Re: [Qemu-devel] [PATCH v4 07/17] spapr_rtas: add ibm, configure-connector RTAS interface

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

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On Tue, Dec 23, 2014 at 06:30:21AM -0600, Michael Roth wrote:

This really wants a commit message explaining in outline what
configure_connector does.

> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr_rtas.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 81 insertions(+)
> 
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 13e6e55..d847f45 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -422,6 +422,85 @@ static void rtas_get_sensor_state(PowerPCCPU *cpu, sPAPREnvironment *spapr,
>      rtas_st(rets, 1, entity_sense);
>  }
>  
> +/* configure-connector work area offsets, int32_t units for field
> + * indexes, bytes for field offset/len values.
> + *
> + * as documented by PAPR+ v2.7, 13.5.3.5
> + */
> +#define CC_IDX_NODE_NAME_OFFSET 2
> +#define CC_IDX_PROP_NAME_OFFSET 2
> +#define CC_IDX_PROP_LEN 3
> +#define CC_IDX_PROP_DATA_OFFSET 4
> +#define CC_VAL_DATA_OFFSET ((CC_IDX_PROP_DATA_OFFSET + 1) * 4)
> +#define CC_WA_LEN 4096

Any reason not to use a struct for this?

> +
> +static void rtas_ibm_configure_connector(PowerPCCPU *cpu,
> +                                         sPAPREnvironment *spapr,
> +                                         uint32_t token, uint32_t nargs,
> +                                         target_ulong args, uint32_t nret,
> +                                         target_ulong rets)
> +{

As always, you need to validate nargs and nret first.

> +    uint64_t wa_addr = ((uint64_t)rtas_ld(args, 1) << 32) | rtas_ld(args, 0);
> +    uint64_t wa_offset;
> +    uint32_t drc_index;
> +    sPAPRDRConnector *drc;
> +    sPAPRDRConnectorClass *drck;
> +    sPAPRDRCCResponse resp;
> +    const struct fdt_property *prop = NULL;
> +    char *prop_name = NULL;
> +    int prop_len, rc;
> +
> +    drc_index = rtas_ld(wa_addr, 0);

I'm trying to work out if this is an abuse of the rtas_ld interface.
As written it wasn't intended for accessing anything other than the
immediate rtas args and return values.

> +    drc = spapr_dr_connector_by_index(drc_index);
> +    if (!drc) {
> +        DPRINTF("rtas_ibm_configure_connector: invalid sensor/DRC index: %xh\n",
> +                drc_index);
> +        rc = RTAS_OUT_PARAM_ERROR;
> +        goto out;
> +    }
> +    drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> +    resp = drck->configure_connector(drc, &prop_name, &prop, &prop_len);

So, the RTAS interface is stuck with the rather clunky iteration
through the device tree.  But I don't see a good reason to replicate
that clunky interface for communication between the DR core and the
individual connector drivers.

Wouldn't it make more sense for the class callback to just return the
fdt fragment, and then do all the iteration in the DR core?

> +    switch (resp) {
> +    case SPAPR_DR_CC_RESPONSE_NEXT_CHILD:
> +        /* provide the name of the next OF node */
> +        wa_offset = CC_VAL_DATA_OFFSET;
> +        rtas_st(wa_addr, CC_IDX_NODE_NAME_OFFSET, wa_offset);
> +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> +                              (uint8_t *)prop_name, strlen(prop_name) + 1);
> +        break;
> +    case SPAPR_DR_CC_RESPONSE_NEXT_PROPERTY:
> +        /* provide the name of the next OF property */
> +        wa_offset = CC_VAL_DATA_OFFSET;
> +        rtas_st(wa_addr, CC_IDX_PROP_NAME_OFFSET, wa_offset);
> +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> +                              (uint8_t *)prop_name, strlen(prop_name) + 1);
> +
> +        /* provide the length and value of the OF property. data gets placed
> +         * immediately after NULL terminator of the OF property's name string
> +         */
> +        wa_offset += strlen(prop_name) + 1,
> +        rtas_st(wa_addr, CC_IDX_PROP_LEN, prop_len);
> +        rtas_st(wa_addr, CC_IDX_PROP_DATA_OFFSET, wa_offset);
> +        rtas_st_buffer_direct(wa_addr + wa_offset, CC_WA_LEN - wa_offset,
> +                              (uint8_t *)((struct fdt_property *)prop)->data,
> +                              prop_len);
> +        break;
> +    case SPAPR_DR_CC_RESPONSE_PREV_PARENT:
> +    case SPAPR_DR_CC_RESPONSE_ERROR:
> +    case SPAPR_DR_CC_RESPONSE_SUCCESS:
> +        break;
> +    default:
> +        /* drck->configure_connector() should not return anything else */
> +        g_assert(false);
> +    }
> +
> +    rc = resp;
> +out:
> +    g_free(prop_name);
> +    rtas_st(rets, 0, rc);
> +}
> +
>  static struct rtas_call {
>      const char *name;
>      spapr_rtas_fn fn;
> @@ -559,6 +638,8 @@ static void core_rtas_register_types(void)
>                          rtas_set_indicator);
>      spapr_rtas_register(RTAS_GET_SENSOR_STATE, "get-sensor-state",
>                          rtas_get_sensor_state);
> +    spapr_rtas_register(RTAS_IBM_CONFIGURE_CONNECTOR, "ibm,configure-connector",
> +                        rtas_ibm_configure_connector);
>  }
>  
>  type_init(core_rtas_register_types)

-- 
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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