xref: /btstack/platform/embedded/btstack_tlv_flash_bank.c (revision 57f681c0f6daf7a74c0508286bfbd7ba6590c7c9)
1 /*
2  * Copyright (C) 2017 BlueKitchen GmbH
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holders nor the names of
14  *    contributors may be used to endorse or promote products derived
15  *    from this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BLUEKITCHEN
21  * GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
23  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
24  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
25  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
27  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28  * SUCH DAMAGE.
29  *
30  */
31 
32 #define BTSTACK_FILE__ "btstack_tlv_flash_bank.c"
33 
34 #include "btstack_tlv.h"
35 #include "btstack_tlv_flash_bank.h"
36 #include "btstack_debug.h"
37 #include "btstack_util.h"
38 #include "btstack_debug.h"
39 
40 #include <string.h>
41 #include <inttypes.h>
42 
43 // Header:
44 // - Magic: 'BTstack'
45 // - Status:
46 //   - bits 765432: reserved
47 //	 - bits 10:     epoch
48 
49 // Entries
50 // - Tag: 32 bit
51 // - Len: 32 bit
52 // - if ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD is used
53 //    - padding to align delete field
54 //    - Delete: 32 bit
55 //    - padding to align value field
56 // - Value: Len in bytes
57 
58 // Alignment
59 // Tag is aligned to the alignment from hal_flash_bank_t
60 // If ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD is used, both Delete and Value are aligned, too
61 
62 // ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
63 //
64 // Most Flash implementations allow to:
65 // - erase sector -> all values are 0xff
66 // - write value (1s -> 0s)
67 // - overwrite value with zero (remaining 1s -> 0s)
68 //
69 // We use the ability to overwrite a value with zeros to mark deleted entries (by writing zero into the tag field).
70 // Some targets, E.g. Kinetix K64F, do not allow for that.
71 //
72 // With ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD an extra field is reserved to indicate a deleted tag, while keeping main logic
73 //
74 // With ENABLE_TLV_FLASH_WRITE_ONCE, tags are never marked as deleted. Instead, an emtpy tag will be written instead.
75 //     Also, lookup and migrate requires to always search until the end of the valid bank
76 
77 #if defined (ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD) && defined (ENABLE_TLV_FLASH_WRITE_ONCE)
78 #error "Please define either ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD or ENABLE_TLV_FLASH_WRITE_ONCE"
79 #endif
80 
81 #define BTSTACK_TLV_BANK_HEADER_LEN  8
82 #define BTSTACK_TLV_ENTRY_HEADER_LEN 8
83 
84 #ifndef BTSTACK_FLASH_ALIGNMENT_MAX
85 #define BTSTACK_FLASH_ALIGNMENT_MAX 16
86 #endif
87 
88 static const char * btstack_tlv_header_magic = "BTstack";
89 
90 // TLV Iterator
91 typedef struct {
92 	int 	 bank;
93 	uint32_t offset;
94     uint32_t size;
95 	uint32_t tag;
96 	uint32_t len;
97 } tlv_iterator_t;
98 
99 static uint32_t btstack_tlv_flash_bank_align_size(btstack_tlv_flash_bank_t * self, uint32_t size){
100 	uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
101 	return (size + alignment - 1) & ~(alignment - 1);
102 }
103 
104 static uint32_t btstack_tlv_flash_bank_aligned_entry_size(btstack_tlv_flash_bank_t * self, uint32_t size) {
105 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
106     // entry header and delete fields are already padded
107     return self->entry_header_len + self->delete_tag_len + btstack_tlv_flash_bank_align_size(self, size);
