Re: [OSS-Tools] [PATCH v2] barebox-state: have the --set option to avoid writes if possible

[Roland Hieber <rhi@pengutronix.de>]

On Fri, Nov 13, 2020 at 08:08:56PM +0100, Ahmad Fatoum wrote:
> barebox-state --set always dirties the state when successful. Users
> seeking to conserve write cycles thus have to --get the variable in
> question first to check whether to write it. Make life of such users
> easier by having barebox-state support this out-of-the-box.
> 
> This allows users to fire and forget execute barebox-state.
> 
> This arguably should have been the behavior from the beginning,
> the state implementation shared by barebox and dt-utils already
> marks the state dirty if buckets appear corrupted on probe, so
> there is no extra benefit in always executing the write.
> 
> The comparison to determine whether the state should be dirtied
> does an extra allocation in interest of clarity.
> This overhead is deemed negligible compared to I/O and it makes
> the code easier to follow.
> 
> Suggested-by: Jan Lübbe <jlu@pengutronix.de>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
> v1 -> v2:
>   - incorporate Jan's (off-list) suggestion to just change --set
>     behavior. state implementation already dirties state if a
>     bucket is corrupt, so there is really no valid use case for
>     not conserving writes by default.
> ---
>  src/barebox-state.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

Thanks, applied.

 - Roland

> 
> diff --git a/src/barebox-state.c b/src/barebox-state.c
> index cd56ce7192c3..7b5c0dae00dd 100644
> --- a/src/barebox-state.c
> +++ b/src/barebox-state.c
> @@ -283,6 +283,7 @@ static int state_set_var(struct state *state, const char *var, const char *val)
>  {
>  	struct state_variable *sv;
>  	struct variable_str_type *vtype;
> +	char *oldval;
>  	int ret;
>  
>  	sv = state_find_var(state, var);
> @@ -296,6 +297,14 @@ static int state_set_var(struct state *state, const char *var, const char *val)
>  	if (!vtype->set)
>  		return -EPERM;
>  
> +	oldval = vtype->get(sv);
> +	if (!IS_ERR(oldval)) {
> +		bool equal = strcmp(oldval, val) == 0;
> +		free(oldval);
> +		if (equal)
> +			return 0;
> +	}
> +
>  	ret = vtype->set(sv, val);
>  	if (ret)
>  		return ret;
> -- 
> 2.28.0
> 
> 
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> OSS-Tools@pengutronix.de

-- 
Roland Hieber, Pengutronix e.K.          | r.hieber@pengutronix.de     |
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