Re: [Qemu-devel] [PATCHv8 1/3] fw_cfg: switch fw_cfg_find() to locate the fw_cfg device by type rather than path

[Michael S. Tsirkin]

On Tue, Jul 11, 2017 at 05:10:59PM -0300, Eduardo Habkost wrote:
> On Tue, Jul 11, 2017 at 09:02:11PM +0100, Mark Cave-Ayland wrote:
> > This will enable the fw_cfg device to be placed anywhere within the QOM tree
> > regardless of its machine location.
> > 
> > Note that we also add a comment to document the behaviour that we return 
> > NULL to
> > indicate failure where either no fw_cfg device or multiple fw_cfg devices 
> > are
> > found.
> > 
> > Signed-off-by: Mark Cave-Ayland <address@hidden>
> > ---
> >  hw/nvram/fw_cfg.c |    7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> > index 99bdbc2..8ef889a 100644
> > --- a/hw/nvram/fw_cfg.c
> > +++ b/hw/nvram/fw_cfg.c
> > @@ -1017,7 +1017,12 @@ FWCfgState *fw_cfg_init_mem(hwaddr ctl_addr, hwaddr 
> > data_addr)
> >  
> >  FWCfgState *fw_cfg_find(void)
> >  {
> > -    return FW_CFG(object_resolve_path(FW_CFG_PATH, NULL));
> > +    /* Returns FWCfgState if only one fw_cfg device type exists. If zero or
> > +       more than one fw_cfg device are found then NULL is returned as per 
> > the
> > +       object_resolve_path_type() documentation. This behaviour is correct 
> > as
> > +       it ensures that we detect both missing fw_cfg devices and multiple
> > +       fw_cfg devices which could result in unpredictable behaviour. */
> > +    return FW_CFG(object_resolve_path_type("", TYPE_FW_CFG, NULL));
> >  }
> 
> I believe a one-line "returns NULL unless there is exactly one
> fw_cfg device" (similar to the one at find_vmgenid_dev()) would
> suffice.  :)

Multi-line comments also should formatted

/*
 * like
 * this
 */

not

/* like
 * this */

> -- 
> Eduardo