kernel_patches.md

title
Kernel Patches

Kernel Patches

• Patches get applied to "$BUILD_DIR/target-mips_34kc_uClibc-0.9.33.2/linux-ar71xx_generic/compat-wireless-2014-05-22/drivers"

• Patches modify the kernel source code at build time, and are like an "add-on" to kernel code

• Patches are of the same format as a git diff output

• Note, some of these changes are cosmetic, see commit (de3fcd38b2caecc0bc878e8bc992fe33aa23bf25)[https://github.com/UCSMA-Project/OpenWRT-14.07-JS9331/commit/de3fcd38b2caecc0bc878e8bc992fe33aa23bf25#diff-13af2413196137d2b1c0c5c56f319bd9358fc0ee620e3bbae2fea88fe8810933], with file "008-fix_netdev_unregister.patch" for example

List of patches

package/kernel/mac80211/patches

• 930-disable_11n.patch

  • Disables Wi-Fi 802.11n by setting the ht_supported (High Throughput) value to false in the "ht_info" ieee80211_sta_ht_cap structure
  • 802.11n "uses multiple antennas to increase data rates", according to (Wikipedia)[https://en.wikipedia.org/wiki/IEEE_802.11n-2009]
  • The experiement transmits using only antenna at the time, and using multiple antennas at a time isn't supported by us

• 931-bitrate_order.patch

  • See (Choose Transmitting Rate for Injected Packets)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/packet_injection_procedure.md#choose-transmitting-rate-for-injected-packets]
  • Sets desired rate in first place in ath9k_legacy_rates array since OpenWRT 14.04 doesn't let you pick the desired rate from the radiotap header
  • The bitrape is by 100 Kbps. The preferred rate is therefore set to 0x18 * 100 Kbps = 2.4 Mbps

• 932-add_nf_2g_info_to_debugfs_misc.patch

  • Prints NF 2G debug information when read_file_misc is called in "debug.c"
  • Noise Floor information for the 2.4 GHz channel: minimum, maximum and nominal
    • Noise floor: a higher noise floor means less sensitivity to noise / interferences around the router
    • Nominal: default value
    • Max / min: range of allowed noise floor values

• 933-add_hardware_queue_details_to_debugfs_queues.patch

  • Prints extra transmission queue information when print_queue is called "debug.c".
    • Hardware queue number (ath9k has 10 queues)
    • Hardware queue depth
    • Hardware A-MPDU
      • Aggregation of 802.11 frames, also called MAC Protocol Data Unit
    • Pending frames in the TX queue
    • Whether the TX queue is stopped
    • TX queue Contention Window min and max: range of values to use when backing off on collision
    • TX queue Arbitration Inter-Frame Spacing (AIFS): the amount of time to wait between a request frame in μs. See (Arbitration Inter-Frame Spacing (AIFS))[https://www.tutorialspoint.com/arbitration-inter-frame-spacing-aifs]
    • TX queue Burst Time: maximum amount of time during which frames can be transmitted at once. Packets in the same burst share the same 802.11 header
  • NOTE: a TX queue has a axq_num ATH9K hardware queue number, used to access the information from the TX queue
  • NOTE: sc is the software context of the driver

• 934-allow_modification_of_txq_params_in_mesh_and_monitor_mode.patch

  • Commit (a8581cca7318a09b788754bb2b7ae651e8ecfcba)[https://github.com/UCSMA-Project/OpenWRT-14.07-JS9331/blob/master/package/kernel/mac80211/patches/934-allow_modification_of_txq_params_in_mesh_and_monitor_mode.patch]
  • See (Improve Support for Pure Monitor Mode)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/packet_injection_procedure.md#improve-support-for-pure-monitor-mode] on the need to modify TX queue parameters
  • Modifies the nl80211 interface to allow setting parameters when the device is in mesh mode or monitor mode
  • Note: "wiphy" refers to a physical device

• 935-export_ath_hw_in_init.patch

  • Exports the ath_hw ath9k hardware abstract data structure, making it available to other kernel modules
  • Allows the kernel unlocking module to read and write hardware registers of the card
  • See (Unlocking Kernel Module)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/implement_unlocking.md]

• 936-disable_tx_hung_reset.patch

  • For ath_tx_complete_poll_work in link.c
  • Disables resetting TX queue resets by returning early
  • Normally, the axq_tx_inprogress flag is set on a TX queue, and unset in ath_tx_process_buffer in xmit.c when transmitting
  • If ath_tx_complete_poll_work is called again and the flag is set, the TX queue is reset
  • When backing off after a collision, the TX queue could be considered "hung"
    • This patch avoids unnecessarily resetting the queue

