Re: [Qemu-devel] [PATCH 3/8] fdc: Introduce fdctrl->phase

[Peter Maydell]

On 19 May 2015 at 16:35, Kevin Wolf <address@hidden> wrote:
> The floppy controller spec describes three different controller phases,
> which are currently not explicitly modelled in our emulation. Instead,
> each phase is represented by a combination of flags in registers.
>
> This patch makes explicit in which phase the controller currently is.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>  hw/block/fdc.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/hw/block/fdc.c b/hw/block/fdc.c
> index 8c41434..4d4868e 100644
> --- a/hw/block/fdc.c
> +++ b/hw/block/fdc.c
> @@ -495,6 +495,30 @@ enum {
>      FD_DIR_DSKCHG   = 0x80,
>  };
>
> +/*
> + * See chapter 5.0 "Controller phases" of the spec:
> + *
> + * Command phase:
> + * The host writes a command and its parameters into the FIFO. The command
> + * phase is completed when all parameters for the command have been supplied,
> + * and execution phase is entered.
> + *
> + * Execution phase:
> + * Data transfers, either DMA or non-DMA. For non-DMA transfers, the FIFO
> + * contains the payload now, otherwise it's unused. When all bytes of the
> + * required data have been transferred, the state is switched to either 
> result
> + * phase (if the command produces status bytes) or directly back into the
> + * command phase for the next command.
> + *
> + * Result phase:
> + * The host reads out the FIFO, which contains one or more result bytes now.
> + */
> +typedef enum FDCtrlPhase {
> +    FD_PHASE_COMMAND,
> +    FD_PHASE_EXECUTION,
> +    FD_PHASE_RESULT,
> +} FDCtrlPhase;
> +
>  #define FD_MULTI_TRACK(state) ((state) & FD_STATE_MULTI)
>  #define FD_FORMAT_CMD(state) ((state) & FD_STATE_FORMAT)
>
> @@ -504,6 +528,7 @@ struct FDCtrl {
>      /* Controller state */
>      QEMUTimer *result_timer;
>      int dma_chann;
> +    FDCtrlPhase phase;

This is new state -- don't we need to handle it on migration?

In general I'm not a huge fan of caching derived state in
device models...

-- PMM