[Qemu-devel] Re: [PATCH v7 4/6] char: Add qemu_chr_write_nb() for nonblocking writes

[Paul Brook]

> I really dislike the idea of adding another function for this.  Can you
> explain why you need this functionality for virtio-console and why this
> functionality isn't needed for everything else?

This functionality should (in principle) be used by all serial port 
implementations.

Physical serial ports are sufficiently crufty and low-performance that noone 
actually uses them nowadays.  I expect that the only significant real-world 
use is for serial consoles, which never send enough data to care that writes 
stall the whole machine.

With virtio-serial we've made serial ports a viable solution to a whole range 
of problems.  It's likely that applications that may send nontrivial amounts 
of data, or clients will not be ready to process the data immediately.

Paul