Re: [PATCH RFC XEN v1 01/14] xen: arm: Add gic_hw_desc

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 15/12/15 16:21, Ian Campbell wrote:
> On Tue, 2015-12-15 at 16:15 +0000, Stefano Stabellini wrote:
>> On Wed, 9 Dec 2015, Ian Campbell wrote:
>>> Because the enum gic_version values do not correspond to the gic
>>> version (in order to allow space for variants such as GICv2m, although
>>> that is currently not present) logging the raw value is not terribly
>>> useful. Provide gic_hw_desc which provides a string describing each
>>> GIC version.
>>>
>>> Will be used in a later patch.
>>>
>>> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
>>> ---
>>>  xen/arch/arm/gic.c        | 14 ++++++++++++++
>>>  xen/include/asm-arm/gic.h |  1 +
>>>  2 files changed, 15 insertions(+)
>>>
>>> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
>>> index 1e1e5ba..bea39d6 100644
>>> --- a/xen/arch/arm/gic.c
>>> +++ b/xen/arch/arm/gic.c
>>> @@ -62,6 +62,20 @@ enum gic_version gic_hw_version(void)
>>>     return gic_hw_ops->info->hw_version;
>>>  }
>>>  
>>> +const char *gic_hw_desc(enum gic_version v)
>>> +{
>>> +    switch (v) {
>>> +    case GIC_V2: return "GIC v2";
>>> +    case GIC_V3: return "GIC v3";
>>> +    }
>>> +
>>> +    /*
>>> +     * The compiler ought to gripe if the above doesn't cover all enum
>>> +     * gic_version, in case some version doesn't.
>>> +     */
>>> +    return "Unknown";
>> default: ?
> Deliberately not, since that would quash the expected compiler warning.

What expected compiler warning?

That switch statement, complete or not, is always valid.

The only way you can plausibly get a warning is to drop the return
"Unknown";, and have the compiler warning about a missing return
statement.  This, however, will backfire on older compilers which
can't/don't check whether the switch statement is complete.

~Andrew