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

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Message-ID: <20151031180751.GA490@electric-eye.fr.zoreil.com>
Date:	Sat, 31 Oct 2015 19:07:51 +0100
From:	Francois Romieu <romieu@...zoreil.com>
To:	Måns Rullgård <mans@...sr.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

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

-- 
Ueimor
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