[POWERPC] Xserve cpu-meter driver

This is a small driver for the Xserve G5 CPU-meter blue LEDs on the
front-panel. It might work on the Xserve G4 as well though that was
not tested. It's pretty basic and could use some improvements if
somebody cares doing them. :)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 620 insertions, 0 deletions

diff --git a/drivers/macintosh/Kconfig b/drivers/macintosh/Kconfig
index 7f8477d3a6..92ccee85e2 100644
--- a/drivers/macintosh/Kconfig
+++ b/drivers/macintosh/Kconfig
@@ -228,4 +228,11 @@ config ANSLCD
         tristate "Support for ANS LCD display"
         depends on ADB_CUDA && PPC_PMAC
 
+config PMAC_RACKMETER
+        tristate "Support for Apple XServe front panel LEDs"
+        depends on PPC_PMAC
+        help
+          This driver procides some support to control the front panel
+          blue LEDs "vu-meter" of the XServer macs.
+
 endmenu
diff --git a/drivers/macintosh/Makefile b/drivers/macintosh/Makefile
index b53d45f87b..2dfc3f4eaf 100644
--- a/drivers/macintosh/Makefile
+++ b/drivers/macintosh/Makefile
@@ -42,3 +42,4 @@ obj-$(CONFIG_WINDFARM_PM112)	+= windfarm_pm112.o windfarm_smu_sat.o \
                                    windfarm_smu_sensors.o \
                                    windfarm_max6690_sensor.o \
                                    windfarm_lm75_sensor.o windfarm_pid.o
+obj-$(CONFIG_PMAC_RACKMETER)    += rack-meter.o
diff --git a/drivers/macintosh/rack-meter.c b/drivers/macintosh/rack-meter.c
new file mode 100644
index 0000000000..f1b6f56367
--- /dev/null
+++ b/drivers/macintosh/rack-meter.c
@@ -0,0 +1,612 @@
+/*
+ * RackMac vu-meter driver
+ *
+ * (c) Copyright 2006 Benjamin Herrenschmidt, IBM Corp.
+ *                    <benh@kernel.crashing.org>
+ *
+ * Released under the term of the GNU GPL v2.
+ *
+ * Support the CPU-meter LEDs of the Xserve G5
+ *
+ * TODO: Implement PWM to do variable intensity and provide userland
+ * interface for fun. Also, the CPU-meter could be made nicer by being
+ * a bit less "immediate" but giving instead a more average load over
+ * time. Patches welcome :-)
+ *
+ */
+#undef DEBUG
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/dma-mapping.h>
+#include <linux/kernel_stat.h>
+
+#include <asm/io.h>
+#include <asm/prom.h>
+#include <asm/machdep.h>
+#include <asm/pmac_feature.h>
+#include <asm/dbdma.h>
+#include <asm/dbdma.h>
+#include <asm/macio.h>
+#include <asm/keylargo.h>
+
+/* Number of samples in a sample buffer */
+#define SAMPLE_COUNT            256
+
+/* CPU meter sampling rate in ms */
+#define CPU_SAMPLING_RATE       250
+
+struct rackmeter_dma {
+        struct dbdma_cmd        cmd[4]                  ____cacheline_aligned;
+        u32                     mark                    ____cacheline_aligned;
+        u32                     buf1[SAMPLE_COUNT]      ____cacheline_aligned;
+        u32                     buf2[SAMPLE_COUNT]      ____cacheline_aligned;
+} ____cacheline_aligned;
+
+struct rackmeter_cpu {
+        struct work_struct      sniffer;
+        cputime64_t             prev_wall;
+        cputime64_t             prev_idle;
+        int                     zero;
+} ____cacheline_aligned;
+
+struct rackmeter {
+        struct macio_dev                *mdev;
+        unsigned int                    irq;
+        struct device_node              *i2s;
+        u8                              *ubuf;
+        struct dbdma_regs __iomem       *dma_regs;
+        void __iomem                    *i2s_regs;
+        dma_addr_t                      dma_buf_p;
+        struct rackmeter_dma            *dma_buf_v;
+        int                             stale_irq;
+        struct rackmeter_cpu            cpu[2];
+        int                             paused;
+        struct mutex                    sem;
+};
+
+/* To be set as a tunable */
+static int rackmeter_ignore_nice;
+
+/* This GPIO is whacked by the OS X driver when initializing */
+#define RACKMETER_MAGIC_GPIO    0x78
+
+/* This is copied from cpufreq_ondemand, maybe we should put it in
+ * a common header somewhere
+ */
+static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
+{
+        cputime64_t retval;
+
+        retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
+                        kstat_cpu(cpu).cpustat.iowait);
+
+        if (rackmeter_ignore_nice)
+                retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
+
+        return retval;
+}
+
+static void rackmeter_setup_i2s(struct rackmeter *rm)
+{
+        struct macio_chip *macio = rm->mdev->bus->chip;
+
+        /* First whack magic GPIO */
+        pmac_call_feature(PMAC_FTR_WRITE_GPIO, NULL, RACKMETER_MAGIC_GPIO, 5);
+
+
+        /* Call feature code to enable the sound channel and the proper
+         * clock sources
+         */
+        pmac_call_feature(PMAC_FTR_SOUND_CHIP_ENABLE, rm->i2s, 0, 1);
+
+        /* Power i2s and stop i2s clock. We whack MacIO FCRs directly for now.
