[M] Change in flashrom[main]: libflashrom: Update the API for Logger Callback

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Dmitry Zhadinets.

Anastasia Klimchuk has posted comments on this change by Dmitry Zhadinets. ( https://review.coreboot.org/c/flashrom/+/86875?usp=email )

Change subject: libflashrom: Update the API for Logger Callback
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Patch Set 6:

(4 comments)

Patchset:

PS6: 
I have two small readability comments, otherwise the only question to decide is message size right?

File include/libflashrom.h:

https://review.coreboot.org/c/flashrom/+/86875/comment/475b5a75_6e689bb1?usp... :
PS4, Line 83:  *
> Hmmmm. The user does not affect this, but as you wish.

I was trying to find it, but I couldn't, but then I found the addition at `flashrom_set_progress_callback_v2` :) I was thinking to add it at `flashrom_set_log_callback_v2` (the new fn that you are adding)

File libflashrom.c:

https://review.coreboot.org/c/flashrom/+/86875/comment/ad8d6a36_76bdf906?usp... :
PS4, Line 59: 	/* Dynamic messages and double formatting may not be ideal,
            : 	as they are slow. It would be better to limit the message
            : 	size to a fixed value (e.g., char message[1024] = {0};). */
> I would go shorter to perhaps 128 or 256 bytes, but have a fallback to dynamic allocation in case a  […]

I found one very long message in cli_classic.c, in `cli_classic_usage` (it prints help, as of `flashrom -h`), but I don't think it trigger a callback, since it's using printf directly?

This was the only very long message that I found. The rest probably fits into 256, but maybe let's do it 512 just in case?

Also 100% agree let's not drop long messages silently.
Actually if we don't drop than 256 is fine

File libflashrom.c:

https://review.coreboot.org/c/flashrom/+/86875/comment/f4f4b00f_02493a53?usp... :
PS6, Line 84: 	if (!log_callback && global_log_callback == format_message_and_invoke_log_callback_v2)
            : 		global_log_callback = NULL;
I spent some time looking at this, then I figured this is doing a reset (when log_callback is passed NULL).
It is possible to understand, but I have a suggestion to change this a bit, to make it more readable (more obvious).

What if you check if log_callback is NULL, and then assign all 3 values to NULL? and with 1-line comment like "Reset all callbacks since NULL is passed"

I know this code works already, my comment is only about readability.

```
if (!log_callback) {
   /* Reset all callbacks because NULL is passed */
   global_log_callback = NULL;
   global_log_callback_v2 = NULL;
   global_log_user_data = NULL;
} else {
.... and the rest as normal flow
}
```