staging: unisys: visorchannel: Add peek function

According to unisys, the s_par hypervisor has a bug in which it never
triggers an interrupt.  That makes the visornic effectively a 2ms poll
loop.  In order to just have the rx thread shceduling a napi poll every
2ms, lets instead give it the chance to check the response queue for
data before we schedule.  This helper provides that functionality

Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/unisys/include/visorbus.h b/drivers/staging/unisys/include/visorbus.h
index a0144c6..9235536 100644 (file)
--- a/drivers/staging/unisys/include/visorbus.h
+++ b/drivers/staging/unisys/include/visorbus.h
@@ -201,6 +201,8 @@ bool visorchannel_signalremove(struct visorchannel *channel, u32 queue,
                               void *msg);
 bool visorchannel_signalinsert(struct visorchannel *channel, u32 queue,
                               void *msg);
+bool visorchannel_signalempty(struct visorchannel *channel, u32 queue);
+
 int visorchannel_signalqueue_slots_avail(struct visorchannel *channel,
                                         u32 queue);
 int visorchannel_signalqueue_max_slots(struct visorchannel *channel, u32 queue);

diff --git a/drivers/staging/unisys/visorbus/visorchannel.c b/drivers/staging/unisys/visorbus/visorchannel.c
index 2422464..6da7e49 100644 (file)
--- a/drivers/staging/unisys/visorbus/visorchannel.c
+++ b/drivers/staging/unisys/visorbus/visorchannel.c
@@ -430,6 +430,27 @@ visorchannel_signalremove(struct visorchannel *channel, u32 queue, void *msg)
 }
 EXPORT_SYMBOL_GPL(visorchannel_signalremove);
 
+bool
+visorchannel_signalempty(struct visorchannel *channel, u32 queue)
+{
+       unsigned long flags = 0;
+       struct signal_queue_header sig_hdr;
+       bool rc = false;
+
+       if (channel->needs_lock)
+               spin_lock_irqsave(&channel->remove_lock, flags);
+
+       if (!sig_read_header(channel, queue, &sig_hdr))
+               rc = true;
+       if (sig_hdr.head == sig_hdr.tail)
+               rc = true;
+       if (channel->needs_lock)
+               spin_unlock_irqrestore(&channel->remove_lock, flags);
+
+       return rc;
+}
+EXPORT_SYMBOL_GPL(visorchannel_signalempty);
+
 static bool
 signalinsert_inner(struct visorchannel *channel, u32 queue, void *msg)
 {