+         * This is a bit racy, thus we should add new platform functions to
+         * handle that. snd-aoa needs that too
+         */
+        MACIO_BIS(KEYLARGO_FCR1, KL1_I2S0_ENABLE);
+        MACIO_BIC(KEYLARGO_FCR1, KL1_I2S0_CLK_ENABLE_BIT);
+        (void)MACIO_IN32(KEYLARGO_FCR1);
+        udelay(10);
+
+        /* Then setup i2s. For now, we use the same magic value that
+         * the OS X driver seems to use. We might want to play around
+         * with the clock divisors later
+         */
+        out_le32(rm->i2s_regs + 0x10, 0x01fa0000);
+        (void)in_le32(rm->i2s_regs + 0x10);
+        udelay(10);
+
+        /* Fully restart i2s*/
+        MACIO_BIS(KEYLARGO_FCR1, KL1_I2S0_CELL_ENABLE |
+                  KL1_I2S0_CLK_ENABLE_BIT);
+        (void)MACIO_IN32(KEYLARGO_FCR1);
+        udelay(10);
+}
+
+static void rackmeter_set_default_pattern(struct rackmeter *rm)
+{
+        int i;
+
+        for (i = 0; i < 16; i++) {
+                if (i < 8)
+                        rm->ubuf[i] = (i & 1) * 255;
+                else
+                        rm->ubuf[i] = ((~i) & 1) * 255;
+        }
+}
+
+static void rackmeter_do_pause(struct rackmeter *rm, int pause)
+{
+        struct rackmeter_dma *rdma = rm->dma_buf_v;
+
+        pr_debug("rackmeter: %s\n", pause ? "paused" : "started");
+
+        rm->paused = pause;
+        if (pause) {
+                DBDMA_DO_STOP(rm->dma_regs);
+                return;
+        }
+        memset(rdma->buf1, 0, SAMPLE_COUNT & sizeof(u32));
+        memset(rdma->buf2, 0, SAMPLE_COUNT & sizeof(u32));
+
+        rm->dma_buf_v->mark = 0;
+
+        mb();
+        out_le32(&rm->dma_regs->cmdptr_hi, 0);
+        out_le32(&rm->dma_regs->cmdptr, rm->dma_buf_p);
+        out_le32(&rm->dma_regs->control, (RUN << 16) | RUN);
+}
+
+static void rackmeter_setup_dbdma(struct rackmeter *rm)
+{
+        struct rackmeter_dma *db = rm->dma_buf_v;
+        struct dbdma_cmd *cmd = db->cmd;
+
+        /* Make sure dbdma is reset */
+        DBDMA_DO_RESET(rm->dma_regs);
+
+        pr_debug("rackmeter: mark offset=0x%lx\n",
+                 offsetof(struct rackmeter_dma, mark));
+        pr_debug("rackmeter: buf1 offset=0x%lx\n",
+                 offsetof(struct rackmeter_dma, buf1));
+        pr_debug("rackmeter: buf2 offset=0x%lx\n",
+                 offsetof(struct rackmeter_dma, buf2));
+
+        /* Prepare 4 dbdma commands for the 2 buffers */
+        memset(cmd, 0, 4 * sizeof(struct dbdma_cmd));
+        st_le16(&cmd->req_count, 4);
+        st_le16(&cmd->command, STORE_WORD | INTR_ALWAYS | KEY_SYSTEM);
+        st_le32(&cmd->phy_addr, rm->dma_buf_p +
+                offsetof(struct rackmeter_dma, mark));
+        st_le32(&cmd->cmd_dep, 0x02000000);
+        cmd++;
+
+        st_le16(&cmd->req_count, SAMPLE_COUNT * 4);
+        st_le16(&cmd->command, OUTPUT_MORE);
+        st_le32(&cmd->phy_addr, rm->dma_buf_p +
