linux-kernel - Re: [PATCH v2 36/47] clk: mediatek: mt2712: Change Kconfig options to allow module build

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Message-ID: <dd25fddb-5c62-2dc7-6095-861499a5d21d@collabora.com>
Date:   Mon, 20 Feb 2023 10:01:27 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chen-Yu Tsai <wenst@...omium.org>
Cc:     mturquette@...libre.com, sboyd@...nel.org, matthias.bgg@...il.com,
        johnson.wang@...iatek.com, miles.chen@...iatek.com,
        chun-jie.chen@...iatek.com, daniel@...rotopia.org,
        fparent@...libre.com, msp@...libre.com, nfraprado@...labora.com,
        rex-bc.chen@...iatek.com, zhaojh329@...il.com,
        sam.shih@...iatek.com, edward-jw.yang@...iatek.com,
        yangyingliang@...wei.com, granquet@...libre.com,
        pablo.sun@...iatek.com, sean.wang@...iatek.com,
        chen.zhong@...iatek.com, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v2 36/47] clk: mediatek: mt2712: Change Kconfig options to
 allow module build

Il 17/02/23 16:19, Chen-Yu Tsai ha scritto:
> On Fri, Feb 17, 2023 at 7:25 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
>>
>> Il 17/02/23 05:24, Chen-Yu Tsai ha scritto:
>>> On Tue, Feb 14, 2023 at 9:42 PM AngeloGioacchino Del Regno
>>> <angelogioacchino.delregno@...labora.com> wrote:
>>>>
>>>> All of the mt2712 drivers have been converted to platform drivers!
>>>> Change the Kconfig options for all MT2712 clocks to tristate to allow
>>>> building all clock drivers as modules.
>>>>
>>>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>>> ---
>>>>    drivers/clk/mediatek/Kconfig | 16 ++++++++--------
>>>>    1 file changed, 8 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/clk/mediatek/Kconfig b/drivers/clk/mediatek/Kconfig
>>>> index b9c0a9e21cf1..45b7aea7648d 100644
>>>> --- a/drivers/clk/mediatek/Kconfig
>>>> +++ b/drivers/clk/mediatek/Kconfig
>>>> @@ -75,7 +75,7 @@ config COMMON_CLK_MT2701_G3DSYS
>>>>             This driver supports MediaTek MT2701 g3dsys clocks.
>>>>
>>>>    config COMMON_CLK_MT2712
>>>> -       bool "Clock driver for MediaTek MT2712"
>>>> +       tristate "Clock driver for MediaTek MT2712"
>>>
>>> Hmm... How does that work out if mt2712-apmixedsys is a
>>> builtin_platform_driver?
>>>
>>> ChenYu
>>
>> That doesn't. Thanks for catching that, I've added a .remove() callback
>> and changed it to module_platform_driver() for v3!
> 
> Actually, I thought that if it were built as a module, then the
> builtin_platform_driver would then expand to a module_init() without
> module_exit(). So it would become a loadable module that cannot be
> unloaded.
> 
> That was just looking at the header files, so I could be mistaken.
> 
> Side note: IIRC a missing .remove() driver callback doesn't actually
> block driver removal or unbinding.
> 

It doesn't, but we'd leak memory because of the kzalloc() that happened
at the beginning of the probe function... so adding the .remove() callback
was pretty much necessary :-)

Thanks,
Angelo

> ChenYu
>