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* BadRAM: Rename pattern -> patterns * BadRAM: Refactor COMBINE_MASK and add clarifying comment * BadRAM: Extract DEFAULT_MASK into variable * BadRAM: Add is_covered() for checking if pattern is already covered by one of the existing patterns * BadRAM: Initialize patterns to 0 * BadRAM: Change how addr/masks are merged to minimize number of addresses covered by badram Prior to this patch, a list of up to MAX_PATTERNS (=10) addr/mask tuples (aka. pattern) were maintained, adding failing addresses one by one to the list until it was full. When full, space was created by forcing a merge of the new address with the existing pattern that would grow the least (with regards to number of addresses covered by the pattern) by merging it with the new address. This can lead to a great imbalance in the number of addresses covered by the patterns. Consider the following: MAX_PATTERNS=4 (for illustrative purposes). The following addresses are faulted and added to patterns: 0x00, 0x10, 0x20, 0x68, 0xa0, 0xb0, 0xc0, 0xd0 This is the end result with the implementation prior to this commit: patterns = [ (0x00, 0xe8), (0x00, 0x18), (0x68, 0xf8), (0x90, 0x98) ] Total addresses covered: 120. This commit changes how the merges are done, not only considering a merge between the new address and existing patterns, but also between existing patterns. It keeps the patterns in ascending order (by .addr) in patterns, and a new address is always inserted into patterns (even if num_patterns == MAX_PATTERNS, patterns is of MAX_PATTERNS+1 size). Then, if num_patterns > MAX_PATTERNS, we find the pair of patterns (only considering neighbours, assuming for any pattern i, i-1 or i+1 will be the best candidate for a merge) that would be the cheapest to merge (using the same metric as prior to this patch), and merge those. With this commit, this is the result of the exact same sequence of addresses as above: [ (0x00, 0xe0), (0x68, 0xf8), (0xa0, 0xe8), (0xc0, 0xe8) ] Total addresses covered: 72. A drawback of the current implementation (as compared to the prior) is that it does not make any attempt at merging patterns until num_patterns == MAX_PATTERNS, which can lead to having several patterns that could've been merged into one at no additional cost. I.e.: patterns = [ (0x00, 0xf8), (0x08, 0xf8) ] can appear, even if patterns = [ (0x00, 0xf0) ] represents the exact same addresses with one pattern instead of two. * fixup! BadRAM: Change how addr/masks are merged to minimize number of addresses covered by badram Co-authored-by: Anders Wenhaug <anders.wenhaug@solutionseeker.no>