netdev - Re: [PATCH net-next-2.6 v2 1/2] can: add driver for Softing card

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Date:	Mon, 10 Jan 2011 14:31:12 +0100
From:	Kurt Van Dijck <kurt.van.dijck@....be>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	netdev@...r.kernel.org, socketcan-core@...ts.berlios.de
Subject: Re: [PATCH net-next-2.6 v2 1/2] can: add driver for Softing card

Wolfgang,

A few thoughts ...

On Wed, Jan 05, 2011 at 09:57:16PM +0100, Wolfgang Grandegger wrote:
> >  
> >  obj-y				+= usb/
> > +obj-y				+= softing/
> 
> Please use "obj-$(CONFIG_CAN_SOFTING)" here.
As I explained, softing does not depend on softing_cs or vice versa,
which makes "obj-$(CONFIG_CAN_SOFTING)" not right.

> > +	if (type != 0xffff) {
> > +		dev_alert(&card->pdev->dev, "firware starts with type 0x%04x\n",
> 
> Typo?
> 
??

> > +
> > +int softing_default_output(struct net_device *netdev)
> > +{
> > +	struct softing_priv *priv = netdev_priv(netdev);
> > +	struct softing *card = priv->card;
> > +
> > +	switch (priv->chip) {
> > +	case 1000:
> > +		if (card->pdat->generation < 2)
> > +			return 0xfb;
> > +		return 0xfa;
> > +	case 5:
> > +		return 0x60;
> > +	default:
> > +		return 0x40;
> > +	}
> > +}
> 
> Again, some magic constants.
The thing is, I didn't create those number, nor do I precisely know
which are the right ones, or how I would name those.
Since they're used one, I tought this would work.
> 
> > +	ret = netif_rx(skb);
> > +	if (ret == NET_RX_DROP)
> > +		++netdev->stats.rx_dropped;
> 
> Hm, I wonder if all Socket-CAN drivers should handle the return value of
> netif_rx that way?
> 
No, they should not.
After a seconds look, I'm a tiny little bit wrong here.
I should only increment rx_dropped when it's a real received message,
and not a virtual constructed one (bus crtls).
I moved this thing to the rx data handler.
Maybe, a common CAN rx function is usefull to properly deal with
the can_echo_skb & friends.

> 
> > +	priv->can.ctrlmode_supported =
> > +		CAN_CTRLMODE_3_SAMPLES;/* | CAN_CTRLMODE_BERR_REPORTING */;
> 
> Hm, any chance to support CAN_CTRLMODE_BERR_REPORTING? If not, please
> remove the comment.

I think I better try to write it properly without, and add error reporting
later, after serious testing of the error reporting on a softing card.

The primary goal now is get this driver in mainline kernel since PCMCIA
has been changing recently, and I found it hard to keep up. So, first things
first ...


Kurt
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