[PATCH v2 04/12] sysinfo: Make sysinfo_get_str() behave like snprintf()

[Marek Behún]

On Thu, 4 Nov 2021 20:02:25 -0600
Simon Glass <sjg at chromium.org> wrote:

> Hi Marek,
> 
> On Wed, 3 Nov 2021 at 17:23, Marek Behún <kabel at kernel.org> wrote:
> >
> > From: Marek Behún <marek.behun at nic.cz>
> >
> > Currently sysinfo_get_str() returns 0 if a string is filled in the
> > given buffer, and otherwise gives no simple mechanism to determine
> > actual string length.
> >
> > One implementation returns -ENOSPC if buffer is not large enough.
> >
> > Change the behaviour of the function to that of snprintf(): i.e. the
> > buffer is always filled in as much as possible if the string exists, and
> > the function returns the actual length of the string (excluding the
> > terminating NULL-byte).
> >
> > Signed-off-by: Marek Behún <marek.behun at nic.cz>
> > ---
> >  board/google/chromebook_coral/coral.c | 13 ++++---------
> >  common/board_info.c                   |  2 +-
> >  drivers/sysinfo/gpio.c                |  2 +-
> >  drivers/sysinfo/rcar3.c               |  2 +-
> >  drivers/sysinfo/sandbox.c             |  5 +++--
> >  include/sysinfo.h                     | 16 ++++++++++++----
> >  lib/smbios.c                          |  2 +-
> >  test/dm/sysinfo-gpio.c                | 12 ++++++------
> >  test/dm/sysinfo.c                     | 12 ++++++------
> >  9 files changed, 35 insertions(+), 31 deletions(-)  
> 
> So how do we know if the size is too small? The string is silently truncated?

The same way as in snprintf.
If the return value is >= size, then size is too small.
(The return value is the length of the whole string (excluding \0 at
end), not just the part that was copied to buffer.)

Marek