Re: [Qemu-devel] [PATCH 00/12][RFC] char: add flow control and fix guest_[open|close]

[Anthony Liguori <anthony@codemonkey.ws>]

On 08/01/2011 04:54 PM, Blue Swirl wrote:
> On Mon, Aug 1, 2011 at 2:22 PM, Anthony Liguori<aliguori@us.ibm.com>  wrote:
>> The char layer has been growing some nasty warts for some time now as we ask it
>> to do things it was never intended on doing.  It's been long over due for an
>> overhaul and its become evident to me that we need to address this first before
>> adding any more features to the char layer.
>>
>> This series is the start at sanitizing the char layer.  It effectively turns
>> the char layer into an internal pipe.  It supports flow control using an
>> intermediate ring queue for each direction.
>>
>> This series is an RFC because I don't think we should merge the series until we
>> completely convert the old style flow control users to the new style.
>
> The terms 'back-end' and 'front-end' could be improved. How about just
> 'device' or 'hw' and 'chrdev'?

It's all temporary as there currently is very little asymmetry. 
Historically, the biggest source of asymmetry was the fact that the 
back-end -> front-end path had flow control and the opposite direction 
didn't.

This series fixes that.  The only remaining asymmetry is the ioctl() 
call.  I think if we change the semantics of qemu_chr_event() though to 
have a return value and a data parameter, I think we can fold ioctl into 
event and ultimately fix that asymmetry.

Once that's done, there's no longer a distinction between front-end and 
back-end.  That makes CharDriverState act as basically a socketpair().

>
> The architecture could be described in for example qemu-tech.texi.

I'll include something for docs/ for the next submission.

Regards,

Anthony Liguori