[tip: irq/core] genirq/msi: Provide msi_domain_ops:: Prepare_desc()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     8f986fd7755bec8b8c5776824afa1bd1151986d9
Gitweb:        https://git.kernel.org/tip/8f986fd7755bec8b8c5776824afa1bd1151986d9
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Fri, 25 Nov 2022 00:26:16 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 05 Dec 2022 22:22:33 +01:00

genirq/msi: Provide msi_domain_ops:: Prepare_desc()

The existing MSI domain ops msi_prepare() and set_desc() turned out to be
unsuitable for implementing IMS support.

msi_prepare() does not operate on the MSI descriptors. set_desc() lacks
an irq_domain pointer and has a completely different purpose.

Introduce a prepare_desc() op which allows IMS implementations to amend an
MSI descriptor which was allocated by the core code, e.g. by adjusting the
iomem base or adding some data based on the allocated index. This is way
better than requiring that all IMS domain implementations preallocate the
MSI descriptor and then allocate the interrupt.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221124232326.444560717@xxxxxxxxxxxxx

---
 include/linux/msi.h | 6 +++++-
 kernel/irq/msi.c    | 3 +++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index dca3b80..cb0bee3 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -410,6 +410,8 @@ struct msi_domain_info;
  * @msi_init:		Domain specific init function for MSI interrupts
  * @msi_free:		Domain specific function to free a MSI interrupts
  * @msi_prepare:	Prepare the allocation of the interrupts in the domain
+ * @prepare_desc:	Optional function to prepare the allocated MSI descriptor
+ *			in the domain
  * @set_desc:		Set the msi descriptor for an interrupt
  * @domain_alloc_irqs:	Optional function to override the default allocation
  *			function.
@@ -421,7 +423,7 @@ struct msi_domain_info;
  * @get_hwirq, @msi_init and @msi_free are callbacks used by the underlying
  * irqdomain.
  *
- * @msi_check, @msi_prepare and @set_desc are callbacks used by the
+ * @msi_check, @msi_prepare, @prepare_desc and @set_desc are callbacks used by the
  * msi_domain_alloc/free_irqs*() variants.
  *
  * @domain_alloc_irqs, @domain_free_irqs can be used to override the
@@ -444,6 +446,8 @@ struct msi_domain_ops {
 	int		(*msi_prepare)(struct irq_domain *domain,
 				       struct device *dev, int nvec,
 				       msi_alloc_info_t *arg);
+	void		(*prepare_desc)(struct irq_domain *domain, msi_alloc_info_t *arg,
+					struct msi_desc *desc);
 	void		(*set_desc)(msi_alloc_info_t *arg,
 				    struct msi_desc *desc);
 	int		(*domain_alloc_irqs)(struct irq_domain *domain,
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 0749e66..6370ea5 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -1254,6 +1254,9 @@ static int __msi_domain_alloc_irqs(struct device *dev, struct irq_domain *domain
 		if (WARN_ON_ONCE(allocated >= ctrl->nirqs))
 			return -EINVAL;
 
+		if (ops->prepare_desc)
+			ops->prepare_desc(domain, &arg, desc);
+
 		ops->set_desc(&arg, desc);
 
 		virq = __irq_domain_alloc_irqs(domain, -1, desc->nvec_used,