Re: [Qemu-devel] [PATCH for-2.12] hw/riscv: Fix crashes with "-nodefaults"

[Paolo Bonzini]

On 23/03/2018 15:28, Peter Maydell wrote:
>> Note it's a null "backend", not necessarily a null "character device".
>> Your proposal, namely ensuring that be->chr == NULL is handled properly
>> in qemu_chr_fe_init, would be just fine.
> 
> Hmm, the chardev layer code seems to have more ends than I expect.
> The "frontend" is the UART model, right, and I thought the
> "backend" was the TCP/UDP/serial port/stdio/etc end of things,
> but those seem to be Chardevs? If those aren't the backend,
> then what is?

The naming of Chardev/CharBackend was modeled after
BlockDriverState/BlockBackend, and it's not great but at least it's
consistent. :/

The CharBackend struct essentially connects a Chardev and its user.  It
ought to be possible for the Chardev to be NULL.

Paolo

> What I'd like, anyway, is that every UART model can cope with being
> setup with a NULL 'chardev' property, and ideally that that doesn't
> require a lot of extra code per-UART, and doesn't require each UART
> to create a TYPE_CHARDEV_NULL.
>