Re: [Qemu-devel] [PATCH v2 2/8] ppc4xx_i2c: Move register state to private struct and remove unimplemented sdata and intr registers

[BALATON Zoltan]

On Fri, 8 Jun 2018, David Gibson wrote:
> On Wed, Jun 06, 2018 at 03:31:48PM +0200, BALATON Zoltan wrote:
> > Signed-off-by: BALATON Zoltan <address@hidden>
>
> It's not clear to me why this is preferable to having the registers
> embedded in the state structure.  The latter is pretty standard
> practice for qemu.

Maybe it will be clearer after the next patch in the series. I needed a 
place to store the bitbang_i2c_interface for the directcntl way of 
accessing the i2c bus but I can't include bitbang_i2c.h from the public 
header because it's a local header. So I needed a local extension to the 
state struct. Once I have that then it's a good place to also store 
private registers which are now defined in the same file so I don't have 
to look up them in a different place. This seemed clearer to me and easier 
to work with. Maybe the spliting of the rewrite did not make this clear.

One thing I'm not sure about though:

> > ---
> >  hw/i2c/ppc4xx_i2c.c         | 75 +++++++++++++++++++++++++--------------------
> >  include/hw/i2c/ppc4xx_i2c.h | 19 ++----------
> >  2 files changed, 43 insertions(+), 51 deletions(-)
> >
> > diff --git a/hw/i2c/ppc4xx_i2c.c b/hw/i2c/ppc4xx_i2c.c
> > index d1936db..a68b5f7 100644
> > --- a/hw/i2c/ppc4xx_i2c.c
> > +++ b/hw/i2c/ppc4xx_i2c.c
[...]
> > @@ -330,7 +335,9 @@ static const MemoryRegionOps ppc4xx_i2c_ops = {
> >  static void ppc4xx_i2c_init(Object *o)
> >  {
> >      PPC4xxI2CState *s = PPC4xx_I2C(o);
> > +    PPC4xxI2CRegs *r = g_malloc0(sizeof(PPC4xxI2CRegs));
> >
> > +    s->regs = r;
> >      memory_region_init_io(&s->iomem, OBJECT(s), &ppc4xx_i2c_ops, s,
> >                            TYPE_PPC4xx_I2C, PPC4xx_I2C_MEM_SIZE);
> >      sysbus_init_mmio(SYS_BUS_DEVICE(s), &s->iomem);

I allocate memory here but I'm not sure if it should be g_free'd somewhere 
and if so where? I was not able to detangle QOM object hierarchies and 
there seems to be no good docs available or I haven't found them. (PCI 
devices seem to have unrealize methods but this did not work for I2C 
objects.)