Re: [Qemu-devel] [PATCH] lan9118: Ignore write to MAC_VLAN1 register

[Atsushi Nemoto]

On Mon, 4 Apr 2011 20:15:30 +0200, Aurelien Jarno <address@hidden> wrote:
> Is it really safe ignoring write to this register? If yes, it's probably
> a good idea to explain why in a comment. In any case, if supporting this
> register is easy to do, it would be the best option.

I think it is safe.  Please see an updated comment below.

And though implementing this register might be possible, I suppose it
is not worth to supporting FrameTooLong detection, for now at least.

Thank you for comments.

>8---------------------------------------------------------------------
From: Atsushi Nemoto <address@hidden>
Date: Tue, 5 Apr 2011 23:12:07 +0900
Subject: [PATCH] lan9118: Ignore write to MAC_VLAN1 register

Since linux 2.6.38, smsc911x driver writes to VLAN1 registger.
Since this register only affects FrameTooLong detection, ignoring
write to this register should be safe.

Signed-off-by: Atsushi Nemoto <address@hidden>
---
 hw/lan9118.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/hw/lan9118.c b/hw/lan9118.c
index af6949f..2dc8d18 100644
--- a/hw/lan9118.c
+++ b/hw/lan9118.c
@@ -785,6 +785,12 @@ static void do_mac_write(lan9118_state *s, int reg, 
uint32_t val)
     case MAC_FLOW:
         s->mac_flow = val & 0xffff0000;
         break;
+    case MAC_VLAN1:
+        /* Writing to this register changes a condition for
+         * FrameTooLong bit in rx_status.  Since we do not set
+         * FrameTooLong anyway, just ignore write to this.
+         */
+        break;
     default:
         hw_error("lan9118: Unimplemented MAC register write: %d = 0x%x\n",
                  s->mac_cmd & 0xf, val);
-- 
1.5.6.5