Re: [PATCH 1/2] lib/string_helpers: drop redundant allocation in kasprintf_strarray

[Thorsten Blum <thorsten.blum@linux.dev>]

On Wed, Apr 15, 2026 at 05:42:41PM +0300, Andy Shevchenko wrote:
> On Wed, Apr 15, 2026 at 02:25:43PM +0200, Thorsten Blum wrote:
> > kasprintf_strarray() returns an array of N strings and kfree_strarray()
> > also frees N entries.  However, kasprintf_strarray() currently allocates
> > N+1 char pointers.  Allocate exactly N pointers instead of N+1.
> > 
> > Also update the kernel-doc for @n.
> 
> Have you checked all current users that they do not rely on the NULL terminated
> array?

Yes, I've checked all call sites, and none of them rely on the NULL
terminator. Specifically, I checked:

  drivers/gpio/gpio-mockup.c

which uses PROPERTY_ENTRY_STRING_ARRAY_LEN(), and

  drivers/pinctrl/bcm/pinctrl-bcm4908.c
  drivers/pinctrl/intel/pinctrl-intel-platform.c
  drivers/pinctrl/meson/pinctrl-amlogic-a4.c
  drivers/pinctrl/mvebu/pinctrl-armada-37xx.c
  drivers/pinctrl/pinctrl-at91.c
  drivers/pinctrl/pinctrl-rockchip.c
  drivers/pinctrl/pinctrl-st.c

all of which use the size N to iterate over the returned array.

Also, kfree_strarray() explicitly takes the number of entries N,
indicating that callers are expected to keep track of it.

> Note, that was done on purpose that once allocated it can allow user
> to drop the track of the number of strings and rely on NULL terminator.
> I.o.w.  the number of strings may be just a local variable somewhere
> where kasprintf_strarray() is called.
> 
> I tend to NAK this change, rather you can update kernel-doc to explain
> why it's done this way (see above).