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SubjectRe: [PATCH 1/7] Input: mtk-pmic-keys - check for NULL on of_match_device()
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Hi Dmitry,

Mattijs Korpershoek <mkorpershoek@baylibre.com> writes:

> Hi Dmitry,
>
> Dmitry Torokhov <dmitry.torokhov@gmail.com> writes:
>
>> Hi Mattijs,
>>
>> On Wed, Apr 28, 2021 at 06:42:13PM +0200, Mattijs Korpershoek wrote:
>>> mtk-pmic-keys being a child device of mt6397, it will always get probed
>>> when mt6397_probe() is called.
>>>
>>> This also happens when we have no device tree node matching
>>> mediatek,mt6397-keys.
>>
>> It sounds for me that creating a platform device instance in case where
>> we know need OF node, but do not have one, is wasteful. Can
>> mt6397-core.c and/or MFD core be adjusted to not do that.
>
> You are right. Maybe I can fix MFD core instead. I will look into it.
>
> Thanks for your review.
>>
>>>
>>> In that case, the mfd core warns us:
>>>
>>> [ 0.352175] mtk-pmic-keys: Failed to locate of_node [id: -1]
>>>
>>> Check return value from call to of_match_device()
>>> in order to prevent a NULL pointer dereference.
>>>
>>> In case of NULL print error message and return -ENODEV
>>>
>>> Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
>>> ---
>>> drivers/input/keyboard/mtk-pmic-keys.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/input/keyboard/mtk-pmic-keys.c b/drivers/input/keyboard/mtk-pmic-keys.c
>>> index 62391d6c7da6..12c449eed026 100644
>>> --- a/drivers/input/keyboard/mtk-pmic-keys.c
>>> +++ b/drivers/input/keyboard/mtk-pmic-keys.c
>>> @@ -247,6 +247,9 @@ static int mtk_pmic_keys_probe(struct platform_device *pdev)
>>> const struct of_device_id *of_id =
>>> of_match_device(of_mtk_pmic_keys_match_tbl, &pdev->dev);
>>>
>>> + if (!of_id)
>>> + return -ENODEV;
>>> +
>>
>> So if we make MFD/6396 core smarter we would not be needing this. I
>> guess there is still a possibility of someone stuffing "mtk-pmic-keys"
>> into "driver_override" attribute of a random platform device but I
>> wonder if we really need to take care of such scenarios...
It turns out it was possible to make 6397-core smarter.
I've submitted [1] to replace this patch.

Thanks again for your suggestion. Please let me know if I should add
your Suggested-by: in [1].

[1] https://patchwork.kernel.org/project/linux-mediatek/patch/20210429143811.2030717-1-mkorpershoek@baylibre.com/ instead
>>
>>> keys = devm_kzalloc(&pdev->dev, sizeof(*keys), GFP_KERNEL);
>>> if (!keys)
>>> return -ENOMEM;
>>> --
>>> 2.27.0
>>>
>>
>> Thanks.
>>
>> --
>> Dmitry

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