[PATCH] igb: Fix a test with HWTSTAMP_TX_ON

[PATCH] igb: Fix a test with HWTSTAMP_TX_ON

[Christophe JAILLET]

'HWTSTAMP_TX_ON' should be handled as a value, not as a bit mask.
The modified code should behave the same, because HWTSTAMP_TX_ON is 1
and no other possible values of 'tx_type' would match the test.
However, this is more future-proof, should other values be allowed one day.

See 'struct hwtstamp_config' in 'include/uapi/linux/net_tstamp.h'

This fixes a warning reported by smatch:
   igb_xmit_frame_ring() warn: bit shifter 'HWTSTAMP_TX_ON' used for logical '&'

Fixes: 26bd4e2db06be ("igb: protect TX timestamping from API misuse")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index c208753ff5b7..e945d1f7c7fe 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -5727,7 +5727,7 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
 		struct igb_adapter *adapter = netdev_priv(tx_ring->netdev);
 
-		if (adapter->tstamp_config.tx_type & HWTSTAMP_TX_ON &&
+		if (adapter->tstamp_config.tx_type == HWTSTAMP_TX_ON &&
 		    !test_and_set_bit_lock(__IGB_PTP_TX_IN_PROGRESS,
 					   &adapter->state)) {
 			skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
-- 
2.14.1


---
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Re: [PATCH] igb: Fix a test with HWTSTAMP_TX_ON

[Richard Cochran]

On Tue, Feb 06, 2018 at 08:47:59PM +0100, Christophe JAILLET wrote:
> 'HWTSTAMP_TX_ON' should be handled as a value, not as a bit mask.
> The modified code should behave the same, because HWTSTAMP_TX_ON is 1
> and no other possible values of 'tx_type' would match the test.
> However, this is more future-proof, should other values be allowed one day.

Nice catch, and I am going to introduce more tx_type values soon.

Thanks,
Richard

RE: [PATCH] igb: Fix a test with HWTSTAMP_TX_ON

[Brown, Aaron F]

> From: netdev-owner@vger.kernel.org [mailto:netdev-
> owner@vger.kernel.org] On Behalf Of Christophe JAILLET
> Sent: Tuesday, February 6, 2018 11:48 AM
> To: Kirsher, Jeffrey T <jeffrey.t.kirsher@intel.com>
> Cc: intel-wired-lan@lists.osuosl.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; kernel-janitors@vger.kernel.org; Christophe
> JAILLET <christophe.jaillet@wanadoo.fr>
> Subject: [PATCH] igb: Fix a test with HWTSTAMP_TX_ON
> 
> 'HWTSTAMP_TX_ON' should be handled as a value, not as a bit mask.
> The modified code should behave the same, because HWTSTAMP_TX_ON is
> 1
> and no other possible values of 'tx_type' would match the test.
> However, this is more future-proof, should other values be allowed one day.
> 
> See 'struct hwtstamp_config' in 'include/uapi/linux/net_tstamp.h'
> 
> This fixes a warning reported by smatch:
>    igb_xmit_frame_ring() warn: bit shifter 'HWTSTAMP_TX_ON' used for
> logical '&'
> 
> Fixes: 26bd4e2db06be ("igb: protect TX timestamping from API misuse")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Tested-by: Aaron Brown <aaron.f.brown@intel.com>