From ffb8f86a9ca8a5946b8f18e90cc9758ebad74c73 Mon Sep 17 00:00:00 2001
From: Achilleas Anagnostopoulos <achilleas.imap.mbox@gmail.com>
Date: Sat, 8 Jul 2017 12:25:21 +0100
Subject: [PATCH] Each driver should manually register a probe function for use
 by hal

This commit removes the HWProbes() function from the console and tty
packages and replaces it with a global ProbeFuncs slice which is fetched
by the hal package when the hardware autodetection code runs.

Each driver should provide an init() function that appends a probe function
to the global ProbeFuncs slice.

This approach allows us to support conditional compilation of drivers in
the future (e.g. using build tags)
---
 src/gopheros/device/tty/probe.go              | 14 +++++++-------
 src/gopheros/device/tty/vt.go                 |  6 ++++--
 src/gopheros/device/video/console/probe.go    | 13 +++++--------
 src/gopheros/device/video/console/vga_text.go | 17 +++++++++--------
 src/gopheros/kernel/hal/hal.go                |  4 ++--
 5 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/src/gopheros/device/tty/probe.go b/src/gopheros/device/tty/probe.go
index 6911b0b..ebc070a 100644
--- a/src/gopheros/device/tty/probe.go
+++ b/src/gopheros/device/tty/probe.go
@@ -2,10 +2,10 @@ package tty
 
 import "gopheros/device"
 
-// HWProbes returns a slice of device.ProbeFn that can be used by the hal
-// package to probe for TTY device hardware.
-func HWProbes() []device.ProbeFn {
-	return []device.ProbeFn{
-		probeForVT,
-	}
-}
+var (
+	// ProbeFuncs is a slice of device probe functions
+	// that is used by the hal package to probe for TTY
+	// hardware. Each driver should use an init() block
+	// to append its probe function to this list.
+	ProbeFuncs []device.ProbeFn
+)
diff --git a/src/gopheros/device/tty/vt.go b/src/gopheros/device/tty/vt.go
index a2f896c..4dda34c 100644
--- a/src/gopheros/device/tty/vt.go
+++ b/src/gopheros/device/tty/vt.go
@@ -260,6 +260,8 @@ func (t *VT) DriverVersion() (uint16, uint16, uint16) {
 // DriverInit initializes this driver.
 func (t *VT) DriverInit() *kernel.Error { return nil }
 
-func probeForVT() device.Driver {
-	return NewVT(DefaultTabWidth, DefaultScrollback)
+func init() {
+	ProbeFuncs = append(ProbeFuncs, func() device.Driver {
+		return NewVT(DefaultTabWidth, DefaultScrollback)
+	})
 }
diff --git a/src/gopheros/device/video/console/probe.go b/src/gopheros/device/video/console/probe.go
index a2a47d3..1981378 100644
--- a/src/gopheros/device/video/console/probe.go
+++ b/src/gopheros/device/video/console/probe.go
@@ -5,12 +5,9 @@ import "gopheros/kernel/hal/multiboot"
 
 var (
 	getFramebufferInfoFn = multiboot.GetFramebufferInfo
-)
 
-// HWProbes returns a slice of device.ProbeFn that can be used by the hal
-// package to probe for console device hardware.
-func HWProbes() []device.ProbeFn {
-	return []device.ProbeFn{
-		probeForVgaTextConsole,
-	}
-}
+	// ProbeFuncs is a slice of device probe functions that is used by
+	// the hal package to probe for console device hardware. Each driver
+	// should use an init() block to append its probe function to this list.
+	ProbeFuncs []device.ProbeFn
+)
diff --git a/src/gopheros/device/video/console/vga_text.go b/src/gopheros/device/video/console/vga_text.go
index 55e5589..fffa4ec 100644
--- a/src/gopheros/device/video/console/vga_text.go
+++ b/src/gopheros/device/video/console/vga_text.go
@@ -199,14 +199,15 @@ func (cons *VgaTextConsole) DriverVersion() (uint16, uint16, uint16) {
 // DriverInit initializes this driver.
 func (cons *VgaTextConsole) DriverInit() *kernel.Error { return nil }
 
-// probeForVgaTextConsole checks for the presence of a vga text console.
-func probeForVgaTextConsole() device.Driver {
-	var drv device.Driver
+func init() {
+	ProbeFuncs = append(ProbeFuncs, func() device.Driver {
+		var drv device.Driver
 
-	fbInfo := getFramebufferInfoFn()
-	if fbInfo.Type == multiboot.FramebufferTypeEGA {
-		drv = NewVgaTextConsole(fbInfo.Width, fbInfo.Height, uintptr(fbInfo.PhysAddr))
-	}
+		fbInfo := getFramebufferInfoFn()
+		if fbInfo.Type == multiboot.FramebufferTypeEGA {
+			drv = NewVgaTextConsole(fbInfo.Width, fbInfo.Height, uintptr(fbInfo.PhysAddr))
+		}
 
-	return drv
+		return drv
+	})
 }
diff --git a/src/gopheros/kernel/hal/hal.go b/src/gopheros/kernel/hal/hal.go
index 036be4e..3f5d06f 100644
--- a/src/gopheros/kernel/hal/hal.go
+++ b/src/gopheros/kernel/hal/hal.go
@@ -23,12 +23,12 @@ func ActiveTTY() tty.Device {
 // DetectHardware probes for hardware devices and initializes the appropriate
 // drivers.
 func DetectHardware() {
-	consoles := probe(console.HWProbes())
+	consoles := probe(console.ProbeFuncs)
 	if len(consoles) != 0 {
 		devices.activeConsole = consoles[0].(console.Device)
 	}
 
-	ttys := probe(tty.HWProbes())
+	ttys := probe(tty.ProbeFuncs)
 	if len(ttys) != 0 {
 		devices.activeTTY = ttys[0].(tty.Device)
 		devices.activeTTY.AttachTo(devices.activeConsole)