+                offsetof(struct rackmeter_dma, buf1));
+        cmd++;
+
+        st_le16(&cmd->req_count, 4);
+        st_le16(&cmd->command, STORE_WORD | INTR_ALWAYS | KEY_SYSTEM);
+        st_le32(&cmd->phy_addr, rm->dma_buf_p +
+                offsetof(struct rackmeter_dma, mark));
+        st_le32(&cmd->cmd_dep, 0x01000000);
+        cmd++;
+
+        st_le16(&cmd->req_count, SAMPLE_COUNT * 4);
+        st_le16(&cmd->command, OUTPUT_MORE | BR_ALWAYS);
+        st_le32(&cmd->phy_addr, rm->dma_buf_p +
+                offsetof(struct rackmeter_dma, buf2));
+        st_le32(&cmd->cmd_dep, rm->dma_buf_p);
+
+        rackmeter_do_pause(rm, 0);
+}
+
+static void rackmeter_do_timer(void *data)
+{
+        struct rackmeter *rm = data;
+        unsigned int cpu = smp_processor_id();
+        struct rackmeter_cpu *rcpu = &rm->cpu[cpu];
+        cputime64_t cur_jiffies, total_idle_ticks;
+        unsigned int total_ticks, idle_ticks;
+        int i, offset, load, cumm, pause;
+
+        cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
+        total_ticks = (unsigned int)cputime64_sub(cur_jiffies,
+                                                  rcpu->prev_wall);
+        rcpu->prev_wall = cur_jiffies;
+
+        total_idle_ticks = get_cpu_idle_time(cpu);
+        idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
+                                rcpu->prev_idle);
+        rcpu->prev_idle = total_idle_ticks;
+
+        /* We do a very dumb calculation to update the LEDs for now,
+         * we'll do better once we have actual PWM implemented
+         */
+        load = (9 * (total_ticks - idle_ticks)) / total_ticks;
+
+        offset = cpu << 3;
+        cumm = 0;
+        for (i = 0; i < 8; i++) {
+                u8 ub = (load > i) ? 0xff : 0;
+                rm->ubuf[i + offset] = ub;
+                cumm |= ub;
+        }
+        rcpu->zero = (cumm == 0);
+
+        /* Now check if LEDs are all 0, we can stop DMA */
+        pause = (rm->cpu[0].zero && rm->cpu[1].zero);
+        if (pause != rm->paused) {
+                mutex_lock(&rm->sem);
+                pause = (rm->cpu[0].zero && rm->cpu[1].zero);
+                rackmeter_do_pause(rm, pause);
+                mutex_unlock(&rm->sem);
+        }
+        schedule_delayed_work_on(cpu, &rcpu->sniffer,
+                                 msecs_to_jiffies(CPU_SAMPLING_RATE));
+}
+
+static void __devinit rackmeter_init_cpu_sniffer(struct rackmeter *rm)
+{
+        unsigned int cpu;
+
+        /* This driver works only with 1 or 2 CPUs numbered 0 and 1,
+         * but that's really all we have on Apple Xserve. It doesn't
+         * play very nice with CPU hotplug neither but we don't do that
+         * on those machines yet
+         */
+
+        INIT_WORK(&rm->cpu[0].sniffer, rackmeter_do_timer, rm);
+        INIT_WORK(&rm->cpu[1].sniffer, rackmeter_do_timer, rm);
