Gerd Hoffmann <kra...@redhat.com> writes:
> Hi,
>
>> Now let's take another step back: a character device is just a file.
>> Why can't we use plain ChardevFile for it?
>
> It's not.
A Unix character device is a special file.
> First, the file backend allows input and output being different files,
> and the input file is optional. That doesn't make sense for the
> parallel/serial port case.
>
> Second, it's actually more than a file. The guest can change device
> parameters such as the baudrate on the virtual device and qemu will
> apply those changes to the host device.
>
> IMO it is different enough to have its own type.
Special files support some special operations. I didn't propose to drop
support for the special operations and treat special files exactly like
regular files. I asked whether we really need a completely separate way
to configure them.
The argument for separate configuration is file's capability to split
input and output. Okay.
But why nested discriminators?
regular files: type=file
serial : type=port, data.type=serial
parallel : type=port, data.type=parallel
Simpler, and closer to existing -chardev:
regular files: type=file
serial : type=serial
parallel : type=parallel
I also dislike the pointless '"data" : {}' required by type pty and
null, but I can't figure out how to express 'void' in the schema.
[...]
