Change in flashrom[master]: buspirate_spi.c: Refactor singleton states into reentrant pattern

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Nico Huber, Edward O'Callaghan, Angel Pons.
Anastasia Klimchuk has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/52958 )

Change subject: buspirate_spi.c: Refactor singleton states into reentrant pattern
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Patch Set 2:

(1 comment)

File buspirate_spi.c:

https://review.coreboot.org/c/flashrom/+/52958/comment/a426863c_94757414 
PS2, Line 167: 	struct buspirate_spi_data *buspirate_data = data;
> How about an […]

Thank you for this comment, because I started resolving it and so spent some more time staring at the code. And I noticed something!
It looks to me that bp_commbuf does not have a global meaning, its value is rewritten for every send operation (and for shutdown as well). Specifically what I mean is for these functions:
1) buspirate_spi_shutdown
2) buspirate_spi_send_command_v1
3) buspirate_spi_send_command_v2
3) buspirate_spi_init
I can probably create bp_commbuf as a local variable, alloc at the beginning and free at the end.
bp_commbufsize is different, I can see why it needs to be in a spi data in flashctx.

buspirate_commbuf_grow and buspirate_sendrecv can take both as arguments.

What I am worried about is, maybe I am missing something? Why bp_commbuf was initally a global variable, was it just for convenience or for a reason?
What do you think?