• 937-disable_beacon_stuck_reset

  • Noise floor calibration occurs either periodically, or when the beacon is considered stuck, see (ATH9K Calibration Process)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/creating_experimental_topology.md#ath9k-calibration-process]
  • For ath9k_beacon_tasklet in beacon.c, prevents the TX queue from being reset, and the beacon from being considered stuck
  • Note that we want the Noise Floor settings to stay constant to avoid interferences between routers

• 938-set_maxCCApwr.patch

  • See (Load Noise Floor into Hardware)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/creating_experimental_topology.md#load-noise-floor-into-hardware]
  • In ath9k_hw_loadnf, sets initial and max NF for calibration
  • Note: this patch is overwritten by "957-make_nfcal_parameter_adjustable_through_debugfs.patch"

• 939-add_bf_pushback_counter.patch

  • Adds a "bfpushback" counter to TX queues
  • "bfpushback" is incremented in ath_tx_edma_tasklet when a TX buffer is stale
    • Note: eDMA = Enhanced Direct Memory Access
  • "bfpushback" is printed when read_file_xmit is called

• 940-ensure_only_one_MPDU_or_AMPDU_in_hw_queue.patch

  • Commit (fc7aa359602ffeeca64fced72232e773d2334e9e)[https://github.com/UCSMA-Project/OpenWRT-14.07-JS9331/commit/fc7aa359602ffeeca64fced72232e773d2334e9e]
  • Reduces TXFIFO queue to 1 frame, and only allows 1 frame at a time in the TXFIFO queue
    • Modifies the ATH_TXFIFO_DEPTH macro to 1
  • Used to more quickly interrupt transmission on collision
  • See (Modified Driver Code)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/TX_path_analysis.md#modified-driver-code]

• 941-add_timer_to_record_last_hw_puttxbuf_call.patch

  • Keeps track of when packets were put in a TX buffer
  • Adds in the ath_hw struct a last_puttxbuf timeval, recorded when ath9k_hw_puttxbuf is called
  • In ath_tx_edma_tasklet, prints the time since a packet was last put in the TX buffer if the debug flag / mask is set in the ath_common struct

• 943-add_param_for_force_quiet_bit_after_puttxbuf.patch

  • The quiet bit makes the router think there is a collision, and wait to transmit again
  • Creates a force_quiet_bit_delay flag in the ath_hw struct
    • If the flag is set, AR_PCU_FORCE_QUIET_COLL is set when ath9k_hw_puttxbuf is called
  • Forcing this quiet bit after each transmission ("puttxbuf") delays ath9k_hw_puttxbuf from executing again
  • See (Modified ath9k TX path)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/TX_path_analysis.md#modified-ath9k-tx-path]

• 943-add_switch_to_force_quiet_bit.patch

  • Only unsets AR_PCU_FORCE_QUIET_COLL in ath9k_hw_puttxbuf if force_quiet_bit_restore is set in the ath_hw struct
  • Extends "942-add_param_for_force_quiet_bit_after_puttxbuf.patch"

• 944-add_another_timer_after_interrupt_tx.patch

  • Extends "941-add_timer_to_record_last_hw_puttxbuf_call.patch"
  • Keeps track of when AR_PCU_FORCE_QUIET_COLL was last unset, and prints that time in ath_tx_edma_tasklet

• 945-add_param_to_control_delay_between_set_clear_the_force_quiet_bit.patch

  • Adds a parameter in μs to control the time to wait in ath9k_hw_puttxbuf before unsetting the quiet collision bit
  • See "943-add_param_for_force_quiet_bit_after_puttxbuf.patch" for when the quiet bit is set

• 946-switch_to_getnstimeofday.patch

  • Replaces do_gettimeofday by getnstimeofday
  • getnstimeofday is faster and more precise

• 947-add_batch_logging.patch

  • Adds a current_timing_count and max_timing_count to the ath_hw struct
  • If current_timing_count >= max_timing_count, prints the time difference between now and the current_timing_count records of last_puttxbuf and last_interrupt_tx
  • Every time a last_puttxbuf is recorded, the current_timing_count is incremented
  • last_puttxbuf values are recorded in ath9k_hw_puttxbuf, and last_interrupt_tx is only recorded in ath9k_hw_puttxbuf if force_quiet_bit_delay and force_quiet_bit_restore are set in the ath_hw struct

• 948-allow_zero_cwmin_cwmax.patch

  • Allows the min and max Contention Window (CW) to be 0
    • Contention Window: the amount of time to wait before retransmitting after a collision occurs

