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Re: [Qemu-devel] [PATCH v7 03/12] register: Add Memory API glue


From: Alistair Francis
Subject: Re: [Qemu-devel] [PATCH v7 03/12] register: Add Memory API glue
Date: Thu, 23 Jun 2016 09:30:39 -0700

On Thu, Jun 23, 2016 at 5:21 AM, Peter Maydell <address@hidden> wrote:
> On 22 June 2016 at 21:23, Alistair Francis <address@hidden> wrote:
>> Add memory io handlers that glue the register API to the memory API.
>> Just translation functions at this stage. Although it does allow for
>> devices to be created without all-in-one mmio r/w handlers.
>>
>> This patch also adds the RegisterInfoArray struct, which allows all of
>> the individual RegisterInfo structs to be grouped into a single memory
>> region.
>>
>> Signed-off-by: Peter Crosthwaite <address@hidden>
>> Signed-off-by: Alistair Francis <address@hidden>
>> ---
>> V7:
>>  - Remove endianess handling
>>  - Remove assert() and log missing registers
>> V6:
>>  - Add the memory region later
>> V5:
>>  - Convert to using only one memory region
>>
>>  hw/core/register.c    | 58 
>> +++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/hw/register.h | 43 ++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 101 insertions(+)
>>
>> diff --git a/hw/core/register.c b/hw/core/register.c
>> index cc067f1..149aebb 100644
>> --- a/hw/core/register.c
>> +++ b/hw/core/register.c
>> @@ -154,3 +154,61 @@ void register_reset(RegisterInfo *reg)
>>
>>      register_write_val(reg, reg->access->reset);
>>  }
>> +
>> +void register_write_memory(void *opaque, hwaddr addr,
>> +                           uint64_t value, unsigned size)
>> +{
>> +    RegisterInfoArray *reg_array = opaque;
>> +    RegisterInfo *reg = NULL;
>> +    uint64_t we = ~0;
>
> Really ~0 and not ~0ULL ? In any case this shouldn't need
> initializing as we will always set it later.
>
>> +    int i;
>> +
>> +    for (i = 0; i < reg_array->num_elements; i++) {
>> +        if (reg_array->r[i]->access->addr == addr) {
>> +            reg = reg_array->r[i];
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (!reg) {
>> +        qemu_log_mask(LOG_UNIMP, "Write to unimplemented register at " \
>> +                      "address: %#" PRIx64 "\n", addr);
>
> Shouldn't this be a LOG_GUEST_ERROR ?
>
>> +        return;
>> +    }
>> +
>> +    /* Generate appropriate write enable mask */
>> +    if (reg->data_size < size) {
>> +        we = MAKE_64BIT_MASK(0, reg->data_size * 8);
>> +    } else if (reg->data_size >= size) {
>
> Why not just "else {" ?
>
>> +        we = MAKE_64BIT_MASK(0, size * 8);
>> +    }
>> +
>> +    register_write(reg, value, we, reg_array->prefix,
>> +                   reg_array->debug);
>> +}
>> +
>> +uint64_t register_read_memory(void *opaque, hwaddr addr,
>> +                              unsigned size)
>> +{
>> +    RegisterInfoArray *reg_array = opaque;
>> +    RegisterInfo *reg = NULL;
>> +    uint64_t read_val;
>> +    int i;
>> +
>> +    for (i = 0; i < reg_array->num_elements; i++) {
>> +        if (reg_array->r[i]->access->addr == addr) {
>> +            reg = reg_array->r[i];
>> +            break;
>> +        }
>> +    }
>> +
>> +    if (!reg) {
>> +        qemu_log_mask(LOG_UNIMP, "Read to unimplemented register at " \
>> +                      "address: %#" PRIx64 "\n", addr);
>> +        return 0;
>> +    }
>> +
>> +    read_val = register_read(reg, reg_array->prefix, reg_array->debug);
>
> This will silently affect bits of the register outside the
> specified size with clear-on-read or other "reads have
> side effects" behaviour, which isn't consistent with how
> we handle writes.
>
>>  /**
>> + * This structure is used to group all of the individual registers which are
>> + * modeled using the RegisterInfo strucutre.
>
> "structure"

Fixed all.

Thanks,

Alistair

>
>> + *
>> + * @r is an aray containing of all the relevent RegisterInfo structures.
>> + *
>> + * @num_elements is the number of elements in the array r
>> + *
>> + * @mem: optional Memory region for the register
>> + */
>> +
>> +struct RegisterInfoArray {
>> +    int num_elements;
>> +    RegisterInfo **r;
>> +
>> +    bool debug;
>> +    const char *prefix;
>> +};
>> +
>
> thanks
> -- PMM
>



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