flashchips,writeprotect_ranges: add range decoding function

Allow chips to specify functions that map status register bits to
protection ranges. These are used to enumerate available ranges and
determine the protection state of chips. The patch also adds a range
decoding function for the example chips. Many other chips can also be
handled by it, though some will require different functions (e.g.
MX25L6406 and related chips).

Another approach that has been tried in cros flashrom is maintaining
tables of range data, but it quickly becomes error prone and hard to
validate.

Using a function to interpret the ranges allows compact encoding with
most chips and is flexible enough to allow chips with less predictable
ranges to be handled as well.

BUG=b:195381327,b:153800563
BRANCH=none
TEST=dumped range tables, checked against datasheets

Change-Id: Id163ed80938a946a502ed116e48e8236e36eb203
Signed-off-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/58480
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/flash.h b/flash.h
index b935e9bc4..f63aa5d36 100644
--- a/flash.h
+++ b/flash.h
@@ -195,6 +195,8 @@ struct reg_bit_info {
 	} writability;
 };
 
+struct wp_bits;
+
 struct flashchip {
 	const char *vendor;
 	const char *name;
@@ -305,6 +307,10 @@ struct flashchip {
 		/* Complement bit (CMP) */
 		struct reg_bit_info cmp;
 	} reg_bits;
+
+	/* Function that takes a set of WP config bits (e.g. BP, SEC, TB, etc) */
+	/* and determines what protection range they select. */
+	void (*decode_range)(size_t *start, size_t *len, const struct wp_bits *, size_t chip_len);
 };
 
 typedef int (*chip_restore_fn_cb_t)(struct flashctx *flash, uint8_t status);