  Reconfigurable Intelligent Surfaces (RIS) emerge as promising technologies in
future radar and wireless communication domains. This letter addresses the
passive sensing issue utilizing wireless communication signals and RIS amidst
interference from wireless access points (APs). We introduce an atomic norm
minimization (ANM) approach to leverage spatial domain target sparsity and
estimate the direction of arrival (DOA). However, the conventional semidefinite
programming (SDP)-based solutions for the ANM problem are complex and lack
efficient realization. Consequently, we propose a RIS-ADMM method, an
innovative alternating direction method of multipliers (ADMM)-based iterative
approach. This method yields closed-form expressions and effectively suppresses
interference signals. Simulation outcomes affirm that our RIS-ADMM method
surpasses existing techniques in DOA estimation accuracy while maintaining low
computational complexity. The code for the proposed method is available online
\url{https://github.com/chenpengseu/RIS-ADMM.git}.
