Re: [PATCH v3 07/12] libfdt: Add fdt_setprop_inplace_by_index

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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On Mon, Jun 27, 2016 at 01:45:11AM +1000, David Gibson wrote:
> On Fri, Jun 24, 2016 at 04:27:52PM +0200, Maxime Ripard wrote:
> > Add a function to modify inplace a property starting from a given index.
> > 
> > This is especially useful when the property is an array of values, and you
> > want to update one of them without changing the DT size.
> > 
> > Signed-off-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> > ---
> >  include/libfdt.h     | 34 +++++++++++++++++++++++++++++++---
> >  lib/libfdt/fdt_wip.c | 13 ++++++++-----
> >  2 files changed, 39 insertions(+), 8 deletions(-)
> > 
> > diff --git a/include/libfdt.h b/include/libfdt.h
> > index 4643be5adf39..2c8a42bcb667 100644
> > --- a/include/libfdt.h
> > +++ b/include/libfdt.h
> > @@ -1032,6 +1032,27 @@ int fdt_size_cells(const void *fdt, int nodeoffset);
> >  /* Write-in-place functions                                           */
> >  /**********************************************************************/
> >  
> > +/**
> > + * fdt_setprop_inplace_namelen_by_index - change a property's value,
> > + *                                        but not its size
> > + * @fdt: pointer to the device tree blob
> > + * @nodeoffset: offset of the node whose property to change
> > + * @name: name of the property to change
> > + * @namelen: number of characters of name to consider
> > + * @index: index of the property to change in the array
> > + * @val: pointer to data to replace the property value with
> > + * @len: length of the property value
> > + *
> > + * Identical to fdt_setprop_inplace(), but modifies the given property
> > + * starting from the given index, and using only the first characters
> > + * of the name. It is useful when you want to manipulate only one value of
> > + * an array and you have a string that doesn't end with \0.
> > + */
> > +int fdt_setprop_inplace_namelen_by_index(void *fdt, int nodeoffset,
> > +					 const char *name, int namelen,
> > +					 uint32_t index, const void *val,
> > +					 int len);
> 
> This looks like a good addition to upstream, but I don't like the
> name.  I'd suggest fdt_setprop_inplace_namelen_partial() because it
> only overwrite part of the existing property value.

Ack.

> > +
> >  /**
> >   * fdt_setprop_inplace - change a property's value, but not its size
> >   * @fdt: pointer to the device tree blob
> > @@ -1060,8 +1081,13 @@ int fdt_size_cells(const void *fdt, int nodeoffset);
> >   *	-FDT_ERR_BADSTRUCTURE,
> >   *	-FDT_ERR_TRUNCATED, standard meanings
> >   */
> > -int fdt_setprop_inplace(void *fdt, int nodeoffset, const char *name,
> > -			const void *val, int len);
> > +static inline int fdt_setprop_inplace(void *fdt, int nodeoffset,
> > +				      const char *name, const void *val,
> > +				      int len)
> > +{
> > +	return fdt_setprop_inplace_namelen_by_index(fdt, nodeoffset, name,
> > +						    strlen(name), 0, val, len);
> 
> This effectively removes the error if len is not equal to the existing
> property length, so that needs to be put back.

So I'm not really sure what you want me to do.

I can't check for the property length, since it would prevent that
function from working, I can't check for the length + index, since we
might update only a few bytes in the middle, and we want to keep that
error case.

Or should I just forgive about merging the two functions and just
duplicate the two?

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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