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authorBjørn Mork <bjorn@mork.no>2014-05-30 09:31:10 +0200
committerDavid S. Miller <davem@davemloft.net>2014-06-02 16:01:31 -0700
commite3cfeefc0e491af00155525131285821e26f7715 (patch)
treebeb0140b21a7ff9e3dca3889f7d36f3ab718b29c /Documentation
parent39eb7e0e8c88dee58f83df8aa9f7a58559fa45ee (diff)
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net: cdc_ncm: document the sysfs API
Adding documentation for all the driver specific sysfs attributes. Cc: Peter Stuge <peter@stuge.se> Signed-off-by: Bjørn Mork <bjorn@mork.no> Signed-off-by: David S. Miller <davem@davemloft.net>
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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/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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