Re: [PATCH v2 4/5] zram: add per-backend caps and validate parameters early

[haoqin huang]

On Wed, Jul 29, 2026 at 10:26 AM Sergey Senozhatsky
<senozhatsky@xxxxxxxxxxxx> wrote:
>
> On (26/07/28 17:29), Haoqin Huang wrote:
> [..]
> > +unsigned int zcomp_get_caps(const char *comp)
> > +{
> > +     const struct zcomp_ops *backend = lookup_backend_ops(comp);
> > +
> > +     return backend ? backend->caps : 0;
> > +}
> > +
> > +int zcomp_validate_level(const char *comp, s32 level)
> > +{
> > +     const struct zcomp_ops *backend = lookup_backend_ops(comp);
> > +
> > +     if (!backend)
> > +             return -EINVAL;
> > +     if (!(backend->caps & ZCOMP_CAP_LEVEL))
> > +             return -EOPNOTSUPP;
> > +     if (level < backend->level_min || level > backend->level_max)
> > +             return -EINVAL;
> > +     return 0;
> > +}
>
> [..]
>
> > +unsigned int zcomp_get_caps(const char *comp);
> > +int zcomp_validate_level(const char *comp, s32 level);
>
> [..]
>
> > @@ -1796,6 +1796,25 @@ static ssize_t algorithm_params_store(struct device *dev,
> >                       return -EINVAL;
> >       }
> >
> > +     if (zram->comp_algs[prio]) {
> > +             unsigned int caps = zcomp_get_caps(zram->comp_algs[prio]);
> > +
> > +             if (dict_path && !(caps & ZCOMP_CAP_DICT)) {
> > +                     pr_err("zram: %s does not support dictionary\n",
> > +                            zram->comp_algs[prio]);
> > +                     return -EOPNOTSUPP;
> > +             }
> > +
> > +             if (level != ZCOMP_PARAM_NOT_SET) {
> > +                     ret = zcomp_validate_level(zram->comp_algs[prio], level);
> > +                     if (ret) {
> > +                             pr_err("zram: invalid level for %s\n",
> > +                                    zram->comp_algs[prio]);
> > +                             return ret;
> > +                     }
> > +             }
> > +     }
>
> So I wonder if instead of introducing 2 new zcomp functions (zcomp_get_caps()
> and zcomp_validate_level()) and still basically open-coding params verification
> in zram, maybe we we can just have one
>         int zcomp_validate_params(comp, level, dict_path)
> and handle all the validation in zcomp internally.  So that in
> algorithm_params_store() it will be just
>
>         ret = zcomp_validate_params(zram->comp_algs[prio], level, dict_path);
>         if (ret)
>                 return ret;

Sounds good, I'll merge them into a single zcomp_validate_params() in v3.