> +	switch (event) {
> +	case I2C_SLAVE_STOP:
> +		command_size = panel->idx;
> +		fallthrough;
> +	case I2C_SLAVE_WRITE_REQUESTED:
> +		panel->idx = 0;
> +		break;
> +	case I2C_SLAVE_WRITE_RECEIVED:
> +		if (panel->idx < sizeof(panel->command))
> +			panel->command[panel->idx++] = *val;
> +		else
> +			dev_dbg(&panel->input->dev, "command truncated\n");

Just double checking: Do you really want to process truncated commands?
Since you detect the state here, you could also choose to reject such
commands?