Re: [PATCH v15 02/15] irqdomain: Add IRQ_DOMAIN_FLAG_MSI_IMMUTABLE and irq_domain_is_msi_immutable()

On Tue, 11 Feb 2025 19:21:55 +0000, Frank Li Frank.Li@nxp.com wrote:

Add the flag IRQ_DOMAIN_FLAG_MSI_IMMUTABLE and the API function irq_domain_is_msi_immutable() to check if the MSI controller retains an immutable address/data pair during irq_set_affinity().

Ensure compatibility with MSI users like PCIe Endpoint Doorbell, which require the address/data pair to remain unchanged after setup. Use this function to verify if the MSI controller is immutable.

Why is that a requirement? Why should a driver even care?

M.