linux-kernel - Re: [PATCH net-next v3 07/10] net: Relocate dev_to_net

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Date:   Sun, 15 Jan 2017 09:20:06 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     netdev@...r.kernel.org, Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Gregory Clement <gregory.clement@...e-electrons.com>,
        Russell King <linux@...linux.org.uk>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        "David S. Miller" <davem@...emloft.net>,
        "moderated list:ARM SUB-ARCHITECTURES" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 07/10] net: Relocate dev_to_net_device() into
 core



On 01/15/2017 03:07 AM, Greg KH wrote:
> On Sat, Jan 14, 2017 at 01:47:10PM -0800, Florian Fainelli wrote:
>> dev_to_net_device() is moved from net/dsa/dsa.c to net/core/dev.c since
>> it going to be used by net/dsa/dsa2.c and the namespace of the function
>> justifies making it available to other users potentially.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> ---
>>  include/linux/netdevice.h |  2 ++
>>  net/core/dev.c            | 19 +++++++++++++++++++
>>  net/dsa/dsa.c             | 18 ------------------
>>  3 files changed, 21 insertions(+), 18 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index 97ae0ac513ee..6d021c37b774 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -4390,4 +4390,6 @@ do {								\
>>  #define PTYPE_HASH_SIZE	(16)
>>  #define PTYPE_HASH_MASK	(PTYPE_HASH_SIZE - 1)
>>  
>> +struct net_device *dev_to_net_device(struct device *dev);
>> +
>>  #endif	/* _LINUX_NETDEVICE_H */
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index ad5959e56116..7547e2ccc06b 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -8128,6 +8128,25 @@ const char *netdev_drivername(const struct net_device *dev)
>>  	return empty;
>>  }
>>  
>> +struct net_device *dev_to_net_device(struct device *dev)
>> +{
>> +	struct device *d;
>> +
>> +	d = device_find_class(dev, "net");
>> +	if (d) {
>> +		struct net_device *nd;
>> +
>> +		nd = to_net_dev(d);
>> +		dev_hold(nd);
>> +		put_device(d);
>> +
>> +		return nd;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +EXPORT_SYMBOL_GPL(dev_to_net_device);
> 
> This really isn't just a "struct device to net device cast" type
> function, (otherwise a simple container_of() would work).  You are
> walking the device tree and assuming it is in a specific order so that
> this function works.  You better document the hell out of this,
> otherwise people are going to try to use this and get very confused,
> very quickly...

Fair enough. Does that make it clearer how the device_find_class() is
used though? Maybe device_find_class() should be named
device_find_by_class_name() instead?
-- 
Florian