Subject: Re: [PATCH] SMU LED driver

From: Michael Hanselmann <[email-masked]>
Date: Sun, 14 Jan 2007 14:31:19 +0100

On Mon, Jan 08, 2007 at 12:02:45PM +1100, Benjamin Herrenschmidt wrote:
> Just have 1 request allocated once for all. Then, have a global set to
> what status you want the LED at. Once the completion of any request
> arrives, if the new status is different from what you want, send a new
> one to fix it up :-)

Implemented that. See below.

There's a race condition between setting the LED value and unloading the
module. smu_led_exit can't return an error. Is it possible to prevent
unloading the module while an SMU request is still running, and if yes,
how?

Signed-off-by: Michael Hanselmann <[email-masked]>

---
diff -Nrup --exclude-from linux-exclude-from linux-2.6.19.1.orig/drivers/macintosh/Kconfig linux-2.6.19.1/drivers/macintosh/Kconfig
--- linux-2.6.19.1.orig/drivers/macintosh/Kconfig	2007-01-14 12:58:25.000000000 +0100
+++ linux-2.6.19.1/drivers/macintosh/Kconfig	2007-01-14 13:03:49.000000000 +0100
@@ -107,6 +107,15 @@ config PMAC_SMU
 	  on the "SMU" system control chip which replaces the old PMU.
 	  If you don't know, say Y.
 
+config PMAC_SMU_LED
+	tristate "Support for the PowerMac front LED"
+	depends on PMAC_SMU
+	select NEW_LEDS
+	select LEDS_CLASS
+	help
+	  Support the front LED on PowerMacs as a generic LED that can be
+	  triggered by any of the supported triggers.
+
 config PMAC_APM_EMU
 	tristate "APM emulation"
 	depends on PPC_PMAC && PPC32 && PM && ADB_PMU
diff -Nrup --exclude-from linux-exclude-from linux-2.6.19.1.orig/drivers/macintosh/Makefile linux-2.6.19.1/drivers/macintosh/Makefile
--- linux-2.6.19.1.orig/drivers/macintosh/Makefile	2007-01-14 12:58:25.000000000 +0100
+++ linux-2.6.19.1/drivers/macintosh/Makefile	2007-01-14 13:03:49.000000000 +0100
@@ -17,6 +17,7 @@ obj-$(CONFIG_PMAC_BACKLIGHT)	+= via-pmu-
 obj-$(CONFIG_ADB_CUDA)		+= via-cuda.o
 obj-$(CONFIG_PMAC_APM_EMU)	+= apm_emu.o
 obj-$(CONFIG_PMAC_SMU)		+= smu.o
+obj-$(CONFIG_PMAC_SMU_LED)	+= smu-led.o
 
 obj-$(CONFIG_ADB)		+= adb.o
 obj-$(CONFIG_ADB_MACII)		+= via-macii.o
diff -Nrup --exclude-from linux-exclude-from linux-2.6.19.1.orig/drivers/macintosh/smu-led.c linux-2.6.19.1/drivers/macintosh/smu-led.c
--- linux-2.6.19.1.orig/drivers/macintosh/smu-led.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.19.1/drivers/macintosh/smu-led.c	2007-01-14 14:25:03.000000000 +0100
@@ -0,0 +1,132 @@
+/*
+ * smu LED class device
+ *
+ * Copyright 2006, 2007 Michael Hanselmann <[email-masked]>
+ *
+ * This code is based upon via-pmu-led, written by Johannes Berg, and a sample
+ * program written by Benjamin Herrenschmidt.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/leds.h>
+#include <linux/spinlock.h>
+#include <asm/smu.h>
+
+static DEFINE_SPINLOCK(lock);
+static struct smu_simple_cmd cmd;
+static unsigned char cmd_value;
+static int wanted = -1;
+
+static void __smu_led_set(struct led_classdev*, unsigned char);
+
+static void smu_led_done(struct smu_cmd *cmd, void *misc)
+{
+	struct led_classdev *led_cdev = misc;
+
+	if (cmd->status) {
+		printk(KERN_ERR "smu-led: SMU command failed\n");
+	}
+
+	spin_lock(&lock);
+
+	if (wanted != -1) {
+		if (cmd_value == wanted)
+			wanted = -1;
+		else
+			__smu_led_set(led_cdev, wanted);
+	}
+
+	spin_unlock(&lock);
+}
+
+/* Call with lock held */
+static void __smu_led_set(struct led_classdev *led_cdev,
+		unsigned char value)
+{
+	int rc;
+
+	cmd_value = value;
+	rc = smu_queue_simple(&cmd, SMU_CMD_MISC_ee_COMMAND, 3,
+		smu_led_done, led_cdev,
+		SMU_CMD_MISC_ee_LEDS_CTRL, 0x00, value);
+	if (rc) {
+		printk(KERN_ERR "smu-led: "
+			"Command queueing failed, error %d\n", rc);
+	}
+}
+
+static void smu_led_set(struct led_classdev *led_cdev,
+		enum led_brightness brightness)
+{
+	unsigned char value;
+
+	/* Setting the LED to its default half bright status isn't possible
+	 * yet. Reason is that we don't know for sure how to do it.
+	 */
+
+	switch (brightness) {
+	case LED_OFF:
+		value = 0x00;
+		break;
+
+	case LED_FULL:
+		value = 0x01;
+		break;
+
+	default:
+		/* Unknown brightness, do nothing */
+		return;
+	}
+
+	spin_lock(&lock);
+
+	if (wanted == -1) {
+		wanted = value;
+		__smu_led_set(led_cdev, value);
+	} else
+		wanted = value;
+
+	spin_unlock(&lock);
+}
+
+static struct led_classdev smu_led = {
+	.name = "smu-front-led",
+	.brightness_set = smu_led_set,
+};
+
+static int __init smu_led_init(void)
+{
+	if (!smu_present())
+		return -ENODEV;
+
+	return led_classdev_register(NULL, &smu_led);
+}
+
+static void __exit smu_led_exit(void)
+{
+	led_classdev_unregister(&smu_led);
+}
+
+module_init(smu_led_init);
+module_exit(smu_led_exit);
+
+MODULE_AUTHOR("Michael Hanselmann <[email-masked]>");
+MODULE_DESCRIPTION("Front LED support for SMU based PowerMacs");
+MODULE_LICENSE("GPL");