+
+        for_each_online_cpu(cpu) {
+                struct rackmeter_cpu *rcpu;
+
+                if (cpu > 1)
+                        continue;
+                rcpu = &rm->cpu[cpu];;
+                rcpu->prev_idle = get_cpu_idle_time(cpu);
+                rcpu->prev_wall = jiffies64_to_cputime64(get_jiffies_64());
+                schedule_delayed_work_on(cpu, &rm->cpu[cpu].sniffer,
+                                         msecs_to_jiffies(CPU_SAMPLING_RATE));
+        }
+}
+
+static void __devexit rackmeter_stop_cpu_sniffer(struct rackmeter *rm)
+{
+        cancel_rearming_delayed_work(&rm->cpu[0].sniffer);
+        cancel_rearming_delayed_work(&rm->cpu[1].sniffer);
+}
+
+static int rackmeter_setup(struct rackmeter *rm)
+{
+        pr_debug("rackmeter: setting up i2s..\n");
+        rackmeter_setup_i2s(rm);
+
+        pr_debug("rackmeter: setting up default pattern..\n");
+        rackmeter_set_default_pattern(rm);
+
+        pr_debug("rackmeter: setting up dbdma..\n");
+        rackmeter_setup_dbdma(rm);
+
+        pr_debug("rackmeter: start CPU measurements..\n");
+        rackmeter_init_cpu_sniffer(rm);
+
+        printk(KERN_INFO "RackMeter initialized\n");
+
+        return 0;
+}
+
+/*  XXX FIXME: No PWM yet, this is 0/1 */
+static u32 rackmeter_calc_sample(struct rackmeter *rm, unsigned int index)
+{
+        int led;
+        u32 sample = 0;
+
+        for (led = 0; led < 16; led++) {
+                sample >>= 1;
+                sample |= ((rm->ubuf[led] >= 0x80) << 15);
+        }
+        return (sample << 17) | (sample >> 15);
+}
+
+static irqreturn_t rackmeter_irq(int irq, void *arg)
+{
+        struct rackmeter *rm = arg;
+        struct rackmeter_dma *db = rm->dma_buf_v;
+        unsigned int mark, i;
+        u32 *buf;
+
+        /* Flush PCI buffers with an MMIO read. Maybe we could actually
+         * check the status one day ... in case things go wrong, though
+         * this never happened to me
+         */
+        (void)in_le32(&rm->dma_regs->status);
+
+        /* Make sure the CPU gets us in order */
+        rmb();
+
+        /* Read mark */
+        mark = db->mark;
+        if (mark != 1 && mark != 2) {
+                printk(KERN_WARNING "rackmeter: Incorrect DMA mark 0x%08x\n",
+                       mark);
+                /* We allow for 3 errors like that (stale DBDMA irqs) */
+                if (++rm->stale_irq > 3) {
+                        printk(KERN_ERR "rackmeter: Too many errors,"
+                               " stopping DMA\n");
+                        DBDMA_DO_RESET(rm->dma_regs);
+                }
+                return IRQ_HANDLED;
+        }
+
+        /* Next buffer we need to fill is mark value */
+        buf = mark == 1 ? db->buf1 : db->buf2;
+
+        /* Fill it now. This routine converts the 8 bits depth sample array
+         * into the PWM bitmap for each LED.
