  We propose a unified and deterministic scheme to generate arbitrary
single-photon multimode $W$ states in circuit QED. A three-level system
(qutrit) is driven by a pump-laser pulse and coupled to $N$ spatially separated
resonators. The coupling strength for each spatial mode $g_i$ totally decide
the generated single-photon N-mode $W$ state $\vert W_N
\rangle=\frac{1}{A}\sum_{i=1}^N g_i|0_1 0_2 \cdots 1_i 0_{i+1}\cdots
0_N\rangle$, so arbitrary $\vert W_N \rangle$ can be generated just by tuning
$g_i$. We could not only generate $W$ states inside resonators but also release
them into transmission lines on demand. The time and fidelity for generating
(or emitting) $\vert W_N \rangle$ can both be the same for arbitrary $N$.
Remarkably, $\vert W_N\rangle$ can be emitted with probability reaching
$98.9\%$ in $20-50$ ns depending on parameters, comparable to the recently
reported fastest two-qubit gate ($30-45$ ns). Finally, the time evolution
process is convenient to control since only the pump pulse is time-dependent.
