[PATCH 4/6] bloblist: expose 'expand_by' as an output argument

[Tom Rini]

On Wed, Jun 18, 2025 at 04:01:02PM -0400, Raymond Mao wrote:
> Hi Tom,
> 
> On Wed, 18 Jun 2025 at 13:40, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Wed, Jun 18, 2025 at 07:59:26AM -0700, Raymond Mao wrote:
> >
> > > Some advanced usecases of bloblist needs to know the actual bytes
> > > expanded or shrunk after blob resizing.
> > > For example, to support applying DT overlay from bloblist, firstly
> > > the FDT blob needs to be resized for potential size increasing after
> > > applying overlay. If the DT overlay blob is one of the following blobs
> > > of the FDT, its address will be shifted after FDT blob resizing.
> > > Thus, returning 'expand_by' helps the caller to get the shifted data
> > > pointer when it comes to get the overlay for applying.
> > >
> > > Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
> > [snip]
> > > @@ -337,6 +338,7 @@ void *bloblist_ensure(uint tag, int size);
> > >   */
> > >  int bloblist_ensure_size_ret(uint tag, int *sizep, void **blobp);
> > >
> > > +#if CONFIG_IS_ENABLED(BLOBLIST)
> > >  /**
> > >   * bloblist_resize() - resize a blob
> > >   *
> > > @@ -345,10 +347,17 @@ int bloblist_ensure_size_ret(uint tag, int *sizep, void **blobp);
> > >   *
> > >   * @tag:     Tag to add (enum bloblist_tag_t)
> > >   * @new_size:        New size of the blob (>0 to expand, <0 to contract)
> > > + * @expand_by:       Number of bytes actually expanded by (-ve to contract)
> > >   * Return: 0 if OK, -ENOSPC if the bloblist does not have enough space, -ENOENT
> > >   * if the tag is not found
> > >   */
> > > -int bloblist_resize(uint tag, int new_size);
> > > +int bloblist_resize(uint tag, int new_size, int *expand_by);
> > > +#else
> > > +static inline int bloblist_resize(uint tag, int new_size, int *expand_by)
> > > +{
> > > +     return -EPERM;
> > > +}
> > > +#endif
> >
> > Do we really need to be doing this if/else in the header? What's failing
> > otherwise, and can we not guard that with:
> > if (IS_ENABLED(CONFIG_BLOBLIST)) {
> >   ..
> > }
> > in the code?
> >
> This function is needed to be called in fdtdec, if it is not guarded
> in the header file, we have to guard it from all its callers to avoid
> linker error when BLOBLIST is not selected (In the future, there might
> be more than one caller).

Yeah, I think I'd like to add the if/else later if we need it rather
than preemptively.

-- 
Tom
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