Daniele Palmas <dnlplm@xxxxxxxxx> writes: > Testing Telit LM940 with ICMP packets > 14552 bytes revealed that > the modem needs FLAG_SEND_ZLP to properly work, otherwise the cdc > mbim data interface won't be anymore responsive. > > Signed-off-by: Daniele Palmas <dnlplm@xxxxxxxxx> Acked-by: Bjørn Mork <bjorn@xxxxxxx> Should have thought of this... I noticed your discussion, but couldn't reproduce the issues myself. This explains why. Do you happen to know if the device announces larger buffers than the driver wants to use, or if this happens with the max sized buffers too? You can easily check these values by comparing dwNtbInMaxSize and dwNtbOutMaxSize (device maximum values) with rx_max and tx_max (neogtiated values) using e.g grep . /sys/class/net/wwan0/cdc_ncm/* It has never been 100% clear to me whether we should send the ZLP by default if we've negotiated a smaller than max buffer. But the ZLP ought to be redundant in any case, since the device knows the negotiated buffer size. So I do believe our current interpretation makes sense. Not that it matters. There are obviously more than enough device implementations violating this requirement to make it completely pointless. Bjørn -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
