Re: [Qemu-devel] [PATCH v3 2/4] char: Add ability to provide a callback when write won't return -EAGAIN

[Paul Brook]

> I sent out this series as a "feeler" to see if the approach was
> acceptable.
> 
> Paul didn't reply to my reply addressing his concern, so I take that as
> he's OK with the approach as well :-)

I'd probably exposed this as an asyncronous write rather than nonblocking 
operation. However both have their issues and I guess for character devices 
your approach makes sense (c.f. block devices where we want concurrent 
transfers).

It would be useful to have a debugging mode where the chardev layer 
deliberately returns spurious EAGAIN and short writes. Otherwise you've got a 
lot of very poorly tested device fallback code. I have low confidence in 
getting this right first time :-)

Paul