+         */
+        for (i = 0; i < SAMPLE_COUNT; i++)
+                buf[i] = rackmeter_calc_sample(rm, i);
+
+
+        return IRQ_HANDLED;
+}
+
+static int __devinit rackmeter_probe(struct macio_dev* mdev,
+                                     const struct of_device_id *match)
+{
+        struct device_node *i2s = NULL, *np = NULL;
+        struct rackmeter *rm = NULL;
+        struct resource ri2s, rdma;
+        int rc = -ENODEV;
+
+        pr_debug("rackmeter_probe()\n");
+
+        /* Get i2s-a node */
+        while ((i2s = of_get_next_child(mdev->ofdev.node, i2s)) != NULL)
+               if (strcmp(i2s->name, "i2s-a") == 0)
+                       break;
+        if (i2s == NULL) {
+                pr_debug("  i2s-a child not found\n");
+                goto bail;
+        }
+        /* Get lightshow or virtual sound */
+        while ((np = of_get_next_child(i2s, np)) != NULL) {
+               if (strcmp(np->name, "lightshow") == 0)
+                       break;
+               if ((strcmp(np->name, "sound") == 0) &&
+                   get_property(np, "virtual", NULL) != NULL)
+                       break;
+        }
+        if (np == NULL) {
+                pr_debug("  lightshow or sound+virtual child not found\n");
+                goto bail;
+        }
+
+        /* Create and initialize our instance data */
+        rm = kzalloc(sizeof(struct rackmeter), GFP_KERNEL);
+        if (rm == NULL) {
+                printk(KERN_ERR "rackmeter: failed to allocate memory !\n");
+                rc = -ENOMEM;
+                goto bail_release;
+        }
+        rm->mdev = mdev;
+        rm->i2s = i2s;
+        mutex_init(&rm->sem);
+        dev_set_drvdata(&mdev->ofdev.dev, rm);
+        /* Check resources availability. We need at least resource 0 and 1 */
+#if 0 /* Use that when i2s-a is finally an mdev per-se */
+        if (macio_resource_count(mdev) < 2 || macio_irq_count(mdev) < 2) {
+                printk(KERN_ERR
+                       "rackmeter: found match but lacks resources: %s"
+                       " (%d resources, %d interrupts)\n",
+                       mdev->ofdev.node->full_name);
+                rc = -ENXIO;
+                goto bail_free;
+        }
+        if (macio_request_resources(mdev, "rackmeter")) {
+                printk(KERN_ERR
+                       "rackmeter: failed to request resources: %s\n",
+                       mdev->ofdev.node->full_name);
+                rc = -EBUSY;
+                goto bail_free;
+        }
+        rm->irq = macio_irq(mdev, 1);
+#else
+        rm->irq = irq_of_parse_and_map(i2s, 1);
+        if (rm->irq == NO_IRQ ||
+            of_address_to_resource(i2s, 0, &ri2s) ||
+            of_address_to_resource(i2s, 1, &rdma)) {
+                printk(KERN_ERR
+                       "rackmeter: found match but lacks resources: %s",
+                       mdev->ofdev.node->full_name);
+                rc = -ENXIO;
+                goto bail_free;
+        }
+#endif
+
+        pr_debug("  i2s @0x%08x\n", (unsigned int)ri2s.start);
+        pr_debug("  dma @0x%08x\n", (unsigned int)rdma.start);
+        pr_debug("  irq %d\n", rm->irq);
+
+        rm->ubuf = (u8 *)__get_free_page(GFP_KERNEL);
+        if (rm->ubuf == NULL) {
+                printk(KERN_ERR
+                       "rackmeter: failed to allocate samples page !\n");
+                rc = -ENOMEM;
+                goto bail_release;
+        }
+
+        rm->dma_buf_v = dma_alloc_coherent(&macio_get_pci_dev(mdev)->dev,
+                                           sizeof(struct rackmeter_dma),
+                                           &rm->dma_buf_p, GFP_KERNEL);
+        if (rm->dma_buf_v == NULL) {
+                printk(KERN_ERR
+                       "rackmeter: failed to allocate dma buffer !\n");
+                rc = -ENOMEM;
+                goto bail_free_samples;
+        }
+#if 0
+        rm->i2s_regs = ioremap(macio_resource_start(mdev, 0), 0x1000);
+#else
+        rm->i2s_regs = ioremap(ri2s.start, 0x1000);
