RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
> return (TX_RING_SIZE - (bp->tx_head - bp->tx_tail) & (TX_RING_SIZE - > 1)); Is equivalent to: return (bp->tx_tail - bp->tx_head) & (TX_RING_SIZE - 1)); David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On 10/31/2012 10:59 AM, Nicolas Ferre :
> On 10/30/2012 07:22 PM, Håvard Skinnemoen :
>> On Tue, Oct 30, 2012 at 4:12 AM, David Laight
>> wrote:
Instead of masking head and tail every time we increment them, just let
them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of
messing
this up.
>>> ...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
+}
>>>
>>> That one doesn't look quite right to me.
>>> Surely it should be masking with 'TX_RING_SIZE - 1'
>>
>> Why is that? head and tail can never be more than TX_RING_SIZE apart,
>> so it shouldn't make any difference.
>
> Absolutely.
Well not so absolute, after having thinking twice ;-)
We should move to:
static unsigned int macb_tx_ring_avail(struct macb *bp)
{
return (TX_RING_SIZE - (bp->tx_head - bp->tx_tail) & (TX_RING_SIZE -
1));
}
Thanks David!
(sorry for the noise) Bye,
--
Nicolas Ferre
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
> On Tue, Oct 30, 2012 at 4:12 AM, David Laight wrote:
> >> Instead of masking head and tail every time we increment them, just let
> >> them
> >> wrap through UINT_MAX and mask them when subscripting. Add simple accessor
> >> functions to do the subscripting properly to minimize the chances of
> >> messing
> >> this up.
> > ...
> >> +static unsigned int macb_tx_ring_avail(struct macb *bp)
> >> +{
> >> + return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
> >> +}
> >
> > That one doesn't look quite right to me.
> > Surely it should be masking with 'TX_RING_SIZE - 1'
>
> Why is that? head and tail can never be more than TX_RING_SIZE apart,
> so it shouldn't make any difference.
It's a ring buffer (I presume) the pointers can be in either order.
David
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On 10/30/2012 07:22 PM, Håvard Skinnemoen :
> On Tue, Oct 30, 2012 at 4:12 AM, David Laight wrote:
>>> Instead of masking head and tail every time we increment them, just let them
>>> wrap through UINT_MAX and mask them when subscripting. Add simple accessor
>>> functions to do the subscripting properly to minimize the chances of messing
>>> this up.
>> ...
>>> +static unsigned int macb_tx_ring_avail(struct macb *bp)
>>> +{
>>> + return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
>>> +}
>>
>> That one doesn't look quite right to me.
>> Surely it should be masking with 'TX_RING_SIZE - 1'
>
> Why is that? head and tail can never be more than TX_RING_SIZE apart,
> so it shouldn't make any difference.
Absolutely.
Best regards,
--
Nicolas Ferre
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On 10/30/2012 07:22 PM, Håvard Skinnemoen :
On Tue, Oct 30, 2012 at 4:12 AM, David Laight david.lai...@aculab.com wrote:
Instead of masking head and tail every time we increment them, just let them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of messing
this up.
...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp-tx_head - bp-tx_tail);
+}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.
Absolutely.
Best regards,
--
Nicolas Ferre
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On Tue, Oct 30, 2012 at 4:12 AM, David Laight david.lai...@aculab.com wrote:
Instead of masking head and tail every time we increment them, just let
them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of
messing
this up.
...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp-tx_head - bp-tx_tail);
+}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.
It's a ring buffer (I presume) the pointers can be in either order.
David
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On 10/31/2012 10:59 AM, Nicolas Ferre :
On 10/30/2012 07:22 PM, Håvard Skinnemoen :
On Tue, Oct 30, 2012 at 4:12 AM, David Laight david.lai...@aculab.com
wrote:
Instead of masking head and tail every time we increment them, just let
them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of
messing
this up.
...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp-tx_head - bp-tx_tail);
+}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.
Absolutely.
Well not so absolute, after having thinking twice ;-)
We should move to:
static unsigned int macb_tx_ring_avail(struct macb *bp)
{
return (TX_RING_SIZE - (bp-tx_head - bp-tx_tail) (TX_RING_SIZE -
1));
}
Thanks David!
(sorry for the noise) Bye,
--
Nicolas Ferre
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
return (TX_RING_SIZE - (bp-tx_head - bp-tx_tail) (TX_RING_SIZE - 1)); Is equivalent to: return (bp-tx_tail - bp-tx_head) (TX_RING_SIZE - 1)); David -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On Tue, Oct 30, 2012 at 4:12 AM, David Laight wrote:
>> Instead of masking head and tail every time we increment them, just let them
>> wrap through UINT_MAX and mask them when subscripting. Add simple accessor
>> functions to do the subscripting properly to minimize the chances of messing
>> this up.
> ...
>> +static unsigned int macb_tx_ring_avail(struct macb *bp)
>> +{
>> + return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
>> +}
>
> That one doesn't look quite right to me.
> Surely it should be masking with 'TX_RING_SIZE - 1'
Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.
Havard
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
> Instead of masking head and tail every time we increment them, just let them
> wrap through UINT_MAX and mask them when subscripting. Add simple accessor
> functions to do the subscripting properly to minimize the chances of messing
> this up.
...
> +static unsigned int macb_tx_ring_avail(struct macb *bp)
> +{
> + return TX_RING_SIZE - (bp->tx_head - bp->tx_tail);
> +}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
David
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
RE: [PATCH v3 06/10] net/macb: clean up ring buffer logic
Instead of masking head and tail every time we increment them, just let them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of messing
this up.
...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp-tx_head - bp-tx_tail);
+}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
David
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v3 06/10] net/macb: clean up ring buffer logic
On Tue, Oct 30, 2012 at 4:12 AM, David Laight david.lai...@aculab.com wrote:
Instead of masking head and tail every time we increment them, just let them
wrap through UINT_MAX and mask them when subscripting. Add simple accessor
functions to do the subscripting properly to minimize the chances of messing
this up.
...
+static unsigned int macb_tx_ring_avail(struct macb *bp)
+{
+ return TX_RING_SIZE - (bp-tx_head - bp-tx_tail);
+}
That one doesn't look quite right to me.
Surely it should be masking with 'TX_RING_SIZE - 1'
Why is that? head and tail can never be more than TX_RING_SIZE apart,
so it shouldn't make any difference.
Havard
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
