linux-kernel - Re: [PATCH v3 3/3] EDAC: nuvoton: Add NPCM memory controller driver

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Date:   Mon, 14 Mar 2022 08:35:14 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Avi Fishman <avifishman70@...il.com>
Cc:     Medad CChien <medadyoung@...il.com>, rric@...nel.org,
        James Morse <james.morse@....com>, tony.luck@...el.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Rob Herring <robh+dt@...nel.org>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Patrick Venture <venture@...gle.com>, KWLIU@...oton.com,
        YSCHU@...oton.com, JJLIU0@...oton.com, KFTING@...oton.com,
        Tomer Maimon <tmaimon77@...il.com>,
        Tali Perry <tali.perry1@...il.com>, ctcchien@...oton.com,
        linux-edac <linux-edac@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>
Subject: Re: [PATCH v3 3/3] EDAC: nuvoton: Add NPCM memory controller driver

On 13/03/2022 21:22, Avi Fishman wrote:
> On Fri, Mar 11, 2022 at 11:15 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...onical.com> wrote:
>>
>> On 11/03/2022 02:42, Medad CChien wrote:
>>> Add support for Nuvoton NPCM SoC.
>>>
>>> Signed-off-by: Medad CChien <ctcchien@...oton.com>
>>> ---
>>>  drivers/edac/Kconfig     |   9 +
>>>  drivers/edac/Makefile    |   1 +
>>>  drivers/edac/npcm_edac.c | 714 +++++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 724 insertions(+)
>>>  create mode 100644 drivers/edac/npcm_edac.c
>>>
>>> diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
>>> index 58ab63642e72..757e1d160640 100644
>>> --- a/drivers/edac/Kconfig
>>> +++ b/drivers/edac/Kconfig
>>> @@ -539,4 +539,13 @@ config EDAC_DMC520
>>>         Support for error detection and correction on the
>>>         SoCs with ARM DMC-520 DRAM controller.
>>>
>>> +config EDAC_NPCM
>>> +     tristate "Nuvoton NPCM DDR Memory Controller"
>>> +     depends on ARCH_NPCM
>>
>> || COMPILE_TEST
>> (and test if it compiles)
>>
>> (...)
>>
>>> +
>>> +MODULE_DEVICE_TABLE(of, npcm_edac_of_match);
>>> +
>>> +static int npcm_edac_mc_probe(struct platform_device *pdev)
>>> +{
>>> +     const struct npcm_edac_platform_data *npcm_chip;
>>> +     struct device *dev = &pdev->dev;
>>> +     struct edac_mc_layer layers[1];
>>> +     const struct of_device_id *id;
>>> +     struct priv_data *priv_data;
>>> +     struct mem_ctl_info *mci;
>>> +     struct resource *res;
>>> +     void __iomem *reg;
>>> +     int ret = -ENODEV;
>>> +     int irq;
>>> +
>>> +     id = of_match_device(npcm_edac_of_match, &pdev->dev);
>>> +     if (!id)
>>> +             return -ENODEV;
>>
>> Why do you need it? How such case is even possible?
>>
>>> +
>>> +     npcm_chip = of_device_get_match_data(&pdev->dev);
>>> +     if (!npcm_chip)
>>> +             return -ENODEV;
>>
>> I wonder, how is it possible to have here NULL?
>>
> Both of_match_device() and of_device_get_match_data() can return NULL,
> are we missing something?

I think your driver is OF-only, right? If yes, how is it possible to be
here in probe() (meaning: being matched by of_device_id) and a few lines
later do not match the same of_device_id?

Best regards,
Krzysztof