linux-kernel - Re: [PATCH v2 1/1] mux: mux-core: Add NULL check for dev->of

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Date:   Sat, 8 Jul 2017 16:12:42 -0700
From:   "Kuppuswamy, Sathyanarayanan" <sathyaosid@...il.com>
To:     Peter Rosin <peda@...ntia.se>,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] mux: mux-core: Add NULL check for dev->of_node

Hi Peter,


On 7/8/2017 2:00 PM, Peter Rosin wrote:
> On 2017-07-07 23:46, sathyanarayanan.kuppuswamy@...ux.intel.com wrote:
>> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
>>
>> If dev->of_node is NULL, then calling mux_control_get()
>> function can lead to NULL pointer exception. So adding
>> a NULL check for dev->of_node.
>>
>> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> Do you have a driver that might call mux_control_get and not have any
> of_node?
For non-device tree drivers, this case is valid. I hit this issue when I 
was working on Intel USB MUX driver.
>   If not, I don't see the point of this check.
Since this is an API for other consumers, I think its better to have 
some sanity checks.

If a non device tree driver call this API , I think its better to fail 
with some error no instead of creating null pointer exception.
>
> Cheers,
> peda
>
>> ---
>>   drivers/mux/mux-core.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> Changes since v1:
>>   * Removed dummy new line.
>>
>> diff --git a/drivers/mux/mux-core.c b/drivers/mux/mux-core.c
>> index 90b8995..924c983 100644
>> --- a/drivers/mux/mux-core.c
>> +++ b/drivers/mux/mux-core.c
>> @@ -438,6 +438,9 @@ struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
>>   	int index = 0;
>>   	int ret;
>>   
>> +	if (!np)
>> +		return ERR_PTR(-ENODEV);
>> +
>>   	if (mux_name) {
>>   		index = of_property_match_string(np, "mux-control-names",
>>   						 mux_name);
>>