Re: [Qemu-devel] [PATCH 2/2] tpm_tis: Return 0 for every register in case of failure mode

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 12/13/2017 05:26 AM, Marc-André Lureau wrote:
> Hi Stefan
>
> On Sat, Nov 11, 2017 at 4:39 AM, Stefan Berger
> <stefanb@linux.vnet.ibm.com> wrote:
>> Rather than returning ~0, return 0 for every register in case of
>> failure mode. The '0' is better to indicate that there's no device
>> there.
>>
>> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
>> ---
>>   hw/tpm/tpm_tis.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/tpm/tpm_tis.c b/hw/tpm/tpm_tis.c
>> index eca3374..d0bdd96 100644
>> --- a/hw/tpm/tpm_tis.c
>> +++ b/hw/tpm/tpm_tis.c
>> @@ -519,7 +519,7 @@ static uint64_t tpm_tis_mmio_read(void *opaque, hwaddr addr,
>>       uint8_t v;
>>
>>       if (tpm_backend_had_startup_error(s->be_driver)) {
>> -        return val;
>> +        return 0;
>>       }
> it's not obvious to me why it's better. Could you detail a bit more the reason?
>
> why not change the initialization of val instead?

http://patchwork.ozlabs.org/patch/838042/