The pcie_link_speed[] array is indexed by PCIe generation numbers
(1 = 2.5 GT/s, 2 = 5 GT/s, ...).  Several drivers use it directly,
which can lead to out-of-bounds accesses if an invalid generation
number is used.

Introduce a helper function pcie_get_link_speed() that returns the
corresponding enum pci_bus_speed value for a given generation number,
or PCI_SPEED_UNKNOWN if the generation is out of range.  This will
allow us to safely handle invalid values after the range check is
removed from of_pci_get_max_link_speed().

Signed-off-by: Hans Zhang <18255117159@163.com>
---
 drivers/pci/pci.h   |  2 ++
 drivers/pci/probe.c | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 13d998fbacce..6bf3e59f42e5 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -108,6 +108,8 @@ struct pcie_tlp_log;
 				 PCI_EXP_DEVCTL_FERE | PCI_EXP_DEVCTL_URRE)
 
 extern const unsigned char pcie_link_speed[];
+unsigned char pcie_get_link_speed(int speed);
+
 extern bool pci_early_dump;
 
 extern struct mutex pci_rescan_remove_lock;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index bccc7a4bdd79..a95afbcee421 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -783,6 +783,22 @@ const unsigned char pcie_link_speed[] = {
 };
 EXPORT_SYMBOL_GPL(pcie_link_speed);
 
+/**
+ * pcie_link_speed_value - Get speed value from PCIe generation number
+ * @speed: PCIe speed (1-based: 1 = 2.5GT, 2 = 5GT, ...)
+ *
+ * Returns the speed value (e.g., PCIE_SPEED_2_5GT) if @speed is valid,
+ * otherwise returns PCI_SPEED_UNKNOWN.
+ */
+unsigned char pcie_get_link_speed(int speed)
+{
+	if (speed <= 0 || speed >= ARRAY_SIZE(pcie_link_speed))
+		return PCI_SPEED_UNKNOWN;
+
+	return pcie_link_speed[speed];
+}
+EXPORT_SYMBOL_GPL(pcie_get_link_speed);
+
 const char *pci_speed_string(enum pci_bus_speed speed)
 {
 	/* Indexed by the pci_bus_speed enum */
-- 
2.34.1

Hi Hans,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 80234b5ab240f52fa45d201e899e207b9265ef91]

url:    https://github.com/intel-lab-lkp/linux/commits/Hans-Zhang/PCI-Add-pcie_get_link_speed-helper-for-safe-array-access/20260313-220734
base:   80234b5ab240f52fa45d201e899e207b9265ef91
patch link:    https://lore.kernel.org/r/20260312163652.113228-2-18255117159%40163.com
patch subject: [PATCH v8 1/5] PCI: Add pcie_get_link_speed() helper for safe array access
config: alpha-allnoconfig (https://download.01.org/0day-ci/archive/20260314/202603140748.u17h0ZM8-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260314/202603140748.u17h0ZM8-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603140748.u17h0ZM8-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/pci/probe.c:793 expecting prototype for pcie_link_speed_value(). Prototype was for pcie_get_link_speed() instead

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Hi Hans,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 80234b5ab240f52fa45d201e899e207b9265ef91]

url:    https://github.com/intel-lab-lkp/linux/commits/Hans-Zhang/PCI-Add-pcie_get_link_speed-helper-for-safe-array-access/20260313-220734
base:   80234b5ab240f52fa45d201e899e207b9265ef91
patch link:    https://lore.kernel.org/r/20260312163652.113228-2-18255117159%40163.com
patch subject: [PATCH v8 1/5] PCI: Add pcie_get_link_speed() helper for safe array access
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260313/202603131934.SHJnSGL9-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260313/202603131934.SHJnSGL9-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603131934.SHJnSGL9-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/pci/probe.c:793 expecting prototype for pcie_link_speed_value(). Prototype was for pcie_get_link_speed() instead

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki