[patch 21/29] x86/hpet: Add function to select a /dev/hpet channel

[Thomas Gleixner]

If CONFIG_HPET=y is enabled the x86 specific HPET code should reserve at
least one channel for the /dev/hpet character device, so that not all
channels are absorbed for per CPU clockevent devices.

Create a function to assign HPET_MODE_DEVICE so the rework of the
clockevents allocation code can utilize the mode information instead of
reducing the number of evaluated channels by #ifdef hackery.

The function is not yet used, but provided as a separate patch for ease of
review. It will be used when the rework of the clockevent selection takes
place.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/kernel/hpet.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -228,8 +228,25 @@ static void __init hpet_reserve_platform
 	hpet_alloc(&hd);
 
 }
+
+static void __init hpet_select_device_channel(void)
+{
+	int i;
+
+	for (i = 0; i < hpet_base.nr_channels; i++) {
+		struct hpet_channel *hc = hpet_base.channels + i;
+
+		/* Associate the first unused channel to /dev/hpet */
+		if (hc->mode == HPET_MODE_UNUSED) {
+			hc->mode = HPET_MODE_DEVICE;
+			return;
+		}
+	}
+}
+
 #else
 static inline void hpet_reserve_platform_timers(void) { }
+static inline void hpet_select_device_channel(void) {}
 #endif
 
 /* Common HPET functions */