108 #else
109     // otherwise, data starts right after entry header
110     return btstack_tlv_flash_bank_align_size(self, self->entry_header_len + size);
111 #endif
112 }
113 
114 // support unaligned flash read/writes
115 // strategy: increase size to meet alignment, perform unaligned read/write of last chunk with helper buffer
116 
117 static void btstack_tlv_flash_bank_read(btstack_tlv_flash_bank_t * self, int bank, uint32_t offset, uint8_t * buffer, uint32_t size){
118 
119 	// read main data
120 	uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
121 	uint32_t lower_bits = size & (alignment - 1);
122 	uint32_t size_aligned = size - lower_bits;
123 	if (size_aligned){
124 		self->hal_flash_bank_impl->read(self->hal_flash_bank_context, bank, offset, buffer, size_aligned);
125 		buffer += size_aligned;
126 		offset += size_aligned;
127 		size   -= size_aligned;
128 	}
129 
130 	// read last part
131 	if (size == 0) return;
132 	uint8_t alignment_block[BTSTACK_FLASH_ALIGNMENT_MAX];
133 	self->hal_flash_bank_impl->read(self->hal_flash_bank_context, bank, offset, alignment_block, alignment);
134 	memcpy(buffer, alignment_block, size);
135 }
136 
137 static void btstack_tlv_flash_bank_write(btstack_tlv_flash_bank_t * self, int bank, uint32_t offset, const uint8_t * buffer, uint32_t size){
138 
139 	// write main data
140 	uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
141 	uint32_t lower_bits = size & (alignment - 1);
142 	uint32_t size_aligned = size - lower_bits;
143 	if (size_aligned){
144 		self->hal_flash_bank_impl->write(self->hal_flash_bank_context, bank, offset, buffer, size_aligned);
145 		buffer += size_aligned;
146 		offset += size_aligned;
147 		size   -= size_aligned;
148 	}
149 
150 	// write last part
151 	if (size == 0) return;
152 	uint8_t alignment_block[BTSTACK_FLASH_ALIGNMENT_MAX];
153 	memset(alignment_block, 0xff, alignment);
154 	memcpy(alignment_block, buffer, lower_bits);
155 	self->hal_flash_bank_impl->write(self->hal_flash_bank_context, bank, offset, alignment_block, alignment);
156 }
157 
158 
159 // iterator
160 
161 static void btstack_tlv_flash_bank_iterator_fetch_tag_len(btstack_tlv_flash_bank_t * self, tlv_iterator_t * it){
162     // abort if header doesn't fit into remaining space
163     if (it->offset + self->entry_header_len + self->delete_tag_len >= self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context)){
164         it->tag = 0xffffffff;
165         return;
166     }
167 
168 	uint8_t entry[BTSTACK_TLV_ENTRY_HEADER_LEN];
169 	btstack_tlv_flash_bank_read(self, it->bank, it->offset, entry, BTSTACK_TLV_ENTRY_HEADER_LEN);
170 	it->tag = big_endian_read_32(entry, 0);
171 	it->len = big_endian_read_32(entry, 4);
172 
173 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
174 	// clear tag, if delete field is set
175 	uint32_t delete_tag;
176 	btstack_tlv_flash_bank_read(self, it->bank, it->offset + self->entry_header_len, (uint8_t *) &delete_tag, 4);
177 	if (delete_tag == 0){
178 		it->tag = 0;
179 	}
180 #endif
181 }
182 
183 static void btstack_tlv_flash_bank_iterator_init(btstack_tlv_flash_bank_t * self, tlv_iterator_t * it, int bank){
184 	memset(it, 0, sizeof(tlv_iterator_t));
185 	it->bank = bank;
186 	it->offset = btstack_tlv_flash_bank_align_size(self, BTSTACK_TLV_BANK_HEADER_LEN);
187     it->size = self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context);
188 	btstack_tlv_flash_bank_iterator_fetch_tag_len(self, it);
189 }
190 
191 static bool btstack_tlv_flash_bank_iterator_has_next(btstack_tlv_flash_bank_t * self, tlv_iterator_t * it){
