linux/drivers/char/hvc_irq.c
Christian Borntraeger 611e097d77 hvc_console: rework setup to replace irq functions with callbacks
This patch tries to change hvc_console to not use request_irq/free_irq if
the backend does not use irqs. This allows virtio_console to use hvc_console
without having a linker reference to request_irq/free_irq.

In addition, together with patch 2/3 it improves the performance for virtio
console input. (an earlier version of this patch was tested by Yajin on lguest)

The irq specific code is moved to hvc_irq.c and selected by the drivers that
use irqs (System p, System i, XEN).

I replaced "int irq" with the opaque "int data". The request_irq and
free_irq calls are replaced with notifier_add and notifier_del. I have also
changed the code a bit to call the notifier_add and notifier_del inside the
spinlock area as the callbacks are found via hp->ops.

Changes since last version:
o remove ifdef
o reintroduce "irq_requested" as "notified"
o cleanups, sparse..

I did not move the timer based polling into a separate polling scheme. I
played with several variants, but it seems we need to sleep/schedule in
a thread even for irq based consoles, as there are throttleing and buffer
size constraints.

I also kept hvc_struct defined in hvc_console.h so that hvc_irq.c can access
the irq_requested element.

Feedback is appreciated. virtio_console is currently the only available console
for kvm on s390. I plan to push this change as soon as all affected parties
agree on it. I would love to get test results from System p, Xen etc.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2008-07-25 12:06:06 +10:00

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801 B
C

/*
* Copyright IBM Corp. 2001,2008
*
* This file contains the IRQ specific code for hvc_console
*
*/
#include <linux/interrupt.h>
#include "hvc_console.h"
static irqreturn_t hvc_handle_interrupt(int irq, void *dev_instance)
{
/* if hvc_poll request a repoll, then kick the hvcd thread */
if (hvc_poll(dev_instance))
hvc_kick();
return IRQ_HANDLED;
}
/*
* For IRQ based systems these callbacks can be used
*/
int notifier_add_irq(struct hvc_struct *hp, int irq)
{
int rc;
if (!irq) {
hp->irq_requested = 0;
return 0;
}
rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED,
"hvc_console", hp);
if (!rc)
hp->irq_requested = 1;
return rc;
}
void notifier_del_irq(struct hvc_struct *hp, int irq)
{
if (!irq)
return;
free_irq(irq, hp);
hp->irq_requested = 0;
}