Re: [PATCH 2/2] globalvar: add helpers for stashing global variables

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hello Sascha,

On 3/18/26 09:12, Sascha Hauer wrote:
> On Thu, Mar 12, 2026 at 03:43:16PM +0100, Ahmad Fatoum wrote:
>> Configuring a FIT image boot with overlays involves setting not only
>> global.bootm.* variables, but also global.of.overlay.* variables.
>>
>> For use in custom boot entry functions, provide functions for stashing
>> and restoring a set of variables. This allows dry run and boot fallback
>> behavior to not affect later boot attempts.
> 
> Looks generally good. I assume this is to replace the .dyn. type
> variables, right?

Not on its own, because there is no means to use this from scripts.
For the .dyn. case I was thinking about a locally scope bootm bobject
that can be modified in the boot script and then discarded afterwards.

> Can we the a user before applying this?

The single user on my side is out-of-tree board code that uses it scope
use of global.of.overlay.filter Here's an excerpt:

 LIST_HEAD(stash);

 globalvar_stash_push(stash, "of.overlay.pattern", "of.overlay.filter", 
                      "of.overlay.path", NULL);

 globalvar_set("of.overlay.path", kernel);                              
 globalvar_set("of.overlay.filter", "pattern");                         
 globalvar_set("of.overlay.pattern", pattern);                          

 ret = bootm_entry(entry, &bootm_data);

 globalvar_stash_pop(&stash);


Thanks,
Ahmad

> 
> Sascha
> 
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>>  common/globalvar.c  | 77 +++++++++++++++++++++++++++++++++++++++++++++
>>  include/globalvar.h |  3 ++
>>  2 files changed, 80 insertions(+)
>>
>> diff --git a/common/globalvar.c b/common/globalvar.c
>> index c2b0d5b4bbad..e168d6055347 100644
>> --- a/common/globalvar.c
>> +++ b/common/globalvar.c
>> @@ -461,6 +461,83 @@ int globalvar_set(const char *name, const char *val)
>>  	return dev_set_param(&global_device, name, val);
>>  }
>>  
>> +struct globalvar_stashed {
>> +	const char *key;
>> +	const char *value;
>> +	struct list_head list;
>> +};
>> +
>> +static void globalvar_stashed_free(struct globalvar_stashed *elem)
>> +{
>> +	list_del(&elem->list);
>> +	free_const(elem->key);
>> +	free_const(elem->value);
>> +	free(elem);
>> +}
>> +
>> +int globalvar_stash_push(struct list_head *stash, ...)
>> +{
>> +	struct globalvar_stashed *elem, *safe;
>> +	const char *name;
>> +	int ret = -ENOMEM;
>> +	va_list args;
>> +	LIST_HEAD(tmp);
>> +
>> +	va_start(args, stash);
>> +
>> +	while ((name = va_arg(args, const char *))) {
>> +		const char *value;
>> +
>> +		elem = calloc(1, sizeof(*elem));
>> +		if (!elem)
>> +			goto out;
>> +
>> +		list_add_tail(&elem->list, &tmp);
>> +
>> +		elem->key = strdup_const(name);
>> +		if (!elem->key)
>> +			goto out;
>> +
>> +		value = globalvar_get(name);
>> +		if (!value) {
>> +			ret = -EINVAL;
>> +			goto out;
>> +		}
>> +
>> +		elem->value = strdup_const(value);
>> +		if (!elem->value)
>> +			goto out;
>> +	}
>> +
>> +	list_splice_tail(&tmp, stash);
>> +
>> +	ret = 0;
>> +out:
>> +	va_end(args);
>> +
>> +	if (ret) {
>> +		list_for_each_entry_safe(elem, safe, &tmp, list)
>> +			globalvar_stashed_free(elem);
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +int globalvar_stash_pop(struct list_head *stash)
>> +{
>> +	struct globalvar_stashed *elem, *tmp;
>> +	int err = 0;
>> +
>> +	list_for_each_entry_safe(elem, tmp, stash, list) {
>> +		int ret = globalvar_set(elem->key, elem->value);
>> +		if (ret)
>> +			err = ret;
>> +		globalvar_stashed_free(elem);
>> +	}
>> +
>> +	return err;
>> +}
>> +
>>  static int globalvar_simple_set(struct bobject *bobj, struct param_d *p,
>>  				const char *val)
>>  {
>> diff --git a/include/globalvar.h b/include/globalvar.h
>> index 413cf72002a0..1d39849ddbab 100644
>> --- a/include/globalvar.h
>> +++ b/include/globalvar.h
>> @@ -24,6 +24,9 @@ char *globalvar_get_match(const char *match, const char *separator);
>>  void globalvar_set_match(const char *match, const char *val);
>>  int globalvar_set(const char *name, const char *val);
>>  
>> +int globalvar_stash_push(struct list_head *stash, ...) __attribute__((sentinel));
>> +int globalvar_stash_pop(struct list_head *stash);
>> +
>>  int globalvar_add_simple_string(const char *name, char **value);
>>  int globalvar_add_simple_int(const char *name, int *value,
>>  			     const char *format);
>> -- 
>> 2.47.3
>>
>>
>>
> 


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