From 2371f60ad9a1c171c56036e9bcf6fc25391b47ae Mon Sep 17 00:00:00 2001
From: DAEYEONG LEE <daeyeong.lee@metisx.com>
Date: Thu, 23 Jul 2026 15:23:51 +0900
Subject: [PATCH] fix(driver): guard el9 (RHEL 9) backported kernel APIs with
 RHEL_RELEASE_CODE

RHEL 9 ships a 5.14 kernel but backports class_create(), vm_flags,
device_find_child match, and devnode signatures, so LINUX_VERSION_CODE alone
selected the wrong branch and mx_dma failed to build. Gate the four sites on
RHEL_RELEASE_CODE >= 9.6 as well.
---
 core_v1.c | 2 +-
 init.c    | 6 +++---
 mx_dma.h  | 8 ++++++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/core_v1.c b/core_v1.c
index 9d6fa97..62e2d23 100644
--- a/core_v1.c
+++ b/core_v1.c
@@ -429,7 +429,7 @@ static int mxdma_bar_mmap_v1(struct mx_pci_dev *mx_pdev,
 	}
 
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0)
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 3, 0) || RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(9, 6)
 	vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
 #else
 	vma->vm_flags |= (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
diff --git a/init.c b/init.c
index 60ed271..c7dab2d 100644
--- a/init.c
+++ b/init.c
@@ -551,7 +551,7 @@ static const struct pci_device_id pci_ids[] = {
 MODULE_DEVICE_TABLE(pci, pci_ids);
 
 #ifndef CONFIG_WO_CXL
-#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 12, 0)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 12, 0) && RHEL_RELEASE_CODE < RHEL_RELEASE_VERSION(9, 6)
 static int match_mem_prefix(struct device *dev, void *data)
 #else
 static int match_mem_prefix(struct device *dev, const void *data)
@@ -659,7 +659,7 @@ static struct pci_driver pci_driver = {
 };
 #endif
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 1, 6)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 1, 6) && RHEL_RELEASE_CODE < RHEL_RELEASE_VERSION(9, 6)
 static char *mxdma_devnode(struct device *dev, umode_t *mode)
 #else
 static char *mxdma_devnode(const struct device *dev, umode_t *mode)
@@ -715,7 +715,7 @@ static struct notifier_block mxdma_pci_notifier = {
 
 static int mxdma_init(void)
 {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 3, 3)
+#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 3, 3) && RHEL_RELEASE_CODE < RHEL_RELEASE_VERSION(9, 6)
 	mxdma_class = class_create(THIS_MODULE, MXDMA_NODE_NAME);
 #else
 	mxdma_class = class_create(MXDMA_NODE_NAME);
diff --git a/mx_dma.h b/mx_dma.h
index 9a30c02..cd9c2dc 100644
--- a/mx_dma.h
+++ b/mx_dma.h
@@ -8,6 +8,14 @@
 #include <linux/cdev.h>
 #include <linux/delay.h>
 #include <linux/version.h>
+
+/* RHEL ships a 5.14 kernel but backports later mainline APIs, so a bare
+ * LINUX_VERSION_CODE test picks the wrong branch; guards below also gate on
+ * RHEL_RELEASE_CODE, stubbed here to lose every comparison off RHEL. */
+#ifndef RHEL_RELEASE_CODE
+#define RHEL_RELEASE_CODE 0
+#define RHEL_RELEASE_VERSION(a, b) 1
+#endif
 #include <linux/errno.h>
 #include <linux/pci.h>
 #include <linux/aer.h>