192 	UNUSED(self);
193 	return it->tag != 0xffffffff;
194 }
195 
196 static void tlv_iterator_fetch_next(btstack_tlv_flash_bank_t * self, tlv_iterator_t * it){
197     it->offset += btstack_tlv_flash_bank_aligned_entry_size(self, it->len);
198 
199 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
200 	// skip delete field
201 	it->offset += self->delete_tag_len;
202 #endif
203 
204 	if (it->offset >= it->size) {
205 		it->tag = 0xffffffff;
206 		it->len = 0;
207 		return;
208 	}
209 	btstack_tlv_flash_bank_iterator_fetch_tag_len(self, it);
210 }
211 
212 //
213 
214 // check both banks for headers and pick the one with the higher epoch % 4
215 // @returns bank or -1 if something is invalid
216 static int btstack_tlv_flash_bank_get_latest_bank(btstack_tlv_flash_bank_t * self){
217  	uint8_t header0[BTSTACK_TLV_BANK_HEADER_LEN];
218  	uint8_t header1[BTSTACK_TLV_BANK_HEADER_LEN];
219  	btstack_tlv_flash_bank_read(self, 0, 0, &header0[0], BTSTACK_TLV_BANK_HEADER_LEN);
220  	btstack_tlv_flash_bank_read(self, 1, 0, &header1[0], BTSTACK_TLV_BANK_HEADER_LEN);
221  	int valid0 = memcmp(header0, btstack_tlv_header_magic, BTSTACK_TLV_BANK_HEADER_LEN-1) == 0;
222  	int valid1 = memcmp(header1, btstack_tlv_header_magic, BTSTACK_TLV_BANK_HEADER_LEN-1) == 0;
223 	if (!valid0 && !valid1) return -1;
224 	if ( valid0 && !valid1) return 0;
225 	if (!valid0 &&  valid1) return 1;
226 	int epoch0 = header0[BTSTACK_TLV_BANK_HEADER_LEN-1] & 0x03;
227 	int epoch1 = header1[BTSTACK_TLV_BANK_HEADER_LEN-1] & 0x03;
228 	if (epoch0 == ((epoch1 + 1) & 0x03)) return 0;
229 	if (epoch1 == ((epoch0 + 1) & 0x03)) return 1;
230 	return -1;	// invalid, must not happen
231 }
232 
233 static void btstack_tlv_flash_bank_write_header(btstack_tlv_flash_bank_t * self, int bank, int epoch){
234 	uint8_t header[BTSTACK_TLV_BANK_HEADER_LEN];
235 	memcpy(&header[0], btstack_tlv_header_magic, BTSTACK_TLV_BANK_HEADER_LEN-1);
236 	header[BTSTACK_TLV_BANK_HEADER_LEN-1] = epoch;
237 	btstack_tlv_flash_bank_write(self, bank, 0, header, BTSTACK_TLV_BANK_HEADER_LEN);
238 }
239 
240 /**
241  * @brief Check if erased from offset
242  */
243 static int btstack_tlv_flash_bank_test_erased(btstack_tlv_flash_bank_t * self, int bank, uint32_t offset){
244 	log_info("test erased: bank %u, offset %u", bank, (unsigned int) offset);
245 	uint32_t size = self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context);
246 	uint8_t buffer[16];
247 	uint8_t empty16[16];
248 	memset(empty16, 0xff, sizeof(empty16));
249 	while (offset < size){
250 		uint32_t copy_size = (offset + sizeof(empty16) < size) ? sizeof(empty16) : (size - offset);
251 		btstack_tlv_flash_bank_read(self, bank, offset, buffer, copy_size);
252 		if (memcmp(buffer, empty16, copy_size) != 0) {
253 			log_info("not erased %x - %x", (unsigned int) offset, (unsigned int) (offset + copy_size));
254 			return 0;
255 		}
256 		offset += copy_size;
257 	}
258 	return 1;
259 }
260 
261 /**
262  * @brief erase bank (only if not already erased)
263  */
264 static void btstack_tlv_flash_bank_erase_bank(btstack_tlv_flash_bank_t * self, int bank){
265 	if (btstack_tlv_flash_bank_test_erased(self, bank, 0)){
266 		log_info("bank %u already erased", bank);
267 	} else {
268 		log_info("bank %u not empty, erase bank", bank);
269 		self->hal_flash_bank_impl->erase(self->hal_flash_bank_context, bank);
270 	}
271 }
272 
273 static void btstack_tlv_flash_bank_migrate(btstack_tlv_flash_bank_t * self){
274 
275 	int next_bank = 1 - self->current_bank;
