diff mbox

WAN: bit and/or confusion

Message ID 4A8D57F8.1050106@gmail.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

roel kluin Aug. 20, 2009, 2:04 p.m. UTC 
Fix the tests that check whether Frame* bits are not set

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
---

>> -		else if (!(skb->data[pkt_len] | ~(FrameVfr | FrameRab)))
>> +		else if (!(skb->data[pkt_len] & (FrameVfr | FrameRab)))
>>  			dev->stats.rx_length_errors++;
> 
> This test requires both FrameVfr and FrameRab to be true (zero). Perhaps
> it should be:
> 
>> +		else if ((skb->data[pkt_len] & (FrameVfr | FrameRab)) != FrameVfr | FrameRab)

Ok, Francois Romieu, could you test this?

>>  		else
>>  			dev->stats.rx_errors++;
> 
> rx_errors is incremented only on remaining errors. I think most drivers
> increment rx_errors on all RX errors, and simultaneously rx_*_errors
> when needed.
> 
> 
> Perhaps something like the following should be better?
> 
> 		u8 status = ~skb->data[pkt_len];
> 
> 		if (status == 0)
> 			looks_good...;
> 		else {
> 			if (status & FrameRab)
> 				...
> 			if (status & FrameVfr)
> 				...
> 			etc.
> 			rx_errors++;
> 		}

I don't understand your suggestion - why status == 0? doesn't the patch
below do what you want instead?

Roel

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Comments

Krzysztof Halasa Aug. 20, 2009, 2:25 p.m. UTC | #1 
Roel Kluin <roel.kluin@gmail.com> writes:

>> Perhaps something like the following should be better?
>> 
>> 		u8 status = ~skb->data[pkt_len];
>> 
>> 		if (status == 0)
>> 			looks_good...;
>> 		else {
>> 			if (status & FrameRab)
>> 				...
>> 			if (status & FrameVfr)
>> 				...
>> 			etc.
>> 			rx_errors++;
>> 		}
>
> I don't understand your suggestion - why status == 0? doesn't the patch
> below do what you want instead?

Because I think (didn't read the manual) that these (inverted) bits
represent specific errors. So I suggested inverting them, then treating
as separate error bits, it should be easier to read.

That's only a suggestion of course (unless someone sends me the/a card -
non-returnable "donations" only please - and I can work on it
personally).

IOW all (inverted) bits = 1 => all bits zero after inversion => no
errors. This changes functionality a bit, and would need to be checked.
Otherwise, you could test: if ((status & FrameOk) == 0) then looks_good().

> diff --git a/drivers/net/wan/dscc4.c b/drivers/net/wan/dscc4.c
> index 8face5d..88534b6 100644
> --- a/drivers/net/wan/dscc4.c
> +++ b/drivers/net/wan/dscc4.c
> @@ -663,12 +663,12 @@ static inline void dscc4_rx_skb(struct dscc4_dev_priv *dpriv,
>  	} else {
>  		if (skb->data[pkt_len] & FrameRdo)
>  			dev->stats.rx_fifo_errors++;
> -		else if (!(skb->data[pkt_len] | ~FrameCrc))
> +		else if (!(skb->data[pkt_len] & FrameCrc))
>  			dev->stats.rx_crc_errors++;
> -		else if (!(skb->data[pkt_len] | ~(FrameVfr | FrameRab)))
> +		else if ((skb->data[pkt_len] & (FrameVfr | FrameRab)) !=
> +				FrameVfr | FrameRab)
>  			dev->stats.rx_length_errors++;
> -		else
> -			dev->stats.rx_errors++;
> +		dev->stats.rx_errors++;
>  		dev_kfree_skb_irq(skb);
>  	}
>  refill:

Guess it would do.
David Miller Aug. 31, 2009, 5:02 a.m. UTC | #2 
From: Roel Kluin <roel.kluin@gmail.com>
Date: Thu, 20 Aug 2009 16:04:40 +0200

> Fix the tests that check whether Frame* bits are not set
> 
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>

Applied to net-next-2.6, thanks.
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diff mbox

Patch

diff --git a/drivers/net/wan/dscc4.c b/drivers/net/wan/dscc4.c
index 8face5d..88534b6 100644
--- a/drivers/net/wan/dscc4.c
+++ b/drivers/net/wan/dscc4.c
@@ -663,12 +663,12 @@  static inline void dscc4_rx_skb(struct dscc4_dev_priv *dpriv,
 	} else {
 		if (skb->data[pkt_len] & FrameRdo)
 			dev->stats.rx_fifo_errors++;
-		else if (!(skb->data[pkt_len] | ~FrameCrc))
+		else if (!(skb->data[pkt_len] & FrameCrc))
 			dev->stats.rx_crc_errors++;
-		else if (!(skb->data[pkt_len] | ~(FrameVfr | FrameRab)))
+		else if ((skb->data[pkt_len] & (FrameVfr | FrameRab)) !=
+				FrameVfr | FrameRab)
 			dev->stats.rx_length_errors++;
-		else
-			dev->stats.rx_errors++;
+		dev->stats.rx_errors++;
 		dev_kfree_skb_irq(skb);
 	}
 refill: