netdev - Re: [PATCH v4] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

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Message-ID: <yw1xd1vuc1zh.fsf@unicorn.mansr.com>
Date:	Sat, 31 Oct 2015 18:44:02 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v4] net: ethernet: add driver for Aurora VLSI NB8800 Ethernet controller

Francois Romieu <romieu@...zoreil.com> writes:

> Måns Rullgård <mans@...sr.com> :
>> Francois Romieu <romieu@...zoreil.com> writes:
> [...]
>> > It looks like it receives, then tries to allocate new resources. If so
>> > it may deplete the ring and you should instead consider allocating new
>> > resources first, then receive data if alloc + map suceeded.
>> 
>> The hardware receives a frame and stores it in the provided DMA buffer,
>> then raises an interrupt and moves on to the next buffer.  When a buffer
>> is handed over to the network stack, a new one has to take its place in
>> the DMA queue.  I'm not sure how you're suggesting this be done
>> differently.
>
> - The hardware raises an interrupt and moves on to the next packet
> - The driver allocates a new buffer - call it Bob - and maps it.
>   - If it succeeds
>     - The driver unmaps the received packet
>     - The driver hands the received packet to the network stack
>     - The driver hands Bob to the hardware
>   - It it fails
>     - The driver updates the dropped packet stats
>     - The driver recycles the received - yet non-unmapped - packet to the
>       hardware

Oh, I see.  That's better.

-- 
Måns Rullgård
mans@...sr.com
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