netdev - Re: [EXT] Re: [PATCH/RFC v2 net-next] ravb: unmap descriptors when freeing rings

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Date:   Thu, 12 Jan 2017 21:00:14 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Lino Sanfilippo <lsanfil@...vell.com>,
        Simon Horman <horms@...ge.net.au>
Cc:     David Miller <davem@...emloft.net>,
        Magnus Damm <magnus.damm@...il.com>, netdev@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [EXT] Re: [PATCH/RFC v2 net-next] ravb: unmap descriptors when
 freeing rings

On 01/12/2017 07:55 PM, Lino Sanfilippo wrote:

>>>>>> +
>>>>>> +    for (; priv->cur_tx[q] - priv->dirty_tx[q] > 0; priv->dirty_tx[q]++) {
>>>
>>> BTW: How can this work correctly when cur_tx wraps and dirty_tx is greater?
>>
>>    {cur|dirty}_tx never wrap.
>>
>
> Both values are 32 bit and AFAICS they are only incremented (and never reset or
> decremented).

    Yeah, sorry, O thought you mean the TX ring size wrapping.

> So what prevents them from wrapping every 2^32 processed tx descriptors? Am I
> missing
> something?

    The math should still work all right IIUC.

> Regards,
> Lino

MBR, Sergei