linux-kernel - Re: [PATCH v2 01/10] mfd: intel_soc_pmic: Fix an error handling path in intel_soc_pmic_i2c

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Message-ID: <76186bb4-63ac-857f-f9f6-d020ca44c380@redhat.com>
Date:   Mon, 1 Aug 2022 12:53:43 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lee Jones <lee@...nel.org>, Andy Shevchenko <andy@...nel.org>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v2 01/10] mfd: intel_soc_pmic: Fix an error handling path
 in intel_soc_pmic_i2c_probe()

Hi,

On 8/1/22 12:38, Andy Shevchenko wrote:
> On Mon, Aug 1, 2022 at 11:52 AM Hans de Goede <hdegoede@...hat.com> wrote:
>> On 8/1/22 11:29, Andy Shevchenko wrote:
>>> On Mon, Aug 1, 2022 at 11:14 AM Andy Shevchenko
>>> <andy.shevchenko@...il.com> wrote:
>>>> On Mon, Aug 1, 2022 at 10:43 AM Hans de Goede <hdegoede@...hat.com> wrote:
>>>>> On 7/31/22 22:12, Andy Shevchenko wrote:
> 
> ...
> 
>>>>> Note alternatively we could just move the pwm_add_table() to just before the "return 0",
>>>>> there is no strict ordering between adding the mfd devices and the pwm_add_table()
>>>>> (the pwm device only becomes available after the pwm-driver has bound to the mfd
>>>>> instantiated platform device which happens later).
>>>
>>> Just to be sure... How is it guaranteed that that happens later?
>>
>> Ah you are right, it could happen immediately if the driver is builtin and
>> has already registered (if the PWM driver is a module, as it is on Fedora,
>> then the driver will only bind once the module is loaded).
>>
>> Regardless there are no ordering guarantees between the probe() function of
>> intel_soc_pmic and the consumer of the PWM device, so the consumer must
>> be prepared to deal with the lookup not being present yet when its probe()
>> function runs (*).
> 
> Would be nice to have, but isn't it the issue with all lookup tables
> so far, e.g. consumers of GPIO ones are also affected the very same
> way?
> 
>> *) ATM this is actually an unsolved problem and this works only because the PMIC
>> drivers are builtin and i915, which consumes the PWM for backlight control
>> is a module. Swapping the order does not impact this.
> 
> Even so, I think we can't change order right now because the issue is
> much broader.

Ok, lets go with the original v2 1/10 patch then. In that case, you
may add my:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

to the original v2 1/10 patch.

Regards,

Hans