276 	log_info("migrate bank %u -> bank %u", self->current_bank, next_bank);
277 	// erase bank (if needed)
278 	btstack_tlv_flash_bank_erase_bank(self, next_bank);
279 	uint32_t next_write_pos = btstack_tlv_flash_bank_align_size (self, BTSTACK_TLV_BANK_HEADER_LEN);;
280 
281 	tlv_iterator_t it;
282 	btstack_tlv_flash_bank_iterator_init(self, &it, self->current_bank);
283 	while (btstack_tlv_flash_bank_iterator_has_next(self, &it)){
284 		// skip deleted entries
285 		if (it.tag) {
286 			uint32_t tag_len = it.len;
287 			uint32_t tag_index = it.offset;
288 
289             bool tag_valid = true;
290 
291 #ifdef ENABLE_TLV_FLASH_WRITE_ONCE
292             // search until end for newer entry of same tag
293             tlv_iterator_t it2;
294             memcpy(&it2, &it, sizeof(tlv_iterator_t));
295             while (btstack_tlv_flash_bank_iterator_has_next(self, &it2)){
296                 if ((it2.offset != it.offset) && (it2.tag == it.tag)){
297                     tag_valid = false;
298                     break;
299                 }
300                 tlv_iterator_fetch_next(self, &it2);
301             }
302             if (tag_valid == false){
303 			    log_info("skip pos %u, tag '%x' as newer entry found at %u", (unsigned int) tag_index, (unsigned int) it.tag,
304                     (unsigned int) it2.offset);
305             }
306 #endif
307 
308             if (tag_valid) {
309 
310                 log_info("migrate pos %u, tag '%x' len %u -> new pos %u",
311                          (unsigned int) tag_index, (unsigned int) it.tag, (unsigned int) tag_len, next_write_pos);
312 
313                 uint32_t write_offset = next_write_pos;
314                 uint32_t bytes_to_copy;
315                 uint32_t entry_size = btstack_tlv_flash_bank_aligned_entry_size(self, tag_len);
316 
317 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
318                 // copy in two steps to skip delete field
319 
320                 // copy header
321                 uint8_t header_buffer[BTSTACK_TLV_ENTRY_HEADER_LEN];
322                 btstack_tlv_flash_bank_read(self, self->current_bank, tag_index, header_buffer, BTSTACK_TLV_ENTRY_HEADER_LEN);
323                 btstack_tlv_flash_bank_write(self, next_bank, next_write_pos,    header_buffer, BTSTACK_TLV_ENTRY_HEADER_LEN);
324                 tag_index    += self->entry_header_len + self->delete_tag_len;
325                 write_offset += self->entry_header_len + self->delete_tag_len;
326 
327                 // preparee copy value
328                 bytes_to_copy = tag_len;
329 #else
330                 // copy everything as one block
331                 bytes_to_copy = entry_size;
332 #endif
333 
334                 // copy value
335                 uint8_t copy_buffer[32];
336                 while (bytes_to_copy > 0) {
337                     uint32_t bytes_this_iteration = btstack_min(bytes_to_copy, sizeof(copy_buffer));
338                     btstack_tlv_flash_bank_read(self, self->current_bank, tag_index, copy_buffer, bytes_this_iteration);
339                     btstack_tlv_flash_bank_write(self, next_bank, write_offset, copy_buffer, bytes_this_iteration);
340                     tag_index     += bytes_this_iteration;
341                     write_offset  += bytes_this_iteration;
342                     bytes_to_copy -= bytes_this_iteration;
343                 }
344                 next_write_pos += entry_size;
345             }
346 		}
347 		tlv_iterator_fetch_next(self, &it);
348 	}
349 
350 	// prepare new one
351 	uint8_t epoch_buffer;
