[RFC 1/3] hvc_console: rework setup to replace irq functions with callbacks

From: Christian Borntraeger
Date: Tue Jun 03 2008 - 08:47:14 EST

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.

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 "irq" with the opaque name "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.

Feedback is appreciated.

Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>

---
drivers/char/Kconfig | 8 ++++
drivers/char/Makefile | 1
drivers/char/hvc_console.c | 80
++++++++++-----------------------------------
drivers/char/hvc_console.h | 34 ++++++++++++++++---
drivers/char/hvc_irq.c | 37 ++++++++++++++++++++
drivers/char/hvc_iseries.c | 2 +
drivers/char/hvc_vio.c | 2 +
drivers/char/hvc_xen.c | 2 +
8 files changed, 100 insertions(+), 66 deletions(-)

Index: kvm/drivers/char/Kconfig
===================================================================
--- kvm.orig/drivers/char/Kconfig
+++ kvm/drivers/char/Kconfig
@@ -588,11 +588,17 @@ config HVC_DRIVER
It will automatically be selected if one of the back-end console drivers
is selected.

+config HVC_IRQ
+ bool
+ help
+ Infrastructure for using the IRQ code for HVC console.
+ It will automatically be selected by the drivers that need it.

config HVC_CONSOLE
bool "pSeries Hypervisor Virtual Console support"
depends on PPC_PSERIES
select HVC_DRIVER
+ select HVC_IRQ
help
pSeries machines when partitioned support a hypervisor virtual
console. This driver allows each pSeries partition to have a console
@@ -603,6 +609,7 @@ config HVC_ISERIES
depends on PPC_ISERIES
default y
select HVC_DRIVER
+ select HVC_IRQ
help
iSeries machines support a hypervisor virtual console.

@@ -624,6 +631,7 @@ config HVC_XEN
bool "Xen Hypervisor Console support"
depends on XEN
select HVC_DRIVER
+ select HVC_IRQ
default y
help
Xen virtual console device driver
Index: kvm/drivers/char/Makefile
===================================================================
--- kvm.orig/drivers/char/Makefile
+++ kvm/drivers/char/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_HVC_ISERIES) += hvc_iseries
obj-$(CONFIG_HVC_RTAS) += hvc_rtas.o
obj-$(CONFIG_HVC_BEAT) += hvc_beat.o
obj-$(CONFIG_HVC_DRIVER) += hvc_console.o
+obj-$(CONFIG_HVC_IRQ) += hvc_irq.o
obj-$(CONFIG_HVC_XEN) += hvc_xen.o
obj-$(CONFIG_VIRTIO_CONSOLE) += virtio_console.o
obj-$(CONFIG_RAW_DRIVER) += raw.o
Index: kvm/drivers/char/hvc_console.c
===================================================================
--- kvm.orig/drivers/char/hvc_console.c
+++ kvm/drivers/char/hvc_console.c
@@ -75,23 +75,6 @@ static int hvc_init(void);
static int sysrq_pressed;
#endif

-struct hvc_struct {
- spinlock_t lock;
- int index;
- struct tty_struct *tty;
- unsigned int count;
- int do_wakeup;
- char *outbuf;
- int outbuf_size;
- int n_outbuf;
- uint32_t vtermno;
- struct hv_ops *ops;
- int irq_requested;
- int irq;
- struct list_head next;
- struct kref kref; /* ref count & hvc_struct lifetime */
-};
-
/* dynamic list of hvc_struct instances */
static LIST_HEAD(hvc_structs);

@@ -300,26 +283,12 @@ int hvc_instantiate(uint32_t vtermno, in
}

/* Wake the sleeping khvcd */
-static void hvc_kick(void)
+void hvc_kick(void)
{
hvc_kicked = 1;
wake_up_process(hvc_task);
}

-static int hvc_poll(struct hvc_struct *hp);
-
-/*
- * NOTE: This API isn't used if the console adapter doesn't support
interrupts.
- * In this case the console is poll driven.
- */
-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;
-}
-
static void hvc_unthrottle(struct tty_struct *tty)
{
hvc_kick();
@@ -333,7 +302,6 @@ static int hvc_open(struct tty_struct *t
{
struct hvc_struct *hp;
unsigned long flags;
- int irq = 0;
int rc = 0;

