1 files changed, 113 insertions, 0 deletions
diff --git a/drivers/mtd/chips/map_absent.c b/drivers/mtd/chips/map_absent.c
new file mode 100644
index 000000000..fc68557f4
--- /dev/null
+++ b/drivers/mtd/chips/map_absent.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Common code to handle absent "placeholder" devices
+ * Copyright 2001 Resilience Corporation <ebrower@resilience.com>
+ *
+ * This map driver is used to allocate "placeholder" MTD
+ * devices on systems that have socketed/removable media.
+ * Use of this driver as a fallback preserves the expected
+ * registration of MTD device nodes regardless of probe outcome.
+ * A usage example is as follows:
+ *
+ *		my_dev[i] = do_map_probe("cfi", &my_map[i]);
+ *		if(NULL == my_dev[i]) {
+ *			my_dev[i] = do_map_probe("map_absent", &my_map[i]);
+ *		}
+ *
+ * Any device 'probed' with this driver will return -ENODEV
+ * upon open.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/map.h>
+
+static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
+static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
+static int map_absent_erase (struct mtd_info *, struct erase_info *);
+static void map_absent_sync (struct mtd_info *);
+static struct mtd_info *map_absent_probe(struct map_info *map);
+static void map_absent_destroy (struct mtd_info *);
+
+
+static struct mtd_chip_driver map_absent_chipdrv = {
+	.probe		= map_absent_probe,
+	.destroy	= map_absent_destroy,
+	.name		= "map_absent",
+	.module		= THIS_MODULE
+};
+
+static struct mtd_info *map_absent_probe(struct map_info *map)
+{
+	struct mtd_info *mtd;
+
+	mtd = kzalloc(sizeof(*mtd), GFP_KERNEL);
+	if (!mtd) {
+		return NULL;
+	}
+
+	map->fldrv 	= &map_absent_chipdrv;
+	mtd->priv 	= map;
+	mtd->name 	= map->name;
+	mtd->type 	= MTD_ABSENT;
+	mtd->size 	= map->size;
+	mtd->_erase 	= map_absent_erase;
+	mtd->_read 	= map_absent_read;
+	mtd->_write 	= map_absent_write;
+	mtd->_sync 	= map_absent_sync;
+	mtd->flags 	= 0;
+	mtd->erasesize  = PAGE_SIZE;
+	mtd->writesize  = 1;
+
+	__module_get(THIS_MODULE);
+	return mtd;
+}
+
+
+static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
+{
+	return -ENODEV;
+}
+
+static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
+{
+	return -ENODEV;
+}
+
+static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	return -ENODEV;
+}
+
+static void map_absent_sync(struct mtd_info *mtd)
+{
+	/* nop */
+}
+
+static void map_absent_destroy(struct mtd_info *mtd)
+{
+	/* nop */
+}
+
+static int __init map_absent_init(void)
+{
+	register_mtd_chip_driver(&map_absent_chipdrv);
+	return 0;
+}
+
+static void __exit map_absent_exit(void)
+{
+	unregister_mtd_chip_driver(&map_absent_chipdrv);
+}
+
+module_init(map_absent_init);
+module_exit(map_absent_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Resilience Corporation - Eric Brower <ebrower@resilience.com>");
+MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");