netdev - RE: [PATCH] gianfar: Fix warnings when built on 64-bit

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Date:	Wed, 29 Jul 2015 11:03:29 +0000
From:	Manoil Claudiu <claudiu.manoil@...escale.com>
To:	Arnd Bergmann <arnd@...db.de>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Scott Wood <scottwood@...escale.com>
Subject: RE: [PATCH] gianfar: Fix warnings when built on 64-bit

> -----Original Message-----
> From: Arnd Bergmann [mailto:arnd@...db.de]
> Sent: Wednesday, July 29, 2015 11:02 AM
> To: linuxppc-dev@...ts.ozlabs.org; netdev@...r.kernel.org; Manoil Claudiu-
> B08782; Wood Scott-B07421
> Subject: Re: [PATCH] gianfar: Fix warnings when built on 64-bit
> 
> On Wednesday 29 July 2015 00:24:37 Scott Wood wrote:
> 
> > Alternatively, if there's a desire to not mess with this code (I don't
> > know how to trigger this code path to test it), this driver should be
> > given dependencies that ensure that it only builds on 32-bit.
> 
[...]

> > @@ -2964,8 +2967,13 @@ int gfar_clean_rx_ring(struct gfar_priv_rx_q
> *rx_queue, int rx_work_limit)
> >  		gfar_init_rxbdp(rx_queue, bdp, bufaddr);
> >
> >  		/* Update Last Free RxBD pointer for LFC */
> > -		if (unlikely(rx_queue->rfbptr && priv->tx_actual_en))
> > -			gfar_write(rx_queue->rfbptr, (u32)bdp);
> > +		if (unlikely(rx_queue->rfbptr && priv->tx_actual_en)) {
> > +			u32 bdp_dma;
> > +
> > +			bdp_dma = lower_32_bits(rx_queue-
> >rx_bd_dma_base);
> > +			bdp_dma += (uintptr_t)bdp - (uintptr_t)base;
> > +			gfar_write(rx_queue->rfbptr, bdp_dma);
> > +		}
> >
> >  		/* Update to the next pointer */
> >  		bdp = next_bd(bdp, base, rx_queue->rx_ring_size);
> 
> You are fixing two problems here: the warning about a size cast, and
> the fact that the driver is using the wrong pointer. I'd suggest
> explaining it in the changelog.
> 

What would be the wrong pointer here? "base"?
"base" is " rx_queue->rx_bd_base".

> Note that we normally rely on void pointer arithmetic in the kernel, so
> I'd write it without the uintptr_t casts as
> 
> 	bdp_dma = lower_32_bits(rx_queue->rx_bd_dma_base + (base -
> bdp));

I think you mean: (bdp-base)

Claudiu
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