from
/usr/src/linux/drivers/net/wireless/hermes.c

static int hermes_issue_cmd(hermes_t *hw, u16 cmd, u16 param0)
{
	int k = CMD_BUSY_TIMEOUT;
	u16 reg;

	/* First wait for the command register to unbusy */
	reg = hermes_read_regn(hw, CMD);
	while ( (reg & HERMES_CMD_BUSY) && k ) {
		k--;
		udelay(1);
		reg = hermes_read_regn(hw, CMD);
	}
	DEBUG(3, "hermes_issue_cmd: did %d retries.\n", CMD_BUSY_TIMEOUT-k);
	if (reg & HERMES_CMD_BUSY) {
		return -EBUSY;
	}

	hermes_write_regn(hw, PARAM2, 0);
	hermes_write_regn(hw, PARAM1, 0);
	hermes_write_regn(hw, PARAM0, param0);
	hermes_write_regn(hw, CMD, cmd);
	
	return 0;
}