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Commit e3cfeefc authored by Bjørn Mork's avatar Bjørn Mork Committed by David S. Miller
Browse files

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: default avatarBjørn Mork <bjorn@mork.no>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 39eb7e0e

Documentation/ABI/testing/sysfs-class-net-cdc_ncm

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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.