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Date: Wed, 16 Jun 2010 07:30:21 +0300
From: Gleb Natapov <gleb@redhat.com>
Message-ID: <20100616043021.GE13238@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH] Fix comparison which always returned false
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: Anthony Liguori <aliguori@us.ibm.com>, QEMU Developers <qemu-devel@nongnu.org>

On Tue, Jun 15, 2010 at 11:28:42PM +0200, Jan Kiszka wrote:
> Stefan Weil wrote:
> > Comparing an 8 bit value with ~0 does not work as expected.
> > Replace ~0 by UINT8_MAX in comparison and also in assignment
> > (and fix coding style, too).
> > 
> > Cc: Gleb Natapov <gleb@redhat.com>
> > Cc: Anthony Liguori <aliguori@us.ibm.com>
> > Signed-off-by: Stefan Weil <weil@mail.berlios.de>
> > ---
> >  hw/hpet.c |    6 ++++--
> >  1 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/hpet.c b/hw/hpet.c
> > index 0c80ee5..d5c406c 100644
> > --- a/hw/hpet.c
> > +++ b/hw/hpet.c
> > @@ -74,7 +74,7 @@ typedef struct HPETState {
> >      uint8_t  hpet_id;           /* instance id */
> >  } HPETState;
> >  
> > -struct hpet_fw_config hpet_cfg = {.count = ~0};
> > +struct hpet_fw_config hpet_cfg = {.count = UINT8_MAX};
> >  
> >  static uint32_t hpet_in_legacy_mode(HPETState *s)
> >  {
> > @@ -682,8 +682,10 @@ static int hpet_init(SysBusDevice *dev)
> >      int i, iomemtype;
> >      HPETTimer *timer;
> >  
> > -    if (hpet_cfg.count == ~0) /* first instance */
> > +    if (hpet_cfg.count == UINT8_MAX) {
> > +        /* first instance */
> >          hpet_cfg.count = 0;
> > +    }
> >  
> >      if (hpet_cfg.count == 8) {
> >          fprintf(stderr, "Only 8 instances of HPET is allowed\n");
> 
> That makes me wonder why we need to signal this special value of
> hpet_cfg.count to seabios at all. Why isn't plain 0 for no hpets
> sufficient, Gleb?
> 
> Jan
> 
I want bios to be able to distinguish between qemu that does not support
HPET cfg_fw and qemu that does. On the former bios should always create
HPET table for backwards compatibility.

--
			Gleb.