I will try to collect useful info about Linux I2C infrastructure
• wirting regmap drivers https://opensourceforu.com/2017/01/regmap‑reducing‑redundancy‑linux‑code/ 
• Using the I2C‑Stub to Emulate a Device https://eraretuya.github.io/2016/12/10/the‑i2c‑stub‑in‑action/ 
• very good overview of i2c and bus arbitration and testing https://elinux.org/images/c/c9/ELCE17‑WSang‑I2C‑Fault‑Injector.pdf 
• https://www.youtube.com/watch?v=2UU_26rlJHs