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

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Date:	Wed, 9 Nov 2011 17:48:15 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Mark Lord <kernel@...savvy.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 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.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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