352 	btstack_tlv_flash_bank_read(self, self->current_bank, BTSTACK_TLV_BANK_HEADER_LEN-1, &epoch_buffer, 1);
353 	btstack_tlv_flash_bank_write_header(self, next_bank, (epoch_buffer + 1) & 3);
354 	self->current_bank = next_bank;
355 	self->write_offset = next_write_pos;
356 }
357 
358 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
359 static void btstack_tlv_flash_bank_delete_tag_until_offset(btstack_tlv_flash_bank_t * self, uint32_t tag, uint32_t offset){
360 	tlv_iterator_t it;
361 	btstack_tlv_flash_bank_iterator_init(self, &it, self->current_bank);
362 	while (btstack_tlv_flash_bank_iterator_has_next(self, &it) && it.offset < offset){
363 		if (it.tag == tag){
364 			log_info("Erase tag '%x' at position %u", (unsigned int) tag, (unsigned int) it.offset);
365 
366 			// mark entry as invalid
367 			uint32_t zero_value = 0;
368 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
369 			// write delete field after entry header
370 			btstack_tlv_flash_bank_write(self, self->current_bank, it.offset+self->entry_header_len, (uint8_t*) &zero_value, sizeof(zero_value));
371 #else
372             uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
373             if (alignment <= 4){
374                 // if alignment < 4, overwrite only tag with zero value
375                 btstack_tlv_flash_bank_write(self, self->current_bank, it.offset, (uint8_t*) &zero_value, sizeof(zero_value));
376             } else {
377                 // otherwise, overwrite complete entry. This results in a sequence of { tag: 0, len: 0 } entries
378                 uint8_t zero_buffer[32];
379                 memset(zero_buffer, 0, sizeof(zero_buffer));
380                 uint32_t entry_offset = 0;
381                 uint32_t entry_size = btstack_tlv_flash_bank_aligned_entry_size(self, it.len);
382                 while (entry_offset < entry_size) {
383                     uint32_t bytes_to_write = btstack_min(entry_size - entry_offset, sizeof(zero_buffer));
384                     btstack_tlv_flash_bank_write(self, self->current_bank, it.offset + entry_offset, zero_buffer, bytes_to_write);
385                     entry_offset += bytes_to_write;
386                 }
387             }
388 #endif
389 		}
390 		tlv_iterator_fetch_next(self, &it);
391 	}
392 }
393 #endif
394 
395 /**
396  * Get Value for Tag
397  * @param tag
398  * @param buffer
399  * @param buffer_size
400  * @returns size of value
401  */
402 static int btstack_tlv_flash_bank_get_tag(void * context, uint32_t tag, uint8_t * buffer, uint32_t buffer_size){
403 
404 	btstack_tlv_flash_bank_t * self = (btstack_tlv_flash_bank_t *) context;
405 
406 	uint32_t tag_index = 0;
407 	uint32_t tag_len   = 0;
408 	tlv_iterator_t it;
409 	btstack_tlv_flash_bank_iterator_init(self, &it, self->current_bank);
410 	while (btstack_tlv_flash_bank_iterator_has_next(self, &it)){
411 		if (it.tag == tag){
412 			log_info("Found tag '%x' at position %u", (unsigned int) tag, (unsigned int) it.offset);
413 			tag_index = it.offset;
414 			tag_len   = it.len;
415 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
416 			break;
417 #endif
418 		}
419 		tlv_iterator_fetch_next(self, &it);
420 	}
421 	if (tag_index == 0) return 0;
422 	if (!buffer) return tag_len;
423 	int copy_size = btstack_min(buffer_size, tag_len);
424 	uint32_t value_offset = tag_index + self->entry_header_len;
425 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
426 	// skip delete field
427 	value_offset += self->delete_tag_len;
428 #endif
429 	btstack_tlv_flash_bank_read(self, self->current_bank, value_offset, buffer, copy_size);
