| 1 | |
| 2 | |
| 3 | * Common code to handle absent "placeholder" devices
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| 4 | * Copyright 2001 Resilience Corporation <[email protected]>
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| 5 | *
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| 6 | * This map driver is used to allocate "placeholder" MTD
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| 7 | * devices on systems that have socketed/removable media.
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| 8 | * Use of this driver as a fallback preserves the expected
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| 9 | * registration of MTD device nodes regardless of probe outcome.
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| 10 | * A usage example is as follows:
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| 11 | *
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| 12 | * my_dev[i] = do_map_probe("cfi", &my_map[i]);
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| 13 | * if(NULL == my_dev[i]) {
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| 14 | * my_dev[i] = do_map_probe("map_absent", &my_map[i]);
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| 15 | * }
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| 16 | *
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| 17 | * Any device 'probed' with this driver will return -ENODEV
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| 18 | * upon open.
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| 19 |
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| 20 |
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| 21 | #include <linux/module.h>
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| 22 | #include <linux/types.h>
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| 23 | #include <linux/kernel.h>
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| 24 | #include <linux/errno.h>
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| 25 | #include <linux/slab.h>
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| 26 | #include <linux/init.h>
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| 27 | #include <linux/mtd/mtd.h>
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| 28 | #include <linux/mtd/map.h>
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| 29 |
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| 30 | static int map_absent_read (struct mtd_info *, loff_t, size_t, size_t *, u_char *);
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| 31 | static int map_absent_write (struct mtd_info *, loff_t, size_t, size_t *, const u_char *);
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| 32 | static int map_absent_erase (struct mtd_info *, struct erase_info *);
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| 33 | static void map_absent_sync (struct mtd_info *);
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| 34 | static struct mtd_info *map_absent_probe(struct map_info *map);
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| 35 | static void map_absent_destroy (struct mtd_info *);
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| 36 |
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| 37 |
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| 38 | static struct mtd_chip_driver map_absent_chipdrv = {
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| 39 | .probe = map_absent_probe,
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| 40 | .destroy = map_absent_destroy,
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| 41 | .name = "map_absent",
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| 42 | .module = THIS_MODULE
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| 43 | };
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| 44 |
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| 45 | static struct mtd_info *map_absent_probe(struct map_info *map)
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| 46 | {
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| 47 | struct mtd_info *mtd;
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| 48 |
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| 49 | mtd = kzalloc_obj(*mtd);
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| 50 | if (!mtd) {
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| 51 | return NULL;
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| 52 | }
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| 53 |
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| 54 | map->fldrv = &map_absent_chipdrv;
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| 55 | mtd->priv = map;
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| 56 | mtd->name = map->name;
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| 57 | mtd->type = MTD_ABSENT;
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| 58 | mtd->size = map->size;
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| 59 | mtd->_erase = map_absent_erase;
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| 60 | mtd->_read = map_absent_read;
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| 61 | mtd->_write = map_absent_write;
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| 62 | mtd->_sync = map_absent_sync;
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| 63 | mtd->flags = 0;
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| 64 | mtd->erasesize = PAGE_SIZE;
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| 65 | mtd->writesize = 1;
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| 66 |
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| 67 | __module_get(THIS_MODULE);
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| 68 | return mtd;
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| 69 | }
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| 70 |
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| 71 |
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| 72 | static int map_absent_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf)
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| 73 | {
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| 74 | return -ENODEV;
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| 75 | }
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| 76 |
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| 77 | static int map_absent_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen, const u_char *buf)
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| 78 | {
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| 79 | return -ENODEV;
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| 80 | }
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| 81 |
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| 82 | static int map_absent_erase(struct mtd_info *mtd, struct erase_info *instr)
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| 83 | {
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| 84 | return -ENODEV;
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| 85 | }
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| 86 |
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| 87 | static void map_absent_sync(struct mtd_info *mtd)
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| 88 | {
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| 89 |
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| 90 | }
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| 91 |
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| 92 | static void map_absent_destroy(struct mtd_info *mtd)
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| 93 | {
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| 94 |
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| 95 | }
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| 96 |
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| 97 | static int __init map_absent_init(void)
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| 98 | {
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| 99 | register_mtd_chip_driver(&map_absent_chipdrv);
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| 100 | return 0;
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| 101 | }
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| 102 |
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| 103 | static void __exit map_absent_exit(void)
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| 104 | {
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| 105 | unregister_mtd_chip_driver(&map_absent_chipdrv);
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| 106 | }
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| 107 |
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| 108 | module_init(map_absent_init);
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| 109 | module_exit(map_absent_exit);
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| 110 |
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| 111 | MODULE_LICENSE("GPL");
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| 112 | MODULE_AUTHOR("Resilience Corporation - Eric Brower <[email protected]>");
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| 113 | MODULE_DESCRIPTION("Placeholder MTD chip driver for 'absent' chips");
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