[pulseaudio-discuss] [PATCH 11/11] pulsecore: srbchannel: Enable memfd support; pump protocol version

[Ahmed S. Darwish]

Hi Tanu,

On Thu, Oct 1, 2015 at 10:02 AM, Tanu Kaskinen <tanuk at iki.fi> wrote:
> On Sun, 2015-09-20 at 23:39 +0200, Ahmed S. Darwish wrote:
>> diff --git a/src/pulse/context.c b/src/pulse/context.c
>> index ede01fa..f272cd6 100644
>> --- a/src/pulse/context.c
>> +++ b/src/pulse/context.c
>> @@ -591,6 +591,8 @@ static void setup_context(pa_context *c, pa_iochannel *io) {
>>      pa_tagstruct_putu32(t, PA_PROTOCOL_VERSION | (c->do_shm ? 0x80000000U : 0));
>>      pa_tagstruct_put_arbitrary(t, cookie, sizeof(cookie));
>>
>> +    pa_tagstruct_put_boolean(t, pa_memfd_is_supported());
>
> This breaks compatibility with old servers that expect the tagstruct to
> end after the cookie.
>

Hmm, I thought that backward compatibility is only maintained from
the server toward its clients, and not also the other way around ;-)

> The "memfd supported" bit could be added to the version field like the
> "shm supported" bit. Another approach would be to do add a new command
> to do memfd negotiation before enabling srbchannel. Abusing the version
> field is ugly, adding another negotiation adds more connection setup
> overhead. I don't know which approach we should choose.
>

The daemon should support all older clients as a form of ABI. This
is maintained in the patch (even for srbchannels), and would be
even more important with the arise of xdg-app containers and the like.

But why should a new client library version support an older daemon?

Thanks a lot,

-- 
Darwish
http://darwish.chasingpointers.com