On Tue, 2 Sep 2008, Wolfgang Denk wrote:
- /* Offset inside a block */
- block_seek = offset - blockstart;
...
/* Limit to one block for the first read */Why?
Because this is on NAND, there we have to perform all IO block at a time.
/** If a block is bad, we retry in the next block at the same* offset - see common/env_nand.c::writeenv()*/lseek (fd, blockstart + block_seek, SEEK_SET);Hm... there was a "continue" for the badblock case just above, so do we really try the _next_ block here?
I meant, if the first block with non-zero offset (block_seek) was bad, then in the _next_ after it block we try at the same offset.
- /*
* Data size we actually have to write: from the start of the block* to the start of the data, then count bytes ob data, and to the-------------------------------------------------------^ f
* end of the block*/Hm... sounds as if this was always exactly one full block, then?
or two, or three...
- write_total = (block_seek + count + blocklen - 1) & ~(blocklen - 1);
- /*
* Support data anywhere within erase sectors: read out the complete* area to be erased, replace the environment image, write the whole* block back again.*/- if (write_total > count) {
data = malloc (erase_len);My understanding is, that erase_len can be > block size. Is this correct?
Yes.
I don't see where the actual size of the environment data is taken into considration?
in the "count" function parameter, which is then used to calculate write_total.
- } else {
/* Offset is block-aligned by construction here */What does "block-aligned by construction" mean?
It means, by the way I constructed (calculated) lengths above this place, we land here only if offset is block-aligned.
- erase.length = erasesize;
- /* This only runs once on NOR flash */
How comes that?
Because on NOR I set "erasesize" to the total length of the data plus alignment.
Thanks Guennadi --- Guennadi Liakhovetski, Ph.D.
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