Re: [PATCH v3 1/2] printk: console: Create console= parser that supports named options

Chris Down
2023-04-17T15:04:36Z

(To others on this thread wondering about this patchset, Petr and I have had
some discussions offlist about v4 and it should be up soon.)

Petr Mladek writes:
>I thought a lot how to do it a clean way. IMHO, it would be great to
>parse everything at a single place but it might require updating
>all drivers. I am not sure if it is worth it.
>
>So, I suggest to do it another way. We could implement a generic
>function to find in the new key[:value] format. It would check
>if the given option (key) exists and read the optional value.
>
>The optional value would allow to define another new options
>that would not need any value, e.g. "kthread" or "atomic" that
>might be used in the upcoming code that allows to offload
>console handling to kthreads.

Any thoughts on something simple like this that takes advantage of memmove()?
This should overcome the mmio/io concerns, and it's fairly simple.

---

static bool find_and_remove_console_option(char *buf, size_t size,
const char *wanted, char *options)
{
bool found = false, first = true;
char *item, *opt = options;

while ((item = strsep(&opt, ","))) {
char *key = item, *value;

value = strchr(item, ':');
if (value)
*(value++) = '\0';

if (strcmp(key, wanted) == 0) {
found = true;
if (value) {
if (strlen(value) > size - 1) {
pr_warn("Can't copy console option value for %s:%s: not enough space (%zu)\n",
key, value, size);
found = false;
} else {
strscpy(buf, value, size);
}
} else
*buf = '\0';
}

if (!found && opt)
*(opt - 1) = ',';
if (!found && value)
*(value - 1) = ':';
if (!first)
*(item - 1) = ',';

if (found)
break;

first = false;
}

if (found) {
if (opt)
memmove(item, opt, strlen(opt) + 1);
else if (first)
*item = '\0';
else
*--item = '\0';
}

return found;
}