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

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

[Atsushi Nemoto]

Since kernel 2.6.38, smsc911x driver writes to VLAN1 registger.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 hw/lan9118.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/hw/lan9118.c b/hw/lan9118.c
index af6949f..62aead3 100644
--- a/hw/lan9118.c
+++ b/hw/lan9118.c
@@ -785,6 +785,8 @@ 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:
+        break; /* just ignore */
     default:
         hw_error("lan9118: Unimplemented MAC register write: %d = 0x%x\n",
                  s->mac_cmd & 0xf, val);
-- 
1.5.6.5

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

[Aurelien Jarno]

On Tue, Mar 29, 2011 at 10:41:12PM +0900, Atsushi Nemoto wrote:
> Since kernel 2.6.38, smsc911x driver writes to VLAN1 registger.
> 
> Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
> ---
>  hw/lan9118.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/lan9118.c b/hw/lan9118.c
> index af6949f..62aead3 100644
> --- a/hw/lan9118.c
> +++ b/hw/lan9118.c
> @@ -785,6 +785,8 @@ 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:
> +        break; /* just ignore */
>      default:
>          hw_error("lan9118: Unimplemented MAC register write: %d = 0x%x\n",
>                   s->mac_cmd & 0xf, val);

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.


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net

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

[Atsushi Nemoto]

On Mon, 4 Apr 2011 20:15:30 +0200, Aurelien Jarno <aurelien@aurel32.net> 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 <anemo@mba.ocn.ne.jp>
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 <anemo@mba.ocn.ne.jp>
---
 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