• 949-optional_eifs_equal_to_aifs.patch

  • Adds a eifs_equal_to_aifs parameter in the ath_hw struct that sets the EIFS time to the AIFS time if set to the true
  • Extended Inter Frame Spacing (EIFS) and Arbitrary Inter Frame Spacing (AIFS) are backoff times, and EIFS is longer by default
  • If a wireless adapter detects a 802.11 wireless signal but fails to decode the content of that frame, the adapter switches to EIFS
    • This avoids issues with a middle node competing for transmissino channels
  • See (Add option to disable EIFS (Extended Inter Frame Spacing))[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/packet_injection_procedure.md#add-option-to-disable-eifs-extended-inter-frame-spacing]

• 950-re_structure_delay_logging_code.patch

  • Changes the default max_timing_count of ath_hw to 1 when initialized in ath9k_init_softc
  • Cleans up the logic to log quiet collisions in ath9k_hw_puttxbuf and ath_tx_edma_tasklet
  • Modifies quiet collision attributes in ath_hw struct
    • last_puttxbuf is now and single element, not an array
    • Adds last_interrupt_tx, puttxbuf_delay, force_quiet_restore_delay and since_last_txok timespec array attributes
    • Adds last_force_quiet_restore and last_txok_irq timespec attributes

• 951-fix_mis_type_in_debug_code.patch

  • Fix wrong type use in function parameters for write_force_quiet_bit_restore, write_max_timing_count and write_eifs_equal_to_aifs
    • char __user *user_buf -> const char __user *user_buf

• 952-add_log_for_unlocking.patch

  • Adds unlocking_logging and unlocked attributes to the ath_hw struct
  • In ath_tx_edma_tasklet, only logs unlocking, or restoring the quiet bit after a transmission / collision if unlocking_logging is false or if unlocking_logging and unlocked are true
  • TODO

• 953-add_driver_gpio_out.patch

  • Adds a GPIO output to indicate if a transmission is in progress
    • Sends a pulse when the TX_OK interrupt is handled
    • Allows a monitoring device to record when interruptions happen
  • GPIO pulse is set when ath9k_hw_puttxbuf is called
  • ath_tx_edma_tasklet keeps the GPIO unset while starting its loop
  • See (TX Monitoring Architecture)[https://github.com/UCSMA-Project/unpublished-docs/blob/master/UCSMA_monitor_node.md#tx-monitoring-architecture]

• 954-allow_iw_set_wmm_params_for_monitor_interface.patch

  • Further tweak of "300-add_txq_control.patch"
  • Allows setting TX queue CW, AIFS and Burst Time with iw even if an interface is in monitor mode
  • See (Config Contention Window/AIFS/Burst Duration)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/AR9331_set_parameters.md#config-contention-windowaifsburst-duration]

• 955-allow_set_tx_power_for_monitor_interface.patch

  • Allows adjusting the transmission power even if the wireless adapter only has 1 monitor mode interface
  • In __ieee80211_recalc_txpower sets the transmission power to the user_power_level in the ieee80211_sub_if_data struct
  • In ieee80211_hw_conf_chan, allows a monitor mode interface (NL80211_IFTYPE_MONITOR) to have its transmission power level set
  • See (Improve Support for Pure Monitor Mode)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/packet_injection_procedure.md#improve-support-for-pure-monitor-mode]

• 956-enable_channel_14.patch

  • Sets the regulatory domain to Japan to enable the Wi-Fi channel 14
  • Aims to reduce interferences in the testing environment since this channel is less used
  • Note: this should probably note be used outside of a testing environment as this channel is not "permitted" in North America (see (WirelesSHack)[https://www.wirelesshack.org/router-channel-14-the-banned-channel.html])
    • It's also a bit dodgy to be modifying the regulatory domain

• 957-make_nfcal_parameter_adjustable_through_debugfs.patch

  • See (Load Noise Floor into Hardware)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/creating_experimental_topology.md#load-noise-floor-into-hardware]
  • In ath9k_hw_loadnf, sets initial and max NF for calibration
  • Also modifies AR_PHY_CCA_MAX_GOOD_VAL_9300_2GHZ from -60 to -95
  • Note: this patch overwrites "938-set_maxCCApwr.patch"

• 958-add_noise_floor_override_option.patch

  • Backport of the (ath9k: add noise floor override option)[https://patchwork.kernel.org/project/linux-wireless/patch/20170316151337.24163-4-sw@simonwunderlich.de/] OWRT patch
  • Allows overriding automatically calibrated noise floor with the following command: echo [${noise_floor}] > /sys/kernel/debug/ieee80211/phy0/ath9k/nf_override
  • See (Config Noise Floor)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/AR9331_set_parameters.md#config-noise-floor
  • See (Load Noise Floor into Hardware)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/creating_experimental_topology.md#load-noise-floor-into-hardware] for an explanation of why the default noise floor calibration can adversely affect our mesh network

