[PATCH] xyzModem: Correct xmodem blk verification conditions

[Tom Rini]

On Tue, Feb 06, 2024 at 09:05:33PM +0800, jihongbin wrote:

> It may be that there are relatively few people using this function, or the
> length of the transmitted data is less than 128byte * 255 byte, so the
> triggering conditions for the above problems are not encountered;
> 
> I actually discovered this problem during testing. Continuous transmission
> always fails at block 255.
> 
> The following is the protocol's definition of blk cblk, cblk = 255 - blk
> The original content of the agreement
> (https://www.menie.org/georges/embedded/xmodem_specification.html) is as
> follows:
> -------- 3. MESSAGE BLOCK LEVEL PROTOCOL
> Each block of the transfer looks like:
> <SOH><blk #><255-blk #><--128 data bytes--><cksum>
> in which:
> <SOH> = 01 hex
> <blk #> = binary number, starts at 01 increments by 1, and
> wraps 0FFH to 00H (not to 01)
> <255-blk #> = blk # after going thru 8080 "CMA" instr, i.e.
> each bit complemented in the 8-bit block number.
> Formally, this is the "ones complement".
> 
> <cksum> = the sum of the data bytes only. Toss any carry.

Please repost the patch with these kind of details in the commit
message, thanks.

-- 
Tom
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