[PATCH] ftgmac100: return error in ftgmac100_alloc_rx_buf

[PATCH] ftgmac100: return error in ftgmac100_alloc_rx_buf

[Joel Stanley]

The error paths set err, but it's not returned.

I wondered if we should fix all of the callers to check the returned
value, but Ben explains why the code is this way:

> Most call sites ignore it on purpose. There's nothing we can do if
> we fail to get a buffer at interrupt time, so we point the buffer to
> the scratch page so the HW doesn't DMA into lalaland and lose the
> packet.
>
> The one call site that tests and can fail is the one used when brining
> the interface up. If we fail to allocate at that point, we fail the
> ifup. But as you noticed, I do have a bug not returning the error.

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Joel Stanley <joel@jms.id.au>
---
 drivers/net/ethernet/faraday/ftgmac100.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
index fce0aa4f78b7..33b5c8eb9961 100644
--- a/drivers/net/ethernet/faraday/ftgmac100.c
+++ b/drivers/net/ethernet/faraday/ftgmac100.c
@@ -392,7 +392,7 @@ static int ftgmac100_alloc_rx_buf(struct ftgmac100 *priv, unsigned int entry,
 	struct net_device *netdev = priv->netdev;
 	struct sk_buff *skb;
 	dma_addr_t map;
-	int err;
+	int err = 0;
 
 	skb = netdev_alloc_skb_ip_align(netdev, RX_BUF_SIZE);
 	if (unlikely(!skb)) {
@@ -428,7 +428,7 @@ static int ftgmac100_alloc_rx_buf(struct ftgmac100 *priv, unsigned int entry,
 	else
 		rxdes->rxdes0 = 0;
 
-	return 0;
+	return err;
 }
 
 static unsigned int ftgmac100_next_rx_pointer(struct ftgmac100 *priv,
-- 
2.13.3

Re: [PATCH] ftgmac100: return error in ftgmac100_alloc_rx_buf

[David Miller]

From: Joel Stanley <joel@jms.id.au>
Date: Tue, 25 Jul 2017 10:19:01 +0930

> The error paths set err, but it's not returned.
> 
> I wondered if we should fix all of the callers to check the returned
> value, but Ben explains why the code is this way:
> 
>> Most call sites ignore it on purpose. There's nothing we can do if
>> we fail to get a buffer at interrupt time, so we point the buffer to
>> the scratch page so the HW doesn't DMA into lalaland and lose the
>> packet.
>>
>> The one call site that tests and can fail is the one used when brining
>> the interface up. If we fail to allocate at that point, we fail the
>> ifup. But as you noticed, I do have a bug not returning the error.
> 
> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Signed-off-by: Joel Stanley <joel@jms.id.au>

Applied, thanks.