• 959-use_long_slot_when_init_hw.patch

  • Slot time = contention window = amount of time to wait to retransmit after a collision
  • Sets the ath_hw struct's slottime to 20μs by default instead of 9μs, in ath9k_hw_init_defaults

Other patches

• package/network/utils/iw/patches/300-add_txq_control.patch

  • Modifies iw to set be able to set TX queues Contention Windows, AIFS, and Burst Time
  • See (Config Contention Window/AIFS/Burst Duration)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/AR9331_set_parameters.md#config-contention-windowaifsburst-duration]

• target/linux/generic/patches-3.10/728-MIPS-ath79-add-gpio-irq.patch

  • Backported patch from OpenWRT 15 to allow GCC 6 to compile toolchain, from commit 42e95284abe4c1873960aca402339ab1ef5a1b8f toolchain/gcc/patches/4.8-linaro/030-gcc-6-compile.patch

Trivially changed patches

• These appear when running git diff --name-only against the last not made by us. They are listed here for your information

• Note, these changes showed up from this commit merging upstream changes: (de3fcd38b2caecc0bc878e8bc992fe33aa23bf25)[https://github.com/UCSMA-Project/OpenWRT-14.07-JS9331/commit/de3fcd38b2caecc0bc878e8bc992fe33aa23bf25]

• All patches occur in "package/kernel/mac80211/patches"

• 008-fix_netdev_unregister.patch

• 150-disable_addr_notifier.patch

• 300-pending_work.patch

• 402-ath9k-fix-invalid-mac-address-handling.patch

• 411-ath5k_allow_adhoc_and_ap.patch

• 431-add_platform_eeprom_support_to_ath5k.patch

• 440-ath5k_channel_bw_debugfs.patch

• 510-ath9k_intr_mitigation_tweak.patch

• 522-mac80211_configure_antenna_gain.patch

  • (FYI) A patch by OpenWRT originally to allow users to set the maximum to reduce the transmission power

• 530-ath9k_extra_leds.patch

• 541-ath9k_rx_dma_stop_check.patch

• 550-ath9k_entropy_from_adc.patch

• 565-ath9k_restart_after_nfcal_failure.patch

• 600-0003-rt2x00-rt2800-serialize-shared-memory-access.patch

• 600-0005-rt2x00-rt2800lib-add-hw_beacon_count-field-to-struct.patch

• 600-0006-rt2x00-rt2800lib-init-additional-beacon-offset-regis.patch

• 600-0014-rt2x00-rt2800lib-add-MAC-register-initialization-for.patch

• 600-0016-rt2x00-rt2800lib-add-BBP-register-initialization-for.patch

• 600-0020-rt2x00-rt2800lib-add-channel-configuration-code-for-.patch

  • Here, these changes are not whitespace only, but are just the result of an upstream merge, as evidenced by their presence in other forked repositories, such as (here)[https://gitlab.nic.cz/turris/openwrt/-/blob/deploy-2015-12-18/package/kernel/mac80211/patches/600-0020-rt2x00-rt2800lib-add-channel-configuration-code-for-.patch#L129]

• 600-0029-rt2x00-rt2800lib-fix-VGC-setup-for-RT3883.patch

• 616-rt2x00-support-rt5350.patch

• 800-b43-backports-form-wireless-testing-master-master-20.patch

• 910-01-add-support-for-mt7620.patch

Other changes

• In "include/kernel-defaults.mk", the version magic is fixed to work with kmod

  • NOTE: If another version of OpenWRT were used, this value would need to be changed

• rules.mk

  • Whitespace

• scripts/download.pl

  • New mirrors

• target/linux/ar71xx/base-files/etc/uci-defaults/10_js9331

  • Handlers added, probably to configure buttons on board to do something, like rebooting

• target/linux/ar71xx/files/arch/mips/ath79/mach-tl-wr720n-v3.c

  • Configure GPIO, buttons and LEDs on board

Helper scripts

• In the "helper_scripts" directory
• rget and rset let you get and set register values on ath9k registers
• See (Read/Write Registers)[https://github.com/UCSMA-Project/unpublished-docs/blob/f7b42e12a9afcb3f788b5bfbffe54fa069ad6e51/AR9331_set_parameters.md#readwrite-registers]

TODOs

• Remove patch 938 since it is overwritten by 957
  • NOTE: this would involve modifying patch 957 so that the (-) diff corresponds to the original code
• Merge path 951 into other patches since it just fixes bugs introduced in previous patches (943, 947, 949)