docs/designs/device-tree-gpio-naming.md

12 subsystem. The replacement is a "descriptor-based" character device interface.
17 libgpiod provides a feature where you can access gpios by a name given to them
25 specific field used to name the GPIOs in the DTS is `gpio-line-names`. This
26 [patch][3] shows an example of naming the GPIOs for a system.
28 GPIOs are used for arbitrary things. It's pretty hard to have a coherent naming
29 scheme in the face of a universe of potential use-cases.
37 - Ensure common function GPIOs within OpenBMC use the same naming convention
44 for all common GPIOs.
46 This list below includes all common GPIOs within OpenBMC. Any OpenBMC system
47 which provides one of the below GPIOs must name it as listed in this document.
48 This document must be updated as new common GPIOs are added.
52 Pattern: `*-button`
55 BMC-less machines use a button to trigger system behavior and in a BMC-managed
59 #### power-button
68 - `host*-ready`: Host ready, active high
69 - `host*-ready-n`: Host ready, active low
73 - host0-ready
74 - host1-ready-n
75 - ...
79 Pattern: `led-*`
81 #### led-fault
83 #### led-identify
85 #### led-power
87 #### led-sys-boot-status
89 #### led-attention
91 #### led-hdd-fault
93 #### led-rear-fault
95 #### led-rear-power
97 #### led-rear-id
101 Pattern: `power-*`, `regulator-*`
103 #### power-chassis-control
105 Set to initiate power-on or power-off of the chassis.
107 #### power-chassis-good
111 #### power-config-full-load
122 #### power-ffs-sync-history
130 #### regulator-standby-faulted
134 non-faulted condition after AC power cycle when no standby power regulator fault
138 #### rtc-battery-voltage-read-enable
144 Pattern: `presence-*`
146 #### presence-ps0, presence-ps1, ..., presence-ps\<N>
148 ### Reset Cause
150 These are GPIOs that provide more detail on the reason for a BMC reset. BMC
152 (i.e. a BMC reset was reset by some external source). At times though, firmware
153 needs more details on the cause of a reset. Hardware can be configured to latch
156 Pattern: `reset-cause-*`
158 #### reset-cause-pinhole
160 The pinhole reset cause will be utilized by BMC firmware to know when it has
161 been reset due to a user initiated pinhole reset. This is commonly done in error
163 GPIO is not utilized to cause the actual reset, it is a GPIO that can be read
164 after the BMC reset to know the reason for the reboot was a pinhole reset.
168 #### bmc-secure-boot
180 #### air-water
184 #### factory-reset-toggle
187 has changed since the last reboot. If it has, it indicates that a factory reset
190 ### POWER Specific GPIOs
198 ##### cfam-reset
200 Utilized to issue a processor logic reset to a IBM POWER processor.
209 - Continue to hard code a config file per system type that has the gpio bank and
213 - Have the device tree GPIO names match the hardware schematics and then have
228 [2]: https://www.kernel.org/doc/html/latest/driver-api/gpio/index.html
230   https://lore.kernel.org/linux-arm-kernel/20200306170218.79698-1-geissonator@yahoo.com/