/* Auto increments kref reference if found. */
@@ -352,18 +320,15 @@ static int hvc_open(struct tty_struct *t
tty->low_latency = 1; /* Makes flushes to ldisc synchronous. */

hp->tty = tty;
- /* Save for request_irq outside of spin_lock. */
- irq = hp->irq;
- if (irq)
- hp->irq_requested = 1;
+
+ if (hp->ops->notifier_add)
+ rc = hp->ops->notifier_add(hp, hp->data);

spin_unlock_irqrestore(&hp->lock, flags);
- /* check error, fallback to non-irq */
- if (irq)
- rc = request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED, "hvc_console",
hp);
+

/*
- * If the request_irq() fails and we return an error. The tty layer
+ * If the notifier fails we return an error. The tty layer
* will call hvc_close() after a failed open but we don't want to clean
* up there so we'll clean up here and clear out the previously set
* tty fields and return the kref reference.
@@ -371,7 +336,6 @@ static int hvc_open(struct tty_struct *t
if (rc) {
spin_lock_irqsave(&hp->lock, flags);
hp->tty = NULL;
- hp->irq_requested = 0;
spin_unlock_irqrestore(&hp->lock, flags);
tty->driver_data = NULL;
kref_put(&hp->kref, destroy_hvc_struct);
@@ -386,7 +350,6 @@ static int hvc_open(struct tty_struct *t
static void hvc_close(struct tty_struct *tty, struct file * filp)
{
struct hvc_struct *hp;
- int irq = 0;
unsigned long flags;

if (tty_hung_up_p(filp))
@@ -404,9 +367,8 @@ static void hvc_close(struct tty_struct
spin_lock_irqsave(&hp->lock, flags);

if (--hp->count == 0) {
- if (hp->irq_requested)
- irq = hp->irq;
- hp->irq_requested = 0;
+ if (hp->ops->notifier_del)
+ hp->ops->notifier_del(hp, hp->data);

/* We are done with the tty pointer now. */
hp->tty = NULL;
@@ -418,10 +380,6 @@ static void hvc_close(struct tty_struct
* waking periodically to check chars_in_buffer().
*/
tty_wait_until_sent(tty, HVC_CLOSE_WAIT);
-
- if (irq)
- free_irq(irq, hp);
-
} else {
if (hp->count < 0)
printk(KERN_ERR "hvc_close %X: oops, count is %d\n",
@@ -436,7 +394,6 @@ static void hvc_hangup(struct tty_struct
{
struct hvc_struct *hp = tty->driver_data;
unsigned long flags;
- int irq = 0;
int temp_open_count;

if (!hp)
@@ -458,13 +415,12 @@ static void hvc_hangup(struct tty_struct
hp->count = 0;
hp->n_outbuf = 0;
hp->tty = NULL;
- if (hp->irq_requested)
- /* Saved for use outside of spin_lock. */
- irq = hp->irq;
- hp->irq_requested = 0;
+
+ if (hp->ops->notifier_del)
+ hp->ops->notifier_del(hp, hp->data);
+
spin_unlock_irqrestore(&hp->lock, flags);
- if (irq)
- free_irq(irq, hp);
+
while(temp_open_count) {
--temp_open_count;
kref_put(&hp->kref, destroy_hvc_struct);
@@ -575,7 +531,7 @@ static u32 timeout = MIN_TIMEOUT;
#define HVC_POLL_READ 0x00000001
#define HVC_POLL_WRITE 0x00000002

-static int hvc_poll(struct hvc_struct *hp)
+int hvc_poll(struct hvc_struct *hp)
{
struct tty_struct *tty;
int i, n, poll_mask = 0;
@@ -602,10 +558,10 @@ static int hvc_poll(struct hvc_struct *h
if (test_bit(TTY_THROTTLED, &tty->flags))
goto throttled;

- /* If we aren't interrupt driven and aren't throttled, we always
+ /* If we aren't notifier driven and aren't throttled, we always
* request a reschedule
*/
- if (hp->irq == 0)
+ if (!hp->ops->notifier_add)
poll_mask |= HVC_POLL_READ;

/* Read data if any */
@@ -739,7 +695,7 @@ static const struct tty_operations hvc_o
.chars_in_buffer = hvc_chars_in_buffer,
};

-struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int irq,
+struct hvc_struct __devinit *hvc_alloc(uint32_t vtermno, int data,
struct hv_ops *ops, int outbuf_size)
{
struct hvc_struct *hp;
@@ -760,7 +716,7 @@ struct hvc_struct __devinit *hvc_alloc(u
memset(hp, 0x00, sizeof(*hp));

hp->vtermno = vtermno;
- hp->irq = irq;
+ hp->data = data;
hp->ops = ops;
hp->outbuf_size = outbuf_size;
hp->outbuf = &((char *)hp)[ALIGN(sizeof(*hp), sizeof(long))];
Index: kvm/drivers/char/hvc_console.h
===================================================================
--- kvm.orig/drivers/char/hvc_console.h
+++ kvm/drivers/char/hvc_console.h
@@ -42,22 +42,48 @@
*/
#define HVC_ALLOC_TTY_ADAPTERS 8

