[tip: irq/msi] genirq/msi: Add abuse prevention comment to msi header

[tip-bot2 for Thomas Gleixner]

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

Commit-ID:     ef3350c53d2aac65cf1c4ecc968bbb1de5f421ea
Gitweb:        https://git.kernel.org/tip/ef3350c53d2aac65cf1c4ecc968bbb1de5f421ea
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Mon, 06 Dec 2021 23:51:49 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 16 Dec 2021 22:22:20 +01:00

genirq/msi: Add abuse prevention comment to msi header

Hope dies last.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211206210749.170847844@xxxxxxxxxxxxx

---
 include/linux/msi.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index b54010b..70cc6a5 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -2,6 +2,20 @@
 #ifndef LINUX_MSI_H
 #define LINUX_MSI_H
 
+/*
+ * This header file contains MSI data structures and functions which are
+ * only relevant for:
+ *	- Interrupt core code
+ *	- PCI/MSI core code
+ *	- MSI interrupt domain implementations
+ *	- IOMMU, low level VFIO, NTB and other justified exceptions
+ *	  dealing with low level MSI details.
+ *
+ * Regular device drivers have no business with any of these functions and
+ * especially storing MSI descriptor pointers in random code is considered
+ * abuse. The only function which is relevant for drivers is msi_get_virq().
+ */
+
 #include <linux/cpumask.h>
 #include <linux/mutex.h>
 #include <linux/list.h>