linux-kernel - Re: [RFC PATCH] char: misc: Init misc->list in a safe way

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Message-ID: <CAAfSe-uUvkqvp4fXq-rjUJey-Y1m39J11DnGtHgH4MApAu5y0Q@mail.gmail.com>
Date:   Thu, 29 Jun 2017 14:54:23 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Orson Zhai (翟京) 
        <orson.zhai@...eadtrum.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Zhongping Tan (谭中平) 
        <Zhongping.Tan@...eadtrum.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        songhe.wei@...eadtrum.com
Subject: Re: [RFC PATCH] char: misc: Init misc->list in a safe way

Hi Greg,

On 28 June 2017 at 19:21, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> On Wed, Jun 28, 2017 at 12:34:28PM +0200, Arnd Bergmann wrote:
>> On Wed, Jun 28, 2017 at 7:18 AM, Greg Kroah-Hartman
>> <gregkh@...uxfoundation.org> wrote:
>> > On Wed, Jun 28, 2017 at 09:54:32AM +0800, Orson Zhai wrote:
>> >> We found the device is "fm". We highly suspect that fm driver call
>> >> misc_register twice and reinitialize list to make ->pre & ->next
>> >> pointing to himself.
>> >>
>> >> Meanwhile, we checked fm driver and found nothing obviously wrong in the code.
>> >
>> > Do you have a pointer to this driver?  Is it in the kernel tree?
>>
>> I found a version of some spreadtrum FM driver in the sources for the
>> Samsung Galaxy
>> J3, this is the driver https://pastebin.com/p7Y7xQNE
>
> Ah nice, Orson, is that the driver?

For some unknown reason, Orson was missing in this list :)
I'm adding him back.

This is not the latest version of our FM driver.  You can find the
version we're using within Spreadtrum here [1], and the kernel version
we're using is v4.4.49.

>
> Any objection for me adding it to the kernel tree so we can fix up the

We have no objection to adding this driver to the kernel tree.

> issues that Arnd points out in it (not to mention the coding style
> issues...)

Actually, our FM driver owner Songhe (cc'ed here) had checked by
adding logs, the probe() function was called only once during the
whole initialization.
They have made a few times of review on the driver and haven't found
any suspicion in it, so Zhongping thought out the solution you can see
in this patch.

Many thanks for your help,
Chunyan

>
> thanks,
>
> greg k-h