netdev - Re: [PATCH] drivers/net/usb/asix: resync from vendor's copy

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Message-ID: <4EBAC4E2.70808@teksavvy.com>
Date:	Wed, 09 Nov 2011 13:22:26 -0500
From:	Mark Lord <kernel@...savvy.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers/net/usb/asix:  resync from vendor's copy

On 11-11-09 12:48 PM, Ben Hutchings wrote:
> On Wed, 2011-11-09 at 12:40 -0500, Mark Lord wrote:
>> On 11-11-09 12:31 PM, Ben Hutchings wrote:
>>> On Wed, 2011-11-09 at 12:20 -0500, Mark Lord wrote:
>>>> On 11-11-09 11:57 AM, Mark Lord wrote:
>>>>> On 11-11-09 11:47 AM, Mark Lord wrote:
>>>>> ..
>>>>>> Note:  I'm looking at smsc95xx.c and smsc75xx.c for examples,
>>>>>> and they both have the same problem I'll have here:
>>>>>>
>>>>>> How to update the csum settings atomically.
>>>>>> A spinlock is no good, because config register access is over USB.
>>>>>
>>>>> Nevermind.. a slight change in the logic and all is well again.
>>>> ..
>>>>
>>>> Or even simpler (below).  I don't think this method requires any
>>>> extra locking, but I'm still open to persuasion.  :)
>>>
>>> Looks reasonable, but...
>>>
>>>> static int ax88772b_set_features(struct net_device *netdev, u32 features)
>>>> {
>>>>         struct usbnet *dev = netdev_priv(netdev);
>>>>         struct ax88772b_data *priv = (struct ax88772b_data *)dev->driver_priv;
>>>>         u16 tx_csum = 0, rx_csum = 0;
>>>>
>>>>         priv->features = features & (NETIF_F_HW_CSUM | NETIF_F_RXCSUM);
>>>
>>> ...why do you need priv->features at all?
>>
>>
>> There's code elsewhere that takes action under some conditions
>> based on the current setting of the NETIF_F_RXCSUM flag.
>>
>> I don't claim to fully understand what's going on,
>> but it doesn't care much about races on set/clear of the flag.
> 
> And it can use dev->features.

Oh, is that kosher?    Looks great to me!


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