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

[Frank Li <Frank.Li@nxp.com>]

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.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change from v14 to v15
- none

change from v13 to v14
- Roll back to v12 version because Marc Zyngier have concern about add
DOMAIN_BUS_DEVICE_PCI_EP_MSI.
https://lore.kernel.org/imx/861pxfq315.wl-maz@kernel.org/

Change from v11 to v12
- change to IRQ_DOMAIN_FLAG_MSI_IMMUTABLE to minimized the code change.
---
 include/linux/irqdomain.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index e432b6a12a32f..3dbe05d8740e6 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -231,6 +231,9 @@ enum {
 	/* Irq domain must destroy generic chips when removed */
 	IRQ_DOMAIN_FLAG_DESTROY_GC	= (1 << 10),
 
+	/* Address and data pair is mutable when irq_set_affinity() */
+	IRQ_DOMAIN_FLAG_MSI_IMMUTABLE	= (1 << 11),
+
 	/*
 	 * Flags starting from IRQ_DOMAIN_FLAG_NONCORE are reserved
 	 * for implementation specific purposes and ignored by the
@@ -692,6 +695,10 @@ static inline bool irq_domain_is_msi_device(struct irq_domain *domain)
 	return domain->flags & IRQ_DOMAIN_FLAG_MSI_DEVICE;
 }
 
+static inline bool irq_domain_is_msi_immutable(struct irq_domain *domain)
+{
+	return domain->flags & IRQ_DOMAIN_FLAG_MSI_IMMUTABLE;
+}
 #else	/* CONFIG_IRQ_DOMAIN_HIERARCHY */
 static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
 			unsigned int nr_irqs, int node, void *arg)

-- 
2.34.1