430 	return copy_size;
431 }
432 
433 /**
434  * Store Tag
435  * @param tag
436  * @param data
437  * @param data_size
438  */
439 static int btstack_tlv_flash_bank_store_tag(void * context, uint32_t tag, const uint8_t * data, uint32_t data_size){
440 
441 	btstack_tlv_flash_bank_t * self = (btstack_tlv_flash_bank_t *) context;
442 
443 	// trigger migration if not enough space
444 	uint32_t required_space = self->entry_header_len + self->delete_tag_len + data_size;
445 	if (self->write_offset + required_space > self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context)){
446 		btstack_tlv_flash_bank_migrate(self);
447 	}
448 
449 	if (self->write_offset + required_space > self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context)){
450 		log_error("couldn't write entry, not enough space left");
451 		return 2;
452 	}
453 
454     // prepare entry
455     log_info("write '%" PRIx32 "', len %" PRIu32 " at %" PRIx32, tag, data_size, self->write_offset);
456 
457     uint8_t alignment_buffer[BTSTACK_FLASH_ALIGNMENT_MAX];
458     memset(alignment_buffer, 0, sizeof(alignment_buffer));
459     big_endian_store_32(alignment_buffer, 0, tag);
460     big_endian_store_32(alignment_buffer, 4, data_size);
461 
462     uint32_t header_len = BTSTACK_TLV_ENTRY_HEADER_LEN;
463     uint32_t value_size = data_size;
464     uint32_t value_offset = self->write_offset + self->entry_header_len;
465 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
466     // skip delete field
467     value_offset += self->delete_tag_len;
468 #else
469     uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
470 
471     // if alignment is larger than the entry header, store parts from value in alignment buffer
472     if (alignment > BTSTACK_TLV_ENTRY_HEADER_LEN){
473         // calculated number of value bytes to store in alignment buffer
474         uint32_t bytes_from_value = btstack_min(alignment - BTSTACK_TLV_ENTRY_HEADER_LEN, value_size);
475 
476         // store parts from value in alignment buffer and update remaining value
477         memcpy(&alignment_buffer[header_len], data, bytes_from_value);
478         header_len += bytes_from_value;
479         data       += bytes_from_value;
480         value_size -= bytes_from_value;
481         value_offset = self->write_offset + alignment;
482     }
483 #endif
484 
485     // write value first
486     if (value_size > 0){
487         btstack_tlv_flash_bank_write(self, self->current_bank, value_offset, data, value_size);
488     }
489 
490     // then entry
491     btstack_tlv_flash_bank_write(self, self->current_bank, self->write_offset, alignment_buffer, header_len);
492 
493 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
494 	// overwrite old entries (if exists)
495 	btstack_tlv_flash_bank_delete_tag_until_offset(self, tag, self->write_offset);
496 #endif
497 
498 	// done
499 	self->write_offset += btstack_tlv_flash_bank_aligned_entry_size(self, data_size);
500 
501 	return 0;
502 }
503 
504 /**
505  * Delete Tag
506  * @param tag
507  */
508 static void btstack_tlv_flash_bank_delete_tag(void * context, uint32_t tag){
509 #ifdef ENABLE_TLV_FLASH_WRITE_ONCE
510     btstack_tlv_flash_bank_store_tag(context, tag, NULL, 0);
511 #else
512     btstack_tlv_flash_bank_t * self = (btstack_tlv_flash_bank_t *) context;
513 	btstack_tlv_flash_bank_delete_tag_until_offset(self, tag, self->write_offset);
514 #endif
515 }
516 
517 static const btstack_tlv_t btstack_tlv_flash_bank = {
518 	/* int  (*get_tag)(..);     */ &btstack_tlv_flash_bank_get_tag,
