linux-kernel - [PATCH v2 1/5] genirq/msi: Add .msi_teardown() callback as the reverse of .msi

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Message-Id: <20250513163144.2215824-2-maz@kernel.org>
Date: Tue, 13 May 2025 17:31:40 +0100
From: Marc Zyngier <maz@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Sascha Bischoff <sascha.bischoff@....com>,
	Timothy Hayes <timothy.hayes@....com>
Subject: [PATCH v2 1/5] genirq/msi: Add .msi_teardown() callback as the reverse of .msi_prepare()

While the MSI ops do have a .msi_prepare() callback that is
responsible for setting up the relevant (usually per-device)
allocation, there is no callback reversing this setup.

For this purpose, add .msi_teardown() callback.

In order to avoid breaking the ITS driver that suffers from related
issues, do not call the call back just yet.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 include/linux/msi.h | 10 ++++++++--
 kernel/irq/msi.c    |  8 ++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 8c0ec9fc05a39..63c23003ec9b7 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -423,6 +423,7 @@ 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
+ * @msi_teardown:	Reverse the effects of @msi_prepare
  * @prepare_desc:	Optional function to prepare the allocated MSI descriptor
  *			in the domain
  * @set_desc:		Set the msi descriptor for an interrupt
@@ -438,8 +439,9 @@ struct msi_domain_info;
  * @get_hwirq, @msi_init and @msi_free are callbacks used by the underlying
  * irqdomain.
  *
- * @msi_check, @msi_prepare, @prepare_desc and @set_desc are callbacks used by the
- * msi_domain_alloc/free_irqs*() variants.
+ * @msi_check, @msi_prepare, @msi_teardown, @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
  * default allocation/free functions (__msi_domain_alloc/free_irqs). This
@@ -461,6 +463,8 @@ struct msi_domain_ops {
 	int		(*msi_prepare)(struct irq_domain *domain,
 				       struct device *dev, int nvec,
 				       msi_alloc_info_t *arg);
+	void		(*msi_teardown)(struct irq_domain *domain,
+					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,
@@ -489,6 +493,7 @@ struct msi_domain_ops {
  * @handler:		Optional: associated interrupt flow handler
  * @handler_data:	Optional: associated interrupt flow handler data
  * @handler_name:	Optional: associated interrupt flow handler name
+ * @alloc_data:		Optional: associated interrupt allocation data
  * @data:		Optional: domain specific data
  */
 struct msi_domain_info {
@@ -501,6 +506,7 @@ struct msi_domain_info {
 	irq_flow_handler_t		handler;
 	void				*handler_data;
 	const char			*handler_name;
+	msi_alloc_info_t		*alloc_data;
 	void				*data;
 };
 
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 2b3ef2333dbc8..a3b34c3c599be 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -795,6 +795,11 @@ static int msi_domain_ops_prepare(struct irq_domain *domain, struct device *dev,
 	return 0;
 }
 
+static void msi_domain_ops_teardown(struct irq_domain *domain,
+				    msi_alloc_info_t *arg)
+{
+}
+
 static void msi_domain_ops_set_desc(msi_alloc_info_t *arg,
 				    struct msi_desc *desc)
 {
@@ -820,6 +825,7 @@ static struct msi_domain_ops msi_domain_ops_default = {
 	.get_hwirq		= msi_domain_ops_get_hwirq,
 	.msi_init		= msi_domain_ops_init,
 	.msi_prepare		= msi_domain_ops_prepare,
+	.msi_teardown		= msi_domain_ops_teardown,
 	.set_desc		= msi_domain_ops_set_desc,
 };
 
@@ -841,6 +847,8 @@ static void msi_domain_update_dom_ops(struct msi_domain_info *info)
 		ops->msi_init = msi_domain_ops_default.msi_init;
 	if (ops->msi_prepare == NULL)
 		ops->msi_prepare = msi_domain_ops_default.msi_prepare;
+	if (ops->msi_teardown == NULL)
+		ops->msi_teardown = msi_domain_ops_default.msi_teardown;
 	if (ops->set_desc == NULL)
 		ops->set_desc = msi_domain_ops_default.set_desc;
 }
-- 
2.39.2