Re: [RFC PATCH v2 3/5] exec/memattrs: Introduce MemTxAttrs::bus_perm field

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 8/23/21 21:04, David Hildenbrand wrote:
> On 23.08.21 20:41, Peter Xu wrote:
>> On Mon, Aug 23, 2021 at 06:41:55PM +0200, Philippe Mathieu-Daudé wrote:
>>> +/* Permission to restrict bus memory accesses. See
>>> MemTxAttrs::bus_perm */
>>> +enum {
>>> +    MEMTXPERM_UNSPECIFIED   = 0,
>>> +    MEMTXPERM_UNRESTRICTED  = 1,
>>> +    MEMTXPERM_RAM_DEVICE    = 2,
>>> +};
>>
>> Is there a difference between UNSPECIFIED and UNRESTRICTED?
>>
>> If no, should we merge them?
>>
> 
> I'd assume MEMTXPERM_UNSPECIFIED has to be treated like
> MEMTXPERM_UNRESTRICTED, so I'd also think we should just squash them.

For now they are treated the same way, but ideally we should
explicitly classify bus accesses and remove the MEMTXPERM_UNSPECIFIED.

While we can use the same definition with comments, I think having
different definitions ease maintainance (thinking of git-grep), but
if we know we will never classify/convert the devices, then indeed
having MEMTXPERM_UNSPECIFIED is pointless and confusing.