The kernel drivers in this repository are mostly running on a 4.19 kernel. They should be backward compatible to 4.9 and potentially compatible with higher kernel version like 5.10.
The scd-hwmon is a central kernel module on Arista devices and gets loaded on
all platforms.
When this driver is loaded, the various gpios and resets are exposed on the sysfs.
They can be set and unset by writing into the sysfs file.
The meaning of 0 or 1 should be deduced based on the name of the sysfs entry.
cd /sys/module/scd/drivers/pci:scd/<pciAddr>/
# put the switch chip in reset
echo 1 > switch_chip_reset
This section describes how to interact with the various components exposed by the kernel drivers. In order to see them, the platform must be successfully initialized.
The following sections describe how to manually interact with the components. Examples shown may differ across platforms but the logic stays the same.
LED objects can be found under /sys/class/leds.The brightness field is used to
toggle between off and different colors.
The brightness to LED color mapping is as follows (0 maps to off for all LEDs):
status, fan_status, psu1, psu2:
0 => off
1 => green
2 => red
beacon:
1+ => blue
qsfp:
1 => green
2 => amber
fan:
1 => green
2 => red
3 => amber
Given that this repository is primarily aimed at running on SONiC, an
implementation of the led_control plugin is available under
arista.utils.sonic_leds. It requires access to the port_config.ini file to
translate from interface name to front panel port.
Fans are exposed under /sys/class/hwmon/* and respect the
sysfs-interface
guidelines.
This repository provides the kernel modules to handle the fans.
Temperature sensors are exposed under /sys/class/hwmon/* and also respect
the sysfs-interface.
They are all managed by linux standard modules like lm73 and max6658.
Power supplies and power controllers can be managed by the kernel's
generic pmbus module. Assuming the pmbus module was compiled into the
kernel.
Some power supplies may need kernel patches against the pmbus driver.
The system eeprom contains platform specific information like the SKU, the
serial number and the base mac address.
The location of the eeprom that contains this information vary from one product to
another. The most reliable way to get this information is to run arista syseeprom
The library implements the SONiC eeprom plugin under arista.utils.sonic_eeprom.
Currently only platforms with QSFP+, SFP+, OSFP and QSFP-DD ports are supported. All transceivers provide 2 kinds of information.
The first piece of information is obtained from the transceiver physical pins.
- OSFP: present, reset, low power mode, interrupt, module select
- QSFP: present, reset, low power mode, interrupt, module select
- SFP: present, rxlos, txfault, txdisable
These knobs are accessible under /sys/module/scd/drivers/pci:scd/.../
The name of the entries follow this naming <type><id>_<pin>
For example qsfp2_reset or sfp66_txdisable.
See this section on how to use them.
The second piece of information provided by a transceiver is the content of its
eeprom. It is accessible via SMBus at the fixed address 0x50. Some
transceivers also exist at other SMBus addresses like 0x51 and 0x56.
On linux, an unoffical module called optoe manages such devices.
This library implements the spfutil plugin for SONiC to manage xcvrs.
Before being read, the QSFP+, OSFP and QSFP-DD modules must be taken out of reset and have their module select signals asserted. This can be done through the GPIO interface. The library does it at boot time.
On the DCS-7050QX-32S, the first QSFP port and the 4 SFP ports are multiplexed.
To choose between one or the other, write into the sysfs file located under
/sys/modules/scd/drivers/pci:scd/.../mux_sfp_qsfp
Most of the GPIOs of the system are exposed by the scd-hwmon driver.
They should be available under /sys/module/scd/drivers/pci:scd/.../.