libie: add adminq helper for converting err to str

Add a new module for common handling of Admin Queue related logic.
Start by a helper for error to string conversion. This lives inside
libie/, but is a separate module what follows our logic of splitting
into topical modules, to avoid pulling in not needed stuff, and have
better organization in general.

Olek suggested how to better solve the error to string conversion.

It will be used in follow-up patches in ice, i40e and iavf.

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/libie/Kconfig

@@ -8,3 +8,9 @@ config LIBIE
 	  libie (Intel Ethernet library) is a common library built on top of
 	  libeth and containing vendor-specific routines shared between several
 	  Intel Ethernet drivers.
+
+config LIBIE_ADMINQ
+	tristate
+	help
+	  Helper functions used by Intel Ethernet drivers for administration
+	  queue command interface (aka adminq).

drivers/net/ethernet/intel/libie/Makefile

@@ -4,3 +4,7 @@
 obj-$(CONFIG_LIBIE)	+= libie.o
 
 libie-y			:= rx.o
+
+obj-$(CONFIG_LIBIE_ADMINQ) 	+= libie_adminq.o
+
+libie_adminq-y			:= adminq.o

drivers/net/ethernet/intel/libie/adminq.c

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (C) 2025 Intel Corporation */
+
+#include <linux/module.h>
+#include <linux/net/intel/libie/adminq.h>
+
+static const char * const libie_aq_str_arr[] = {
+#define LIBIE_AQ_STR(x)					\
+	[LIBIE_AQ_RC_##x]	= "LIBIE_AQ_RC" #x
+	LIBIE_AQ_STR(OK),
+	LIBIE_AQ_STR(EPERM),
+	LIBIE_AQ_STR(ENOENT),
+	LIBIE_AQ_STR(ESRCH),
+	LIBIE_AQ_STR(EIO),
+	LIBIE_AQ_STR(EAGAIN),
+	LIBIE_AQ_STR(ENOMEM),
+	LIBIE_AQ_STR(EACCES),
+	LIBIE_AQ_STR(EBUSY),
+	LIBIE_AQ_STR(EEXIST),
+	LIBIE_AQ_STR(EINVAL),
+	LIBIE_AQ_STR(ENOSPC),
+	LIBIE_AQ_STR(ENOSYS),
+	LIBIE_AQ_STR(EMODE),
+	LIBIE_AQ_STR(ENOSEC),
+	LIBIE_AQ_STR(EBADSIG),
+	LIBIE_AQ_STR(ESVN),
+	LIBIE_AQ_STR(EBADMAN),
+	LIBIE_AQ_STR(EBADBUF),
+#undef LIBIE_AQ_STR
+	"LIBIE_AQ_RC_UNKNOWN",
+};
+
+#define __LIBIE_AQ_STR_NUM (ARRAY_SIZE(libie_aq_str_arr) - 1)
+
+/**
+ * libie_aq_str - get error string based on aq error
+ * @err: admin queue error type
+ *
+ * Return: error string for passed error code
+ */
+const char *libie_aq_str(enum libie_aq_err err)
+{
+	if (err >= ARRAY_SIZE(libie_aq_str_arr) ||
+	    !libie_aq_str_arr[err])
+		err = __LIBIE_AQ_STR_NUM;
+
+	return libie_aq_str_arr[err];
+}
+EXPORT_SYMBOL_NS_GPL(libie_aq_str, "LIBIE_ADMINQ");
+
+MODULE_DESCRIPTION("Intel(R) Ethernet common library - adminq helpers");
+MODULE_LICENSE("GPL");

include/linux/net/intel/libie/adminq.h

@@ -303,4 +303,6 @@ static inline void *libie_aq_raw(struct libie_aq_desc *desc)
 	return &desc->params.raw;
 }
 
+const char *libie_aq_str(enum libie_aq_err err);
+
 #endif /* __LIBIE_ADMINQ_H */