[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] ns16550.c's poll_port variable

  • To: Jan Beulich <JBeulich@xxxxxxxx>
  • From: Keir Fraser <keir.xen@xxxxxxxxx>
  • Date: Fri, 04 May 2012 14:27:03 +0100
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxx>
  • Delivery-date: Fri, 04 May 2012 13:27:31 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac0p+ZePRBwmIx2VskqK62N/W2PmeA==
  • Thread-topic: ns16550.c's poll_port variable

On 04/05/2012 13:46, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:

>>>> On 04.05.12 at 14:03, Keir Fraser <keir@xxxxxxx> wrote:
>> On 04/05/2012 12:05, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
>>>> I'm unclear on exactly what you want to optimise away? Certainly the 8
>>>> bytes
>>>> per CPU of the poll_port variable isn't worth much optimising effort.
>>> Certainly not (and as you say they are actually needed, even if
>>> only rarely). But the pointlessly running timer(s) might be, as might
>>> the buffer(s) set up via serial_async_transmit().
>> We could delay {init,setup}_postirq until a corresponding serial handle has
>> been created via serial_parse_handle()? The logic might be a bit ugly and
>> spread across both serial.c and ns16550.c but not actually particularly
>> complicated?
> I think this can be done entirely in serial.c - serial_init_postirq()
> would directly call any drivers that already got a handle parsed
> for them, and serial_parse_handle() would need to call
> ->init_postirq() for any driver that didn't have it called already.
> serial_suspend() and serial_resume() should then call drivers only
> if they previously had ->init_postirq() called.

Ah yes, that would work. Feel free to make a patch.

 -- Keir

> I definitely want to avoid putting any part of this into ns16550.c,
> as it would need to be replicated for ARM's pl011.c as well as any
> future ones (I'm now mostly done with an EHCI debug port driver,
> but due to feature freeze won't be able to post this as other than
> an RFC any time soon; xHCI appears to also have a debug port,
> so in the future that might become a third alternative).
> Jan

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.