519 	/* int (*store_tag)(..);    */ &btstack_tlv_flash_bank_store_tag,
520 	/* void (*delete_tag)(v..); */ &btstack_tlv_flash_bank_delete_tag,
521 };
522 
523 /**
524  * Init Tag Length Value Store
525  */
526 const btstack_tlv_t * btstack_tlv_flash_bank_init_instance(btstack_tlv_flash_bank_t * self, const hal_flash_bank_t * hal_flash_bank_impl, void * hal_flash_bank_context){
527 
528     self->hal_flash_bank_impl    = hal_flash_bank_impl;
529     self->hal_flash_bank_context = hal_flash_bank_context;
530     self->delete_tag_len = 0;
531 
532     // BTSTACK_FLASH_ALIGNMENT_MAX must be larger than alignment
533     uint32_t alignment = self->hal_flash_bank_impl->get_alignment(self->hal_flash_bank_context);
534     btstack_assert(BTSTACK_FLASH_ALIGNMENT_MAX >= alignment);
535 
536 #ifdef ENABLE_TLV_FLASH_EXPLICIT_DELETE_FIELD
537 	// set delete tag len
538 	self->delete_tag_len = (uint8_t) btstack_max(4, alignment);
539 	log_info("delete tag len %u", self->delete_tag_len);
540 
541     // set aligned entry header len
542     self->entry_header_len = btstack_tlv_flash_bank_align_size(self, BTSTACK_TLV_ENTRY_HEADER_LEN);
543 	log_info("entry header len %u", self->entry_header_len);
544 #else
545     UNUSED(alignment);
546     // data starts right after entry header
547     self->entry_header_len = BTSTACK_TLV_ENTRY_HEADER_LEN;
548 #endif
549 
550 	// try to find current bank
551 	self->current_bank = btstack_tlv_flash_bank_get_latest_bank(self);
552 	log_info("found bank %d", self->current_bank);
553 	if (self->current_bank >= 0){
554 
555 		// find last entry and write offset
556 		tlv_iterator_t it;
557 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
558 		uint32_t last_tag = 0;
559 		uint32_t last_offset = 0;
560 #endif
561         btstack_tlv_flash_bank_iterator_init(self, &it, self->current_bank);
562 		while (btstack_tlv_flash_bank_iterator_has_next(self, &it)){
563 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
564 			last_tag = it.tag;
565 			last_offset = it.offset;
566 #endif
567 			tlv_iterator_fetch_next(self, &it);
568 		}
569 		self->write_offset = it.offset;
570 
571 		if (self->write_offset <= self->hal_flash_bank_impl->get_size(self->hal_flash_bank_context)){
572 
573 #ifndef ENABLE_TLV_FLASH_WRITE_ONCE
574 			// delete older instances of last_tag
575 			// this handles the unlikely case where MCU did reset after new value + header was written but before delete did complete
576 			if (last_tag){
577 				btstack_tlv_flash_bank_delete_tag_until_offset(self, last_tag, last_offset);
578 			}
579 #endif
580 
581 			// verify that rest of bank is empty
582 			// this handles the unlikely case where MCU did reset after new value was written, but not the tag
583 			if (!btstack_tlv_flash_bank_test_erased(self, self->current_bank, self->write_offset)){
584 				log_info("Flash not empty after last found tag -> migrate");
585 				btstack_tlv_flash_bank_migrate(self);
586 			} else {
587 				log_info("Flash clean after last found tag");
588 			}
589 		} else {
590 			// failure!
591 			self->current_bank = -1;
592 		}
593 	}
594 
595 	if (self->current_bank < 0) {
596 		btstack_tlv_flash_bank_erase_bank(self, 0);
597 		self->current_bank = 0;
598 		btstack_tlv_flash_bank_write_header(self, self->current_bank, 0);	// epoch = 0;
599         self->write_offset = btstack_tlv_flash_bank_align_size (self, BTSTACK_TLV_BANK_HEADER_LEN);
600 	}
601 
602 	log_info("write offset %" PRIx32, self->write_offset);
603 	return &btstack_tlv_flash_bank;
604 }
605 
606