You are claiming that this is no longer the case.
>> 
>> Note that while the commit message in the first version of the patch did
>> wrongly claim that probe would not work without the of_match_table, this
>> corrected description in v2 does mention the actual problem: that the
>> module will not be automatically loaded without the of_match_table.  (If
>> the module is loaded manually or the driver is built-in to the kernel,
>> there is no problem.)
>> 
> 
> No, it doesn't. None of the information you provided below is mentioned
> in the description, but is essential to understand your patch and the
> reason for it.
> 
>> See commit 72fc64c68decf119466 ("hwmon: (tmp103) Add OF device ID
>> table") or commit 98b16a09861aa85d6 ("hwmon: (max31785) Add OF device ID
>> table") for similar changes to other hwmon drivers.
>> 
> 
> Those commits provide a valid and acceptable explanation.

Now, I just copied this commit message.

> 
>> The potential future change mentioned in the commit messages of
>> 72fc64c68decf119466 and 98b16a09861aa85d6 happened in commit
>> af503716ac1444db61d80 ("i2c: core: report OF style module alias for
>> devices registered via OF").  The commit message of
>> af503716ac1444db61d80 has a lot of details about the change being made,
>> and while it says that all in-tree drivers had been converted, it looks
>> like some of them, like tmp401, were missed.
>> 
> 
> And this is the missing link. If you provide that information
> in the commit log I have no problems. Please also provide a Fixes:
> tag.
> 
> Fixes: af503716ac14 ("i2c: core: report OF style module alias for 
> devices registered via OF")

It is added in v3

> 
> Thanks,
> Guenter
> 
>>> The above is no evidence; that would require a log output on an affected
>>> system showing that the sensors are not or no longer longer instantiated.
>> 
>> A log would simply show nothing happening so that's probably not going
>> to be that useful, but here is what the modaliases look like.  As you
>> can see, the modalias of the device in sysfs does not match any of the
>> alias patterns of the module without this patch:
>> 
>> $ cat /sys/bus/i2c/devices/4-004c/modalias
>> of:Ntemperature-sensorT<NULL>Cti,tmp431
>> 
>> modinfo without this patch:
>> 
>> $ modinfo ./modules/lib/modules/5.18.0-rc1/kernel/drivers/hwmon/tmp401.ko
>> filename:       /storage2/femfyra/linux-2.6/.roadtest/./modules/lib/modules/5.18.0-rc1/kernel/drivers/hwmon/tmp401.ko
>> license:        GPL
>> description:    Texas Instruments TMP401 temperature sensor driver
>> author:         Hans de Goede <hdegoede@...hat.com>
>> alias:          i2c:tmp435
>> alias:          i2c:tmp432
>> alias:          i2c:tmp431
>> alias:          i2c:tmp411
>> alias:          i2c:tmp401
>> depends:
>> intree:         Y
>> name:           tmp401
>> vermagic:       5.18.0-rc1 mod_unload
>> 
>> modinfo after this patch:
>> 
>> $ modinfo ./modules/lib/modules/5.18.0-rc1/kernel/drivers/hwmon/tmp401.ko
>> filename:       /storage2/femfyra/linux-2.6/./.roadtest/modules/lib/modules/5.18.0-rc1/kernel/drivers/hwmon/tmp401.ko
>> license:        GPL
>> description:    Texas Instruments TMP401 temperature sensor driver
>> author:         Hans de Goede <hdegoede@...hat.com>
>> alias:          i2c:tmp435
>> alias:          i2c:tmp432
>> alias:          i2c:tmp431
>> alias:          i2c:tmp411
>> alias:          i2c:tmp401
>> alias:          of:N*T*Cti,tmp435C*
>> alias:          of:N*T*Cti,tmp435
>> alias:          of:N*T*Cti,tmp432C*
>> alias:          of:N*T*Cti,tmp432
>> alias:          of:N*T*Cti,tmp431C*
>> alias:          of:N*T*Cti,tmp431
>> alias:          of:N*T*Cti,tmp411C*
>> alias:          of:N*T*Cti,tmp411
>> alias:          of:N*T*Cti,tmp401C*
>> alias:          of:N*T*Cti,tmp401
>> depends:
>> intree:         Y
>> name:           tmp401
>> vermagic:       5.18.0-rc1 mod_unload
> 

All commits have been fixed in v3, please review that one instead.