Re: [Qemu-devel] [PATCH 6/7] mac_dbdma: change DBDMA_register_channel to a MAC_DBDMA type method

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Sep 24, 2017 at 03:47:45PM +0100, Mark Cave-Ayland wrote:
> Using this we can change the MACIO_IDE instance to register the channel
> itself via a type method instead of requiring a separate
> DBDMA_register_channel() function.
> 
> As a consequence of this it is now possible to remove the old external
> macio_ide_register_dma() function.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

Ok, two concerns about this.

First, you've added the function pointer to the instance, not to the
class, which is not how a QOM method would normally be done.

More generally, though, why is a method preferable to a plain
function?  AFAICT it's not plausible that there will ever be more than
one implementation of the method.

Same comments apply to patch 7/7.

> ---
>  hw/ide/macio.c             |   12 ++++++------
>  hw/misc/macio/mac_dbdma.c  |    9 +++++----
>  hw/misc/macio/macio.c      |    1 -
>  include/hw/ppc/mac_dbdma.h |    9 ++++-----
>  4 files changed, 15 insertions(+), 16 deletions(-)
> 
> diff --git a/hw/ide/macio.c b/hw/ide/macio.c
> index ce194c6..b296017 100644
> --- a/hw/ide/macio.c
> +++ b/hw/ide/macio.c
> @@ -411,12 +411,18 @@ static const IDEDMAOps dbdma_ops = {
>  static void macio_ide_realizefn(DeviceState *dev, Error **errp)
>  {
>      MACIOIDEState *s = MACIO_IDE(dev);
> +    DBDMAState *dbdma;
>  
>      ide_init2(&s->bus, s->ide_irq);
>  
>      /* Register DMA callbacks */
>      s->dma.ops = &dbdma_ops;
>      s->bus.dma = &s->dma;
> +
> +    /* Register DBDMA channel */
> +    dbdma = MAC_DBDMA(object_property_get_link(OBJECT(dev), "dbdma", errp));
> +    dbdma->register_channel(dbdma, s->channel, s->dma_irq,
> +                            pmac_ide_transfer, pmac_ide_flush, s);
>  }
>  
>  static void pmac_ide_irq(void *opaque, int n, int level)
> @@ -497,10 +503,4 @@ void macio_ide_init_drives(MACIOIDEState *s, DriveInfo **hd_table)
>      }
>  }
>  
> -void macio_ide_register_dma(MACIOIDEState *s)
> -{
> -    DBDMA_register_channel(s->dbdma, s->channel, s->dma_irq,
> -                           pmac_ide_transfer, pmac_ide_flush, s);
> -}
> -
>  type_init(macio_ide_register_types)
> diff --git a/hw/misc/macio/mac_dbdma.c b/hw/misc/macio/mac_dbdma.c
> index 0eddf2e..addb97d 100644
> --- a/hw/misc/macio/mac_dbdma.c
> +++ b/hw/misc/macio/mac_dbdma.c
> @@ -557,11 +557,10 @@ void DBDMA_kick(DBDMAState *dbdma)
>      qemu_bh_schedule(dbdma->bh);
>  }
>  
> -void DBDMA_register_channel(void *dbdma, int nchan, qemu_irq irq,
> -                            DBDMA_rw rw, DBDMA_flush flush,
> -                            void *opaque)
> +static void
> +dbdma_register_channel(DBDMAState *s, int nchan, qemu_irq irq,
> +                       DBDMA_rw rw, DBDMA_flush flush, void *opaque)
>  {
> -    DBDMAState *s = dbdma;
>      DBDMA_channel *ch = &s->channels[nchan];
>  
>      DBDMA_DPRINTFCH(ch, "DBDMA_register_channel 0x%x\n", nchan);
> @@ -903,6 +902,8 @@ static void mac_dbdma_init(Object *obj)
>  
>      memory_region_init_io(&s->mem, obj, &dbdma_ops, s, "dbdma", 0x1000);
>      sysbus_init_mmio(sbd, &s->mem);
> +
> +    s->register_channel = dbdma_register_channel;
>  }
>  
>  static void mac_dbdma_realize(DeviceState *dev, Error **errp)
> diff --git a/hw/misc/macio/macio.c b/hw/misc/macio/macio.c
> index 9aa7e75..533331a 100644
> --- a/hw/misc/macio/macio.c
> +++ b/hw/misc/macio/macio.c
> @@ -161,7 +161,6 @@ static void macio_realize_ide(MacIOState *s, MACIOIDEState *ide,
>      sysbus_connect_irq(sysbus_dev, 1, irq1);
>      qdev_prop_set_uint32(DEVICE(ide), "channel", dmaid);
>      object_property_set_link(OBJECT(ide), OBJECT(s->dbdma), "dbdma", errp);
> -    macio_ide_register_dma(ide);
>  
>      object_property_set_bool(OBJECT(ide), true, "realized", errp);
>  }
> diff --git a/include/hw/ppc/mac_dbdma.h b/include/hw/ppc/mac_dbdma.h
> index 26cc469..d6a38c5 100644
> --- a/include/hw/ppc/mac_dbdma.h
> +++ b/include/hw/ppc/mac_dbdma.h
> @@ -160,19 +160,18 @@ typedef struct DBDMA_channel {
>      dbdma_cmd current;
>  } DBDMA_channel;
>  
> -typedef struct {
> +typedef struct DBDMAState {
>      SysBusDevice parent_obj;
>  
>      MemoryRegion mem;
>      DBDMA_channel channels[DBDMA_CHANNELS];
>      QEMUBH *bh;
> +
> +    void (*register_channel)(struct DBDMAState *s, int nchan, qemu_irq irq,
> +                             DBDMA_rw rw, DBDMA_flush flush, void *opaque);
>  } DBDMAState;
>  
>  /* Externally callable functions */
> -
> -void DBDMA_register_channel(void *dbdma, int nchan, qemu_irq irq,
> -                            DBDMA_rw rw, DBDMA_flush flush,
> -                            void *opaque);
>  void DBDMA_kick(DBDMAState *dbdma);
>  
>  #define TYPE_MAC_DBDMA "mac-dbdma"

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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