TWI / I2C Development and Testing

Confirm the actual T527 bus numbering first

find bsp device kernel -type f \( -name '*.dts' -o -name '*.dtsi' \) -print0   | xargs -0 grep -n 'twi0:\|i2c@'
grep -Rni 'CONFIG_.*TWI\|CONFIG_.*I2C' bsp device kernel

Target checks:

i2cdetect -l
i2cdetect -y 0
i2cget -y 0 0x50 0x00
i2cset -y 0 0x50 0x00 0x12
i2cdump -y 0 0x50
i2ctransfer -y 0 w1@0x50 0x00 r1

An i2cdetect scan can change device state. Confirm that PMIC, camera, touch, and other sensitive devices can be scanned safely.

Userspace interface

With the I2C device interface enabled, access /dev/i2c-X through open(), ioctl(I2C_SLAVE_FORCE), read(), and write(). Use I2C_RDWR or i2ctransfer for repeated-start transactions; separate write/read calls can break the required bus sequence.

Slave mode

Slave mode requires both the controller support and a slave client driver with the matching DTS child node. Validate it with another controller or an external master while observing interrupts, receive buffers, and ACK behavior.

Common build and flash workflow

cd <ANDROID_TOP>/longan
./build.sh kernel
./build.sh pack

After flashing, confirm the kernel/DTB build timestamp and version so that new changes are not evaluated on an old image.