linux-kernel - Re: [PATCH v9 4/4] clk: meson: add sub MMC clock controller driver

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Message-ID: <f8f1c6c6-3805-6371-87ea-06fc14862625@amlogic.com>
Date:   Wed, 19 Jan 2022 10:55:38 +0800
From:   Liang Yang <liang.yang@...ogic.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Rob Herring <robh+dt@...nel.org>, <linux-clk@...r.kernel.org>
CC:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        XianWei Zhao <xianwei.zhao@...ogic.com>,
        Kelvin Zhang <kelvin.zhang@...ogic.com>,
        BiChao Zheng <bichao.zheng@...ogic.com>,
        YongHui Yu <yonghui.yu@...ogic.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 4/4] clk: meson: add sub MMC clock controller driver

Hi Stephen,

On 2022/1/19 10:22, Stephen Boyd wrote:
> [ EXTERNAL EMAIL ]
> 
> Quoting Liang Yang (2022-01-16 22:24:28)
>>
>>
>> On 2022/1/15 7:01, Stephen Boyd wrote:
>>> [ EXTERNAL EMAIL ]
>>>
>>> Quoting Liang Yang (2022-01-13 21:14:46)
>>>> On 2022/1/14 5:35, Stephen Boyd wrote:
>>>>> Quoting Liang Yang (2022-01-13 03:57:45)
>>>>>> diff --git a/drivers/clk/meson/mmc-clkc.c b/drivers/clk/meson/mmc-clkc.c
>>>>>> new file mode 100644
>>>>>> index 000000000000..f53977f61390
>>>>>> --- /dev/null
>>>>>> +++ b/drivers/clk/meson/mmc-clkc.c
>>>>>> @@ -0,0 +1,300 @@
>>> [..]
>>>>>> +
>>>>>> +static int mmc_clkc_probe(struct platform_device *pdev)
>>>>>> +{
>>>>>> +       struct clk_hw_onecell_data *onecell_data;
>>>>>> +       struct device *dev = &pdev->dev;
>>>>>> +       struct mmc_clkc_data *data;
>>>>>> +       struct regmap *map;
>>>>>> +       struct clk_regmap *clk, *core;
>>>>>> +       struct meson_sclk_div_data *div_data;
>>>>>> +
>>>>>> +       /*cast to drop the const in match->data*/
>>>>>
>>>>> Space after *, also why do we need to cast away const? The user of this
>>>>> pointer passes it all the way down to mmc_clkc_register_clk() which
>>>>> could take the data as const void pointer and decide to cast away const
>>>>> there.
>>>>
>>>> if use 'const' here, it  will report a warning:
>>>> drivers/clk/meson/mmc-clkc.c:224:7: error: assignment discards ‘const’
>>>> qualifier from pointer targe
>>>> t type [-Werror=discarded-qualifiers]
>>>>
>>>>      data = (const struct mmc_clkc_data *)of_device_get_match_data(dev);
>>>
>>> Of course. The type declaration up above needs const added to it.The parm of mmc_clkc_register_clk_with_parent(...., void *data) does not
>> have 'const', so make the type declaration cause a further 'const' cast
>> warning. Could i copy these infos just like below:
> 
> Why can't you push const down to the function that really cares to
> remove const?
em, it is really ok to me. i will fix it next version.
> 
> .