I've tried images before and after PR #912. It appears that this PR broke sonic on Arista-7260CX3-64 platform. Not sure if any other Arista/Broadcom platform would encounter this same issue.

The issue seemingly related to syncd unable to discover the Broadcom device on PCI bus. Though lspci shows them:

admin@str-7260cx3-acs-1:/var/log$ lspci | grep Broadcom
01:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM57762 Gigabit Ethernet PCIe (rev 20)
02:00.0 Ethernet controller: Broadcom Corporation NetXtreme BCM57762 Gigabit Ethernet PCIe (rev 20)
07:00.0 Ethernet controller: Broadcom Corporation Device b970 (rev 01)
07:00.1 Ethernet controller: Broadcom Corporation Device b970 (rev 01)
syslog snipet:

Aug 25 16:43:38.0 str-7260cx3-acs-1 INFO supervisord: syncd Error : Unknow bus type 0x0 !!#15
Aug 25 16:43:38.0 str-7260cx3-acs-1 INFO supervisord: syncd #15#015
Aug 25 16:43:38.0 str-7260cx3-acs-1 INFO supervisord: syncd Initializing platform#015#015
Aug 25 16:43:38.0 str-7260cx3-acs-1 INFO supervisord: syncd Boot flags: Cold boot#015
Aug 25 16:43:38.0 str-7260cx3-acs-1 INFO supervisord: syncd No attached units.#15
Aug 25 16:43:38.0 str-7260cx3-acs-1 CRIT syncd: brcm_sai_initialize_switch:208 hw info get failed with error Invalid unit (0xfffffffd).
Aug 25 16:43:38.0 str-7260cx3-acs-1 NOTICE syncd: :- main: finished initializing ASIC
Aug 25 16:43:38.0 str-7260cx3-acs-1 ERR syncd: :- main: fail to sai_initialize_switch: -1