[XS] Change in flashrom[main]: Add clarification to struct flash_region on chipoff_t

[Peter Marheine (Code Review)]

Peter Marheine has submitted this change. ( https://review.coreboot.org/c/flashrom/+/82677?usp=email )

(

1 is the latest approved patch-set.
No files were changed between the latest approved patch-set and the submitted one.
 )Change subject: Add clarification to struct flash_region on chipoff_t
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Add clarification to struct flash_region on chipoff_t

Although chipoff_t is fairly clearly documented on its own, it seems
fairly frequent that developers will treat the end address of a flash
region as an exclusive upper bound rather than the inclusive one it
should be; for example CB:82496 fixes an incorrect use that affected
multiple sites, and CB:73571 stemmed from a similar cause. Add a
clarifying comment to call attention to this, to help programmers avoid
making similar mistakes in the future.

Change-Id: I80b61a87ca31bd5a116224aadb4e211ee6841e1f
Signed-off-by: Peter Marheine 
Reviewed-on: https://review.coreboot.org/c/flashrom/+/82677
Reviewed-by: Hsuan-ting Chen 
Reviewed-by: Anastasia Klimchuk 
Tested-by: build bot (Jenkins) 
---
M include/layout.h
1 file changed, 5 insertions(+), 0 deletions(-)

Approvals:
  Anastasia Klimchuk: Looks good to me, approved
  build bot (Jenkins): Verified
  Hsuan-ting Chen: Looks good to me, but someone else must approve

diff --git a/include/layout.h b/include/layout.h
index 5614bea..d03a15b 100644
--- a/include/layout.h
+++ b/include/layout.h
@@ -37,6 +37,11 @@

struct flash_region {
    char *name;
+	/*
+	 * Note that because start and end are chipoff_t, end is an inclusive upper
+	 * bound: the length of a region is (end - start + 1) bytes and it is
+	 * impossible to represent a region with zero length.
+	 */
    chipoff_t start;
    chipoff_t end;
    bool read_prot;