+struct hvc_struct {
+ spinlock_t lock;
+ int index;
+ struct tty_struct *tty;
+ unsigned int count;
+ int do_wakeup;
+ char *outbuf;
+ int outbuf_size;
+ int n_outbuf;
+ uint32_t vtermno;
+ struct hv_ops *ops;
+ int data;
+ struct list_head next;
+ struct kref kref; /* ref count & hvc_struct lifetime */
+};

/* implemented by a low level driver */
struct hv_ops {
int (*get_chars)(uint32_t vtermno, char *buf, int count);
int (*put_chars)(uint32_t vtermno, const char *buf, int count);
-};

-struct hvc_struct;
+ /* Callbacks for notification. Called in open and close */
+ int (*notifier_add)(struct hvc_struct *hp, int data);
+ void (*notifier_del)(struct hvc_struct *hp, int data);
+};

/* Register a vterm and a slot index for use as a console (console_init) */
extern int hvc_instantiate(uint32_t vtermno, int index, struct hv_ops *ops);

/* register a vterm for hvc tty operation (module_init or hotplug add) */
-extern struct hvc_struct * __devinit hvc_alloc(uint32_t vtermno, int irq,
+extern struct hvc_struct * __devinit hvc_alloc(uint32_t vtermno, int data,
struct hv_ops *ops, int outbuf_size);
-/* remove a vterm from hvc tty operation (modele_exit or hotplug remove) */
+/* remove a vterm from hvc tty operation (module_exit or hotplug remove) */
extern int __devexit hvc_remove(struct hvc_struct *hp);

+/* data available */
+int hvc_poll(struct hvc_struct *hp);
+void hvc_kick(void);
+
+#ifdef CONFIG_HVC_IRQ
+/* default notifier for irq based notification */
+extern int notifier_add_irq(struct hvc_struct *hp, int irq);
+extern void notifier_del_irq(struct hvc_struct *hp, int irq);
+#endif
#endif // HVC_CONSOLE_H
Index: kvm/drivers/char/hvc_irq.c
===================================================================
--- /dev/null
+++ kvm/drivers/char/hvc_irq.c
@@ -0,0 +1,37 @@
+/*
+ * 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)
+{
+ if (!irq)
+ return 0;
+ return request_irq(irq, hvc_handle_interrupt, IRQF_DISABLED,
+ "hvc_console", hp);
+}
+
+void notifier_del_irq(struct hvc_struct *hp, int irq)
+{
+ if (!irq)
+ return;
+ free_irq(irq, hp);
+}
+
Index: kvm/drivers/char/hvc_iseries.c
===================================================================
--- kvm.orig/drivers/char/hvc_iseries.c
+++ kvm/drivers/char/hvc_iseries.c
@@ -200,6 +200,8 @@ done:
static struct hv_ops hvc_get_put_ops = {
.get_chars = get_chars,
.put_chars = put_chars,
+ .notifier_add = notifier_add_irq,
+ .notifier_del = notifier_del_irq,
};

static int __devinit hvc_vio_probe(struct vio_dev *vdev,
Index: kvm/drivers/char/hvc_vio.c
===================================================================
--- kvm.orig/drivers/char/hvc_vio.c
+++ kvm/drivers/char/hvc_vio.c
@@ -80,6 +80,8 @@ static int filtered_get_chars(uint32_t v
static struct hv_ops hvc_get_put_ops = {
.get_chars = filtered_get_chars,
.put_chars = hvc_put_chars,
+ .notifier_add = notifier_add_irq,
+ .notifier_del = notifier_del_irq,
};

static int __devinit hvc_vio_probe(struct vio_dev *vdev,
Index: kvm/drivers/char/hvc_xen.c
===================================================================
--- kvm.orig/drivers/char/hvc_xen.c
+++ kvm/drivers/char/hvc_xen.c
@@ -95,6 +95,8 @@ static int read_console(uint32_t vtermno
static struct hv_ops hvc_ops = {
.get_chars = read_console,
.put_chars = write_console,
+ .notifier_add = notifier_add_irq,
+ .notifier_del = notifier_del_irq,
};

static int __init xen_init(void)
--
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