diff --git a/chipdrivers.h b/chipdrivers.h
index 149620a..6b3a334 100644
--- a/chipdrivers.h
+++ b/chipdrivers.h
@@ -209,5 +209,8 @@
 
 /* writeprotect_ranges.c */
 void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_64k_block(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_bit_cmp(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
+void decode_range_spi25_2x_block(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
 
 #endif /* !__CHIPDRIVERS_H__ */
diff --git a/writeprotect_ranges.c b/writeprotect_ranges.c
index 04e3881..d15ba5d 100644
--- a/writeprotect_ranges.c
+++ b/writeprotect_ranges.c
@@ -17,11 +17,11 @@
 #include "writeprotect.h"
 #include "chipdrivers.h"
 
-/*
- * Protection range calculation that works with many common SPI flash chips.
- */
-void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+static void decode_range_generic(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len,
+				 bool fixed_block_len, bool apply_cmp_to_bp, int coeff_offset)
 {
+	const bool cmp = bits->cmp_bit_present && bits->cmp == 1;
+
 	/* Interpret BP bits as an integer */
 	size_t i;
 	size_t bp = 0;
@@ -32,6 +32,15 @@
 		bp_max |= 1 << i;
 	}
 
+	/*
+	 * Most chips: the CMP bit only negates the range.
+	 *
+	 * Some MX chips: the CMP bit negates the BP bits and the range.
+	 * (CMP bit is often the MSB BP bit in such chips.)
+	 */
+	if (cmp && apply_cmp_to_bp)
+		bp ^= bp_max;
+
 	if (bp == 0) {
 		/* Special case: all BP bits are 0 => no write protection */
 		*len = 0;
@@ -41,14 +50,14 @@
 	} else {
 		/*
 		 * Usual case: the BP bits encode a coefficient in the form
-		 * `coeff = 2 ** (bp - 1)`.
+		 * `coeff = 2 ** (bp - offset)` where `offset == 1`.
 		 *
 		 * The range's length is given by multiplying the coefficient
 		 * by a base unit, usually a 4K sector or a 64K block.
 		 */
 
-		size_t coeff     = 1 << (bp - 1);
-		size_t max_coeff = 1 << (bp_max - 2);
+		size_t coeff     = 1 << (bp - coeff_offset);
+		size_t max_coeff = 1 << (bp_max - coeff_offset - 1);
 
 		size_t sector_len        = 4  * KiB;
 		size_t default_block_len = 64 * KiB;
@@ -63,14 +72,19 @@
 		} else {
 			/*
 			 * SEC=0 or is not present, protect blocks.
-			 *
+			 */
+			size_t block_len = default_block_len;
+
+			/*
 			 * With very large chips, the 'block' size can be
 			 * larger than 64K. This occurs when a larger block
 			 * size is needed so that half the chip can be
 			 * protected by the maximum possible coefficient.
 			 */
-			size_t min_block_len = chip_len / 2 / max_coeff;
-			size_t block_len = max(min_block_len, default_block_len);
+			if (!fixed_block_len) {
+				size_t min_block_len = chip_len / 2 / max_coeff;
+				block_len = max(min_block_len, default_block_len);
+			}
 
 			*len = min(block_len * coeff, chip_len);
 		}
@@ -80,7 +94,7 @@
 	bool protect_top = bits->tb_bit_present ? (bits->tb == 0) : 1;
 
 	/* Apply CMP bit */
-	if (bits->cmp_bit_present && bits->cmp == 1) {
+	if (cmp) {
 		*len = chip_len - *len;
 		protect_top = !protect_top;
 	}
@@ -91,3 +105,41 @@
 	else
 		*start = 0;
 }
+
+/*
+ * Protection range calculation that works with many common SPI flash chips.
+ */
+void decode_range_spi25(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/1);
+}
+
+/*
+ * Do not adjust block size to be able to fill half of the chip.
+ */
+void decode_range_spi25_64k_block(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/true, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/1);
+}
+
+/*
+ * Inverts BP bits when CMP is set and treats all ones in BP bits as a request to protect whole chip regardless
+ * of the CMP bit.
+ */
+void decode_range_spi25_bit_cmp(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/true, /*coeff_offset=*/1);
+}
+
+/*
+ * This multiplies coefficient by 2.  To be used with chips which have more BP bits than needed, such that the
+ * most significant BP bit effectively acts as "protect whole chip" flag.
+ */
+void decode_range_spi25_2x_block(size_t *start, size_t *len, const struct wp_bits *bits, size_t chip_len)
+{
+	decode_range_generic(start, len, bits, chip_len,
+			     /*fixed_block_len=*/false, /*apply_cmp_to_bp=*/false, /*coeff_offset=*/0);
+}