linux-kernel - Re: Fwd: [PATCH net-next 1/2] lib: string: add strreplace

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Date:   Sun, 3 Mar 2019 19:47:29 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Fwd: [PATCH net-next 1/2] lib: string: add strreplace_nonalnum

On 03.03.2019 19:41, Greg Kroah-Hartman wrote:
> On Sun, Mar 03, 2019 at 07:32:53PM +0100, Heiner Kallweit wrote:
>> On 03.03.2019 19:15, Greg Kroah-Hartman wrote:
>>> On Sun, Mar 03, 2019 at 07:04:21PM +0100, Heiner Kallweit wrote:
>>>> On 03.03.2019 18:55, Greg Kroah-Hartman wrote:
>>>>> On Sun, Mar 03, 2019 at 06:47:32PM +0100, Heiner Kallweit wrote:
>>>>>> I submitted this through the netdev tree, maybe relevant for you as well.
>>>>>> See also here: https://marc.info/?t=155103900100003&r=1&w=2
>>>>>>
>>>>>> -------- Forwarded Message --------
>>>>>> Subject: [PATCH net-next 1/2] lib: string: add strreplace_nonalnum
>>>>>> Date: Sun, 3 Mar 2019 18:20:50 +0100
>>>>>> From: Heiner Kallweit <hkallweit1@...il.com>
>>>>>> To: Florian Fainelli <f.fainelli@...il.com>, Andrew Lunn <andrew@...n.ch>, David Miller <davem@...emloft.net>
>>>>>> CC: netdev@...r.kernel.org <netdev@...r.kernel.org>
>>>>>>
>>>>>> Add a new function strreplace_nonalnum that replaces all
>>>>>> non-alphanumeric characters. Such functionality is needed e.g. when a
>>>>>> string is supposed to be used in a sysfs file name. If '\0' is given
>>>>>> as new character then non-alphanumeric characters are cut. 
>>>>>
>>>>> sysfs doesn't have any such requirements, it can use whatever you want
>>>>> to give it for a filename.
>>>>>
>>>> Even a slash?
>>>
>>> Is a slash an illegal character for a file to have?  It's up to the vfs
>>> to care about this, don't force random parts of the kernel to care :)
>>>
>>>> HWMON drivers is an example where such functionality occurs open-coded.
>>>
>>> Is that data coming from userspace or from a kernel driver?
>>>
>> Usually from a kernel driver. That's what
>> Documentation/hwmon/hwmon-kernel-api.txt says:
> 
> Usually?  So userspace can set the name?
> 
I'm not sure about that.

>> All supported hwmon device registration functions only accept valid device
>> names. Device names including invalid characters (whitespace, '*', or '-')
>> will be rejected. The 'name' parameter is mandatory.
>>
>> The hwmon subsystem has an own function to check for such characters:
>> hwmon_is_bad_char()
> 
> It looks like hwmon is the only thing that cares about this then, why
> do you want to make this a common function?
> 
In phylib we have a similar issue, sysfs is broken if a PHY driver name
includes a slash, typically if some driver author uses "10 / 100 Mbit"
or similar.
IIRC for HWMON there has been some longer discussion about how to deal
with naming, I'd be curious to hear Guenter's opinion on the topic.

> thanks,
> 
> greg k-h
> 
Heiner