+#endif
+        if (rm->i2s_regs == NULL) {
+                printk(KERN_ERR
+                       "rackmeter: failed to map i2s registers !\n");
+                rc = -ENXIO;
+                goto bail_free_dma;
+        }
+#if 0
+        rm->dma_regs = ioremap(macio_resource_start(mdev, 1), 0x100);
+#else
+        rm->dma_regs = ioremap(rdma.start, 0x100);
+#endif
+        if (rm->dma_regs == NULL) {
+                printk(KERN_ERR
+                       "rackmeter: failed to map dma registers !\n");
+                rc = -ENXIO;
+                goto bail_unmap_i2s;
+        }
+
+        rc = rackmeter_setup(rm);
+        if (rc) {
+                printk(KERN_ERR
+                       "rackmeter: failed to initialize !\n");
+                rc = -ENXIO;
+                goto bail_unmap_dma;
+        }
+
+        rc = request_irq(rm->irq, rackmeter_irq, 0, "rackmeter", rm);
+        if (rc != 0) {
+                printk(KERN_ERR
+                       "rackmeter: failed to request interrupt !\n");
+                goto bail_stop_dma;
+        }
+        of_node_put(np);
+        return 0;
+
+ bail_stop_dma:
+        DBDMA_DO_RESET(rm->dma_regs);
+ bail_unmap_dma:
+        iounmap(rm->dma_regs);
+ bail_unmap_i2s:
+        iounmap(rm->i2s_regs);
+ bail_free_dma:
+        dma_free_coherent(&macio_get_pci_dev(mdev)->dev,
+                          sizeof(struct rackmeter_dma),
+                          rm->dma_buf_v, rm->dma_buf_p);
+ bail_free_samples:
+        free_page((unsigned long)rm->ubuf);
+ bail_release:
+#if 0
+        macio_release_resources(mdev);
+#endif
+ bail_free:
+        kfree(rm);
+ bail:
+        of_node_put(i2s);
+        of_node_put(np);
+        dev_set_drvdata(&mdev->ofdev.dev, NULL);
+        return rc;
+}
+
+static int __devexit rackmeter_remove(struct macio_dev* mdev)
+{
+        struct rackmeter *rm = dev_get_drvdata(&mdev->ofdev.dev);
+
+        /* Stop CPU sniffer timer & work queues */
+        rackmeter_stop_cpu_sniffer(rm);
+
+        /* Clear reference to private data */
+        dev_set_drvdata(&mdev->ofdev.dev, NULL);
+
+        /* Stop/reset dbdma */
+        DBDMA_DO_RESET(rm->dma_regs);
+
+        /* Release the IRQ */
+        free_irq(rm->irq, rm);
+
+        /* Unmap registers */
+        iounmap(rm->dma_regs);
+        iounmap(rm->i2s_regs);
+
+        /* Free DMA */
+        dma_free_coherent(&macio_get_pci_dev(mdev)->dev,
+                          sizeof(struct rackmeter_dma),
+                          rm->dma_buf_v, rm->dma_buf_p);
+
+        /* Free samples */
+        free_page((unsigned long)rm->ubuf);
+
+#if 0
+        /* Release resources */
+        macio_release_resources(mdev);
+#endif
+
+        /* Get rid of me */
+        kfree(rm);
+
+        return 0;
+}
+
+static int rackmeter_shutdown(struct macio_dev* mdev)
+{
+        struct rackmeter *rm = dev_get_drvdata(&mdev->ofdev.dev);
+
+        if (rm == NULL)
+                return -ENODEV;
+
+        /* Stop CPU sniffer timer & work queues */
+        rackmeter_stop_cpu_sniffer(rm);
+
+        /* Stop/reset dbdma */
+        DBDMA_DO_RESET(rm->dma_regs);
+
+        return 0;
+}
+
+static struct of_device_id rackmeter_match[] = {
+        { .name = "i2s" },
+        { }
+};
+
+static struct macio_driver rackmeter_drv = {
+        .name = "rackmeter",
+        .owner = THIS_MODULE,
+        .match_table = rackmeter_match,
+        .probe = rackmeter_probe,
+        .remove = rackmeter_remove,
+        .shutdown = rackmeter_shutdown,
+};
+
+
+static int __init rackmeter_init(void)
+{
+        pr_debug("rackmeter_init()\n");
+
+        return macio_register_driver(&rackmeter_drv);
+}
+
+static void __exit rackmeter_exit(void)
+{
+        pr_debug("rackmeter_exit()\n");
+
+        macio_unregister_driver(&rackmeter_drv);
+}
+
+module_init(rackmeter_init);
+module_exit(rackmeter_exit);
+
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Benjamin Herrenschmidt <benh@kernel.crashing.org>");
+MODULE_DESCRIPTION("RackMeter: Support vu-meter on XServe front panel");