[PATCH v3 i-g-t 05/10] lib/igt_sriov_device: Add helper for PF/VF sysfs path formatting

[Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>]

Add igt_sriov_func_str() — a small utility that returns "pf" for
function 0 and "vf%u" for any VF index. This helper allows callers
to build SR-IOV sysfs paths without duplicating PF/VF conditional
logic.

Signed-off-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Reviewed-by: Lukasz Laguna <lukasz.laguna@intel.com>
Cc: Adam Miszczak <adam.miszczak@linux.intel.com>
Cc: Jakub Kolakowski <jakub1.kolakowski@intel.com>
Cc: Lukasz Laguna <lukasz.laguna@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
---
 lib/igt_sriov_device.c | 19 +++++++++++++++++++
 lib/igt_sriov_device.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/lib/igt_sriov_device.c b/lib/igt_sriov_device.c
index ffa996d6b..788ffbfa1 100644
--- a/lib/igt_sriov_device.c
+++ b/lib/igt_sriov_device.c
@@ -42,6 +42,25 @@ bool igt_sriov_is_pf(int device)
 	return value > 0;
 }
 
+/**
+ * igt_sriov_func_str - Return "pf" or "vf%u" label for a function number
+ * @vf_num: 0 for PF, >0 for VF index
+ *
+ * Helper for constructing SR-IOV sysfs paths.
+ *
+ * Returns: "pf" for @vf_num == 0, otherwise "vf%u".
+ */
+const char *igt_sriov_func_str(unsigned int vf_num)
+{
+	static __thread char buf[16];
+
+	if (vf_num == 0)
+		return "pf";
+
+	snprintf(buf, sizeof(buf), "vf%u", vf_num);
+	return buf;
+}
+
 static bool __pf_attr_get_u32(int pf, const char *attr, uint32_t *value)
 {
 	int sysfs;
diff --git a/lib/igt_sriov_device.h b/lib/igt_sriov_device.h
index 930e97982..84d29b1bb 100644
--- a/lib/igt_sriov_device.h
+++ b/lib/igt_sriov_device.h
@@ -34,6 +34,7 @@ int igt_sriov_device_sysfs_open(int pf, unsigned int vf_num);
 bool igt_sriov_device_reset_exists(int pf, unsigned int vf_num);
 bool igt_sriov_device_reset(int pf, unsigned int vf_num);
 bool intel_is_vf_device(int device);
+const char *igt_sriov_func_str(unsigned int vf_num);
 
 /**
  * __is_valid_range - Helper to check VF range is valid
-- 
2.43.0