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What: /sys/class/net/<iface>/cdc_ncm/min_tx_pkt
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
The driver will pad NCM Transfer Blocks (NTBs) longer
than this to tx_max, allowing the device to receive
tx_max sized frames with no terminating short
packet. NTBs shorter than this limit are transmitted
as-is, without any padding, and are terminated with a
short USB packet.
Padding to tx_max allows the driver to transmit NTBs
back-to-back without any interleaving short USB
packets. This reduces the number of short packet
interrupts in the device, and represents a tradeoff
between USB bus bandwidth and device DMA optimization.
Set to 0 to pad all frames. Set greater than tx_max to
disable all padding.
What: /sys/class/net/<iface>/cdc_ncm/ndp_to_end
Date: Dec 2015
KernelVersion: 4.5
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Boolean attribute showing the status of the "NDP to
end" quirk. Defaults to 'N', except for devices
already known to need it enabled.
The "NDP to end" quirk makes the driver place the NDP
(the packet index table) after the payload. The NCM
specification does not mandate this, but some devices
are known to be more restrictive. Write 'Y' to this
attribute for temporary testing of a suspect device
failing to work with the default driver settings.
A device entry should be added to the driver if this
quirk is found to be required.
What: /sys/class/net/<iface>/cdc_ncm/rx_max
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
The maximum NTB size for RX. Cannot exceed the
maximum value supported by the device. Must allow at
least one max sized datagram plus headers.
The actual limits are device dependent. See
dwNtbInMaxSize.
Note: Some devices will silently ignore changes to
this value, resulting in oversized NTBs and
corresponding framing errors.
What: /sys/class/net/<iface>/cdc_ncm/tx_max
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
The maximum NTB size for TX. Cannot exceed the
maximum value supported by the device. Must allow at
least one max sized datagram plus headers.
The actual limits are device dependent. See
dwNtbOutMaxSize.
What: /sys/class/net/<iface>/cdc_ncm/tx_timer_usecs
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Datagram aggregation timeout in µs. The driver will
wait up to 3 times this timeout for more datagrams to
aggregate before transmitting an NTB frame.
Valid range: 5 to 4000000
Set to 0 to disable aggregation.
The following read-only attributes all represent fields of the
structure defined in section 6.2.1 "GetNtbParameters" of "Universal
Serial Bus Communications Class Subclass Specifications for Network
Control Model Devices" (CDC NCM), Revision 1.0 (Errata 1), November
24, 2010 from USB Implementers Forum, Inc. The descriptions are
quoted from table 6-3 of CDC NCM: "NTB Parameter Structure".
What: /sys/class/net/<iface>/cdc_ncm/bmNtbFormatsSupported
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
- Bit 0: 16-bit NTB supported (set to 1)
- Bit 1: 32-bit NTB supported
- Bits 2 – 15: reserved (reset to zero; must be ignored by host)
What: /sys/class/net/<iface>/cdc_ncm/dwNtbInMaxSize
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
IN NTB Maximum Size in bytes
What: /sys/class/net/<iface>/cdc_ncm/wNdpInDivisor
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Divisor used for IN NTB Datagram payload alignment
What: /sys/class/net/<iface>/cdc_ncm/wNdpInPayloadRemainder
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Remainder used to align input datagram payload within
the NTB: (Payload Offset) mod (wNdpInDivisor) =
wNdpInPayloadRemainder
What: /sys/class/net/<iface>/cdc_ncm/wNdpInAlignment
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
NDP alignment modulus for NTBs on the IN pipe. Shall
be a power of 2, and shall be at least 4.
What: /sys/class/net/<iface>/cdc_ncm/dwNtbOutMaxSize
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
OUT NTB Maximum Size
What: /sys/class/net/<iface>/cdc_ncm/wNdpOutDivisor
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
OUT NTB Datagram alignment modulus
What: /sys/class/net/<iface>/cdc_ncm/wNdpOutPayloadRemainder
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Remainder used to align output datagram payload
offsets within the NTB: Padding, shall be transmitted
as zero by function, and ignored by host. (Payload
Offset) mod (wNdpOutDivisor) = wNdpOutPayloadRemainder
What: /sys/class/net/<iface>/cdc_ncm/wNdpOutAlignment
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
NDP alignment modulus for use in NTBs on the OUT
pipe. Shall be a power of 2, and shall be at least 4.
What: /sys/class/net/<iface>/cdc_ncm/wNtbOutMaxDatagrams
Date: May 2014
KernelVersion: 3.16
Contact: Bjørn Mork <bjorn@mork.no>
Description:
Maximum number of datagrams that the host may pack
into a single OUT NTB. Zero means that the device
imposes no limit.
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