GitLab

I decided to fill in the info for a
few chips to illustrate how this works both for uniform and non-uniform
sector sizes.

struct eraseblock{
int size; /* Eraseblock size */
int count; /* Number of contiguous blocks with that size */
};

struct eraseblock doesn't correspond with a single erase block, but with
a group of contiguous erase blocks having the same size.
Given a (top boot block) flash chip with the following weird, but
real-life structure:

top
16384
8192
8192
32768
65536
65536
65536
65536
65536
65536
65536
bottom

we get the following encoding:
{65536,7},{32768,1},{8192,2},{16384,1}

Although the number of blocks is bigger than 4, the number of block
groups is only 4. If you ever add some flash chips with more than 4
contiguous block groups, the definition will not fit into the 4-member
array anymore and gcc will recognize that and error out. No undetected
overflow possible. In that case, you simply increase array size a bit.
For modern flash chips with uniform erase block size, you only need one
array member anyway.

Of course data types will need to be changed if you ever get flash chips
with more than 2^30 erase blocks, but even with the lowest known erase
granularity of 256 bytes, these flash chips will have to have a size of
a quarter Terabyte. I'm pretty confident we won't see such big EEPROMs
in the near future (or at least not attached in a way that makes
flashrom usable). For SPI chips, we even have a guaranteed safety factor
of 4096 over the maximum SPI chip size (which is 2^24). And if such a
big flash chip has uniform erase block size, you could even split it
among the 4 array members. If you change int count to unsigned int
count, the storable size doubles. So with a split and a slight change of
data type, the maximum ROM chip size is 2 Terabytes.

Since many chips have multiple block erase functions where the
eraseblock layout depends on the block erase function, this patch
couples the block erase functions with their eraseblock layouts.
struct block_eraser {
  struct eraseblock{
    unsigned int size; /* Eraseblock size */
    unsigned int count; /* Number of contiguous blocks with that size */
  } eraseblocks[NUM_ERASEREGIONS];
  int (*block_erase) (struct flashchip *flash, unsigned int blockaddr, unsigned int blocklen);
} block_erasers[NUM_ERASEFUNCTIONS];

Corresponding to flashrom svn r719.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Stefan Reinauer <stepan@coresystems.de>