Re: [Qemu-devel] [PATCH] fix the return value of rtl8139_can_receive()

[Kevin Wolf <kwolf@redhat.com>]

Am 16.06.2011 10:23, schrieb Wen Congyang:
> If rtl8139_can_receive() returns 1, it means that the nic can receive packet,
> otherwise, it means the nic can not receive packet.
> 
> If !s->clock_enabled or !rtl8139_receiver_enabled(s), it means that the nic
> can not receive packet. So the return value should be 0, not 1.
> 
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> 
> ---
>  hw/rtl8139.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/rtl8139.c b/hw/rtl8139.c
> index 2f8db58..9084678 100644
> --- a/hw/rtl8139.c
> +++ b/hw/rtl8139.c
> @@ -810,9 +810,9 @@ static int rtl8139_can_receive(VLANClientState *nc)
>  
>      /* Receive (drop) packets if card is disabled.  */
>      if (!s->clock_enabled)
> -      return 1;
> +      return 0;
>      if (!rtl8139_receiver_enabled(s))
> -      return 1;
> +      return 0;
>  
>      if (rtl8139_cp_receiver_enabled(s)) {
>          /* ??? Flow control not implemented in c+ mode.

NACK.

The old behaviour is clearly intentional. IIRC, can_receive() returning
0 means that the packet is kept in a queue and qemu tries to deliver it
later. For a disabled receiver, what I would expect is that it should
just drop the packets. This is what this code does by returning 1 in
can_receive() and then return -1 without processing the packet in receive().

That said, e1000 has a check for (s->mac_reg[RCTL] & E1000_RCTL_EN) in
can_receive. Should it be changed or is there a reason behind it? If
there is, we may as well change rtl8139, but it definitely needs a
better justification.

Kevin