[PATCH net-next] 3c515: Fix warning when building

[PATCH net-next] 3c515: Fix warning when building

[Colin Rice]

Signed-off-by: Colin Rice <ricec2@rpi.edu>
---
 drivers/net/ethernet/3com/3c515.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/3com/3c515.c b/drivers/net/ethernet/3com/3c515.c
index 94c656f..33ffda4 100644
--- a/drivers/net/ethernet/3com/3c515.c
+++ b/drivers/net/ethernet/3com/3c515.c
@@ -1063,7 +1063,7 @@ static netdev_tx_t corkscrew_start_xmit(struct sk_buff *skb,
 #ifdef VORTEX_BUS_MASTER
 	if (vp->bus_master) {
 		/* Set the bus-master controller to transfer the packet. */
-		outl((int) (skb->data), ioaddr + Wn7_MasterAddr);
+		outl((size_t) (skb->data), ioaddr + Wn7_MasterAddr);
 		outw((skb->len + 3) & ~3, ioaddr + Wn7_MasterLen);
 		vp->tx_skb = skb;
 		outw(StartDMADown, ioaddr + EL3_CMD);
-- 
1.8.1.2

Re: [PATCH net-next] 3c515: Fix warning when building

[David Miller]

From: Colin Rice <ricec2@rpi.edu>
Date: Fri, 25 Oct 2013 21:59:46 +0000

> -		outl((int) (skb->data), ioaddr + Wn7_MasterAddr);
> +		outl((size_t) (skb->data), ioaddr + Wn7_MasterAddr);

outl() takes an "int" not a "size_t".   You're avoiding the warning,
but on 64-bit, for example, you're silently allowing the compiler
to accept chopping off the top 32-bits of the 64-bit pointer address
off.

The warning is valid, this code won't work in certain environments,
and killing the warning is just papering over the problem such that
it will never get addressed properly.

I'm not applying patches like this, sorry.

Re: [PATCH net-next] 3c515: Fix warning when building

[Ben Hutchings]

On Tue, 2013-10-29 at 00:03 -0400, David Miller wrote:
> From: Colin Rice <ricec2@rpi.edu>
> Date: Fri, 25 Oct 2013 21:59:46 +0000
> 
> > -		outl((int) (skb->data), ioaddr + Wn7_MasterAddr);
> > +		outl((size_t) (skb->data), ioaddr + Wn7_MasterAddr);
> 
> outl() takes an "int" not a "size_t".   You're avoiding the warning,
> but on 64-bit, for example, you're silently allowing the compiler
> to accept chopping off the top 32-bits of the 64-bit pointer address
> off.
> 
> The warning is valid, this code won't work in certain environments,
> and killing the warning is just papering over the problem such that
> it will never get addressed properly.
> 
> I'm not applying patches like this, sorry.

The driver is writing a virtual address as the DMA address.  The
hardware is an ISA device and will presumably ignore the top 8 bits,
thus doing the virt-to-bus conversion for us.  Very efficient - so long
as this runs on a PC with no more than 16 MB RAM.

For other chips with a DMA descriptor ring, the driver uses
isa_virt_to_bus() which is less efficient but no more correct.

Maybe the driver should just be deleted, as it doesn't look like it's
actually usable any more.

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.

Re: [PATCH net-next] 3c515: Fix warning when building

[Ben Hutchings]

On Tue, 2013-10-29 at 15:55 -0400, tedheadster wrote:
> Ben,
> 
>   it is useful for teaching the very things we're seeing discussed in
> this thread. Please don't delete it.

It's useful as a bad example?  Well you can always point to an old
version of the driver in git even after it's deleted.

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.

Re: [PATCH net-next] 3c515: Fix warning when building

[David Miller]

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Tue, 29 Oct 2013 19:31:57 +0000

> Maybe the driver should just be deleted, as it doesn't look like it's
> actually usable any more.

I'd like to agree, however I think the last time we had this
discussion someone said they were still using such a device :-)