[PATCH 1/2] genirq/msi, platform-msi: Adjust return value of msi_domain_prepare_irqs()

[Huacai Chen <chenhuacai@loongson.cn>]

Adjust the return value semanteme of msi_domain_prepare_irqs(), which
allows us to modify the input nvec by overriding the msi_domain_ops::
msi_prepare(). This is necessary for the later patch.

Before:
0 on success, others on error.

After:
= 0: Success;
> 0: The modified nvec;
< 0: Error code.

Callers are also updated.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/base/platform-msi.c |  2 +-
 kernel/irq/msi.c            | 10 +++++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/base/platform-msi.c b/drivers/base/platform-msi.c
index f37ad34c80ec..e4a517c144e7 100644
--- a/drivers/base/platform-msi.c
+++ b/drivers/base/platform-msi.c
@@ -298,7 +298,7 @@ __platform_msi_create_device_domain(struct device *dev,
 
 	platform_msi_set_proxy_dev(&data->arg);
 	err = msi_domain_prepare_irqs(domain->parent, dev, nvec, &data->arg);
-	if (err)
+	if (err < 0)
 		goto free_domain;
 
 	return domain;
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 7a97bcb086bf..d151936aec05 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -1058,6 +1058,12 @@ bool msi_match_device_irq_domain(struct device *dev, unsigned int domid,
 	return ret;
 }
 
+/*
+ * Return Val:
+ * = 0: Success;
+ * > 0: The modified nvec;
+ * < 0: Error code.
+ */
 int msi_domain_prepare_irqs(struct irq_domain *domain, struct device *dev,
 			    int nvec, msi_alloc_info_t *arg)
 {
@@ -1260,8 +1266,10 @@ static int __msi_domain_alloc_irqs(struct device *dev, struct irq_domain *domain
 	int i, ret, virq;
 
 	ret = msi_domain_prepare_irqs(domain, dev, ctrl->nirqs, &arg);
-	if (ret)
+	if (ret < 0)
 		return ret;
+	if (ret > 0)
+		ctrl->nirqs = ret;
 
 	/*
 	 * This flag is set by the PCI layer as we need to activate
-- 
2.39.1