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Fri, 20 Dec 2019 12:58:40 +0000 (UTC) Date: Fri, 20 Dec 2019 13:58:39 +0100 From: Kevin Wolf To: Markus Armbruster Subject: Re: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE Message-ID: <20191220125839.GG4019@dhcp-200-226.str.redhat.com> References: <20191219143818.1646168-1-mreitz@redhat.com> <20191219143818.1646168-3-mreitz@redhat.com> <20191220102656.GD4019@dhcp-200-226.str.redhat.com> <1812e968-1197-523e-7039-caf29e3bbc4b@redhat.com> <20191220112402.GE4019@dhcp-200-226.str.redhat.com> <87pngjgo2h.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87pngjgo2h.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: DCmT0yVxMFCg3NViDowRww-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 20.12.2019 um 13:48 hat Markus Armbruster geschrieben: > Kevin Wolf writes: >=20 > > Am 20.12.2019 um 11:48 hat Max Reitz geschrieben: > >> So if we kept writable and growable in the common base, then the schem= a > >> would give no information about what exports actually support them. > >>=20 > >> On one hand, I don=E2=80=99t know whether it=E2=80=99s important to ha= ve this > >> information in a static form, or whether it=E2=80=99s sufficient to le= arn at > >> runtime. > >>=20 > >> On the other, I don=E2=80=99t know whether it=E2=80=99s important to h= ave those fields > >> in the base or not. Would it make a difference on the wire? > > > > Not for the command itself, so I think we're free to change it later. I= t > > might make a difference for introspection, though, not sure. Markus? >=20 > QAPI schema introspection is designed to hide the difference between > local members and base members. You can move members to or from a base > type freely without affecting introspection. Even if that creates or > deletes the base type. Good, that's helpful. So I can split the nbd-server-add argument type into a base that is reused as a union branch and the rest without potentially breaking anything. I suppose moving a field between a union base and all variants does still result in different introspection even though the accepted inputs are the same. Is this kind of movement still allowed unconditionally or should we be more careful with something like this? Kevin