Re: [Qemu-devel] [PATCH v3 4/4] serial: only resample THR interrupt on rising edge of IER.THRI

[Paolo Bonzini <pbonzini@redhat.com>]

On 15/12/2014 17:05, Dr. David Alan Gilbert wrote:
> > +            if ((changed & UART_IER_MSI) && s->poll_msl >= 0) {
> >                  if (s->ier & UART_IER_MSI) {
> >                       s->poll_msl = 1;
> >                       serial_update_msl(s);
> 
> This MSI stuff, this change is just intended to do the same as you're
> doing for THRI and making it change based?   The commit message and title
> doens't mention it.

It has no change.  If MSI = 1, there is already a timer ticking every
100th of a second to poll the modem status, so it's useless to go
through serial_udpate_msl/timer_del/...

It's just because I have the changed bits at hand now.

BTW, looks like the poll_msl subsection after all was not necessary.  It
can be gleaned by ANDing "does CHR_IOCTL_SERIAL_GET_TIOCM work?" (which
is immutable state depending on the command-line configuration" with
IER.MSI.

Paolo