On 21-12-26 23:12:08, Matthias-Christian Ott wrote: > The D-Link DSB-650TX (2001:4002) is unable to receive Ethernet frames that are > longer than 1518 octets, for example, Ethernet frames that contain 802.1Q VLAN > tags. > > The frames are sent to the pegasus driver via USB but the driver discards them > because they have the Long_pkt field set to 1 in the received status report. > The function read_bulk_callback of the pegasus driver treats such received > "packets" (in the terminology of the hardware) as errors but the field simply > does just indicate that the Ethernet frame (MAC destination to FCS) is longer > than 1518 octets. > > It seems that in the 1990s there was a distinction between "giant" (> 1518) > and "runt" (< 64) frames and the hardware includes flags to indicate this > distinction. It seems that the purpose of the distinction "giant" frames was > to not allow infinitely long frames due to transmission errors and to allow > hardware to have an upper limit of the frame size. However, the hardware > already has such limit with its 2048 octet receive buffer and, therefore, > Long_pkt is merely a convention and should not be treated as a receive error. > > Actually, the hardware is even able to receive Ethernet frames with 2048 > octets which exceeds the claimed limit frame size limit of the driver of 1536 > octets (PEGASUS_MTU). 2048 is not mentioned anywhere in both, adm8511 and adm8515 documents. In the latter I found 1638 as max packet length, but that's not the default. The default is 1528 and i don't feel like changing it without further investigation. Thus, i assume it is safe to change PEGASUS_MTU to 1528 for the moment. VLAN frames have 4 additional bytes so we aren't breaking neither pegasus I nor pegasus II devices. If you're going to make ver 3 of this change, you might as well modify PEGASUS_MTU in pegasus.h as a separate patch within the same series. Petko > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Matthias-Christian Ott <ott@xxxxxxxxx> > --- > V1 -> V2: Included "Fixes:" tag > > drivers/net/usb/pegasus.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c > index 140d11ae6688..2582daf23015 100644 > --- a/drivers/net/usb/pegasus.c > +++ b/drivers/net/usb/pegasus.c > @@ -499,11 +499,11 @@ static void read_bulk_callback(struct urb *urb) > goto goon; > > rx_status = buf[count - 2]; > - if (rx_status & 0x1e) { > + if (rx_status & 0x1c) { > netif_dbg(pegasus, rx_err, net, > "RX packet error %x\n", rx_status); > net->stats.rx_errors++; > - if (rx_status & 0x06) /* long or runt */ > + if (rx_status & 0x04) /* runt */ > net->stats.rx_length_errors++; > if (rx_status & 0x08) > net->stats.rx_crc_errors++; > -- > 2.30.2 > >