[04/16] tpm: Clean up model registration & lookup

We have a strict separation between enum TpmModel and tpm_models[]:

* TpmModel may have any number of members.  It just happens to have one.

* tpm_register_model() uses the first empty slot in tmp_models[].

  If you register more than tpm_models[] has space,
  tpn_register_model() fails.  Its caller silently ignores the
  failure.

  Register the same TpmModel more than once has no effect other than
  wasting tpm_models[] slots: tpm_model_is_registered() is happy with
  the first one it finds.

Since we only ever register one model, and tpm_models[] has space for
just that one, this contraption even works.

Turn tpm_models[] into a straight map from enum TpmType to bool.  Much
simpler.

Cc: Stefan Berger <stefanb@us.ibm.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 include/sysemu/tpm_backend.h |  2 +-
 tpm.c                        | 37 +++++--------------------------------
 2 files changed, 6 insertions(+), 33 deletions(-)

Hi

On Thu, Aug 24, 2017 at 10:45 AM, Markus Armbruster <armbru@redhat.com> wrote:
> We have a strict separation between enum TpmModel and tpm_models[]:
>
> * TpmModel may have any number of members.  It just happens to have one.
>
> * tpm_register_model() uses the first empty slot in tmp_models[].
>
>   If you register more than tpm_models[] has space,
>   tpn_register_model() fails.  Its caller silently ignores the
>   failure.

tpm_

>
>   Register the same TpmModel more than once has no effect other than
>   wasting tpm_models[] slots: tpm_model_is_registered() is happy with
>   the first one it finds.
>
> Since we only ever register one model, and tpm_models[] has space for
> just that one, this contraption even works.
>
> Turn tpm_models[] into a straight map from enum TpmType to bool.  Much
> simpler.
>
> Cc: Stefan Berger <stefanb@us.ibm.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


> ---
>  include/sysemu/tpm_backend.h |  2 +-
>  tpm.c                        | 37 +++++--------------------------------
>  2 files changed, 6 insertions(+), 33 deletions(-)
>
> diff --git a/include/sysemu/tpm_backend.h b/include/sysemu/tpm_backend.h
> index 1d21c6b..b0a9731 100644
> --- a/include/sysemu/tpm_backend.h
> +++ b/include/sysemu/tpm_backend.h
> @@ -226,7 +226,7 @@ TPMVersion tpm_backend_get_tpm_version(TPMBackend *s);
>  TPMBackend *qemu_find_tpm(const char *id);
>
>  const TPMDriverOps *tpm_get_backend_driver(const char *type);
> -int tpm_register_model(enum TpmModel model);
> +void tpm_register_model(enum TpmModel model);
>  void tpm_register_driver(const TPMDriverOps *tdo);
>
>  #endif
> diff --git a/tpm.c b/tpm.c
> index 6f39ec9..7635fc7 100644
> --- a/tpm.c
> +++ b/tpm.c
> @@ -24,39 +24,12 @@
>  static QLIST_HEAD(, TPMBackend) tpm_backends =
>      QLIST_HEAD_INITIALIZER(tpm_backends);
>
> -
> -#define TPM_MAX_MODELS      1
> -
>  static TPMDriverOps const *be_drivers[TPM_TYPE__MAX];
> +static bool tpm_models[TPM_MODEL__MAX];
>
> -static enum TpmModel tpm_models[TPM_MAX_MODELS] = {
> -    TPM_MODEL__MAX,
> -};
> -
> -int tpm_register_model(enum TpmModel model)
> +void tpm_register_model(enum TpmModel model)
>  {
> -    int i;
> -
> -    for (i = 0; i < TPM_MAX_MODELS; i++) {
> -        if (tpm_models[i] == TPM_MODEL__MAX) {
> -            tpm_models[i] = model;
> -            return 0;
> -        }
> -    }
> -    error_report("Could not register TPM model");
> -    return 1;
> -}
> -
> -static bool tpm_model_is_registered(enum TpmModel model)
> -{
> -    int i;
> -
> -    for (i = 0; i < TPM_MAX_MODELS; i++) {
> -        if (tpm_models[i] == model) {
> -            return true;
> -        }
> -    }
> -    return false;
> +    tpm_models[model] = true;

Ah, no need for an assert() here indeed (it took me a minute).

>  }
>
>  const TPMDriverOps *tpm_get_backend_driver(const char *type)
> @@ -270,7 +243,7 @@ TPMInfoList *qmp_query_tpm(Error **errp)
>      TPMInfoList *info, *head = NULL, *cur_item = NULL;
>
>      QLIST_FOREACH(drv, &tpm_backends, list) {
> -        if (!tpm_model_is_registered(drv->fe_model)) {
> +        if (!tpm_models[drv->fe_model]) {
>              continue;
>          }
>          info = g_new0(TPMInfoList, 1);
> @@ -317,7 +290,7 @@ TpmModelList *qmp_query_tpm_models(Error **errp)
>      TpmModelList *head = NULL, *prev = NULL, *cur_item;
>
>      for (i = 0; i < TPM_MODEL__MAX; i++) {
> -        if (!tpm_model_is_registered(i)) {
> +        if (!tpm_models[i]) {
>              continue;
>          }
>          cur_item = g_new0(TpmModelList, 1);
> --
> 2.7.5
>
>

Marc-André Lureau <marcandre.lureau@gmail.com> writes:

> Hi
>
> On Thu, Aug 24, 2017 at 10:45 AM, Markus Armbruster <armbru@redhat.com> wrote:
>> We have a strict separation between enum TpmModel and tpm_models[]:
>>
>> * TpmModel may have any number of members.  It just happens to have one.
>>
>> * tpm_register_model() uses the first empty slot in tmp_models[].
>>
>>   If you register more than tpm_models[] has space,
>>   tpn_register_model() fails.  Its caller silently ignores the
>>   failure.
>
> tpm_

Will fix.

>>
>>   Register the same TpmModel more than once has no effect other than
>>   wasting tpm_models[] slots: tpm_model_is_registered() is happy with
>>   the first one it finds.
>>
>> Since we only ever register one model, and tpm_models[] has space for
>> just that one, this contraption even works.
>>
>> Turn tpm_models[] into a straight map from enum TpmType to bool.  Much
>> simpler.
>>
>> Cc: Stefan Berger <stefanb@us.ibm.com>
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>
> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Thanks!

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