Re: [PATCH] mos6522: remove anh register

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/12/19 8:43 PM, Laurent Vivier wrote:
> Register addr 1 is defined as buffer A with handshake (vBufAH),
> register addr 15 is also defined as buffer A without handshake (vBufA).

Maybe add "IOW both addresses access the same register."

> 
> Linux kernel has a big "DON'T USE!" next to the register 1 addr
> definition (vBufAH), and only uses register 15 (vBufA).

I agree with David, the Linux reference is confusing. I'd omit it.

> 
> So remove the definition of 'anh' and use only 'a' (with VIA_REG_ANH and
> VIA_REG_A).
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>   hw/misc/mos6522.c         | 12 ++++--------
>   include/hw/misc/mos6522.h |  1 -
>   2 files changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/misc/mos6522.c b/hw/misc/mos6522.c
> index cecf0be59e..86ede4005c 100644
> --- a/hw/misc/mos6522.c
> +++ b/hw/misc/mos6522.c
> @@ -244,6 +244,7 @@ uint64_t mos6522_read(void *opaque, hwaddr addr, unsigned size)
>           val = s->b;
>           break;
>       case VIA_REG_A:

Maybe add:

        /* As we do not model handshake, fall through no handshake. */

> +    case VIA_REG_ANH:
>           val = s->a;
>           break;
>       case VIA_REG_DIRB:
> @@ -297,9 +298,7 @@ uint64_t mos6522_read(void *opaque, hwaddr addr, unsigned size)
>           val = s->ier | 0x80;
>           break;
>       default:
> -    case VIA_REG_ANH:
> -        val = s->anh;

Oops, default was buggy.

Maybe worth:

Fixes: 51f233ec92c

> -        break;
> +        g_assert_not_reached();
>       }
>   
>       if (addr != VIA_REG_IFR || val != 0) {
> @@ -322,6 +321,7 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
>           mdc->portB_write(s);
>           break;
>       case VIA_REG_A:

        /* As we do not model handshake, fall through no handshake. */

> +    case VIA_REG_ANH:
>           s->a = (s->a & ~s->dira) | (val & s->dira);
>           mdc->portA_write(s);
>           break;
> @@ -395,9 +395,7 @@ void mos6522_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
>                                 qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
>           break;
>       default:
> -    case VIA_REG_ANH:
> -        s->anh = val;

Buggy again.

> -        break;
> +        g_assert_not_reached();
>       }
>   }
>   
> @@ -439,7 +437,6 @@ const VMStateDescription vmstate_mos6522 = {
>           VMSTATE_UINT8(pcr, MOS6522State),
>           VMSTATE_UINT8(ifr, MOS6522State),
>           VMSTATE_UINT8(ier, MOS6522State),
> -        VMSTATE_UINT8(anh, MOS6522State),

Don't you need to increase .version_id?

>           VMSTATE_STRUCT_ARRAY(timers, MOS6522State, 2, 0,
>                                vmstate_mos6522_timer, MOS6522Timer),
>           VMSTATE_END_OF_LIST()
> @@ -460,7 +457,6 @@ static void mos6522_reset(DeviceState *dev)
>       s->ifr = 0;
>       s->ier = 0;
>       /* s->ier = T1_INT | SR_INT; */
> -    s->anh = 0;
>   
>       s->timers[0].frequency = s->frequency;
>       s->timers[0].latch = 0xffff;
> diff --git a/include/hw/misc/mos6522.h b/include/hw/misc/mos6522.h
> index 493c907537..97384c6e02 100644
> --- a/include/hw/misc/mos6522.h
> +++ b/include/hw/misc/mos6522.h
> @@ -115,7 +115,6 @@ typedef struct MOS6522State {
>       uint8_t pcr;
>       uint8_t ifr;
>       uint8_t ier;
> -    uint8_t anh;
>   
>       MOS6522Timer timers[2];
>       uint64_t frequency;
>