[Lguest] RTC for lguest
Grant Grundler
grundler at parisc-linux.org
Sun Mar 2 05:04:38 EST 2008
Rusty,
Thanks again for the lguest tutorial at lca2008.
Patch below adds a RTC driver that provides minimal functionality
for lguest. I've only tested 2.6.23 under Qemu if that matters.
In general, I think the rtc-lguest has to treat the host as a
read-only HW clock and any additional features being added
need to keep that in mind.
I'm not certain I have the Kconfig entry quite right but it
works for me. Would be nice if someone with Kbuild-fu would
take a quick look at it. I didn't really want "tristate"
since it should not be a module if LGUEST is enabled.
But if the kernel is being booted as a "host", I don't want
rtc-lguest enabled either....suggests a run-time check is needed
since we don't want to displace what normally would be /dev/rtc0.
enjoy!
grant
Signed-off-by: Grant Grundler <grundler at parisc-linux.org>
--- linux-2.6.23/drivers/rtc/Kconfig-ORIG 2008-02-03 23:20:09.000000000 +1100
+++ linux-2.6.23/drivers/rtc/Kconfig 2008-02-04 16:54:51.000000000 +1100
@@ -117,6 +117,16 @@
This driver can also be built as a module. If so, the module
will be called rtc-test.
+config RTC_DRV_LGUEST
+ tristate "Lguest RTC psuedo-device"
+ default LGUEST
+ help
+ If you say yes, you get /dev/rtc support for Lguest.
+ This psuedo driver provides a fake RTC to the guest by
+ communicating with the host. In effect, the host is a
+ read-only "real time" clock source.
+ This driver will automatically be selected if LGUEST is enabled.
+
comment "I2C RTC drivers"
depends on I2C
--- linux-2.6.23/drivers/rtc/Makefile-ORIG 2008-02-03 23:20:29.000000000 +1100
+++ linux-2.6.23/drivers/rtc/Makefile 2008-02-03 23:37:44.000000000 +1100
@@ -28,6 +28,7 @@
obj-$(CONFIG_RTC_DRV_DS1742) += rtc-ds1742.o
obj-$(CONFIG_RTC_DRV_EP93XX) += rtc-ep93xx.o
obj-$(CONFIG_RTC_DRV_ISL1208) += rtc-isl1208.o
+obj-$(CONFIG_RTC_DRV_LGUEST) += rtc-lguest.o
obj-$(CONFIG_RTC_DRV_M41T80) += rtc-m41t80.o
obj-$(CONFIG_RTC_DRV_M48T59) += rtc-m48t59.o
obj-$(CONFIG_RTC_DRV_M48T86) += rtc-m48t86.o
--- /dev/null 2008-02-06 20:05:08.534205825 +1100
+++ linux-2.6.23/drivers/rtc/rtc-lguest.c 2008-02-06 20:13:53.000000000 +1100
@@ -0,0 +1,215 @@
+/*
+ * An lguest RTC device/driver
+ * Copyright (C) 2008 Grant Grundler <grundler at parisc-linux.org>
+ *
+ * This driver only happened because "Rusty" Russell gave an lguest
+ * tutorial at LCA2008. Thanks Rusty!
+ *
+ * General framework borrowed from rtc-test.c:
+ * Original Author: Alessandro Zummo <a.zummo at towertech.it>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+#include <linux/lguest.h> /* for hcall() proto */
+
+static struct platform_device *lg_rtc0;
+
+#define ENABLE_RTC_ALARM 0
+#if ENABLE_RTC_ALARM
+static int lguest_rtc_read_alarm(struct device *dev,
+ struct rtc_wkalrm *alrm)
+{
+ /* FIXME: probably want to make an hcall() here instead */
+ return 0;
+}
+
+static int lguest_rtc_set_alarm(struct device *dev,
+ struct rtc_wkalrm *alrm)
+{
+ /* FIXME: probably want to make an hcall() here instead */
+ return 0;
+}
+#endif
+
+static int lguest_rtc_read_time(struct device *dev,
+ struct rtc_time *tm)
+{
+#if 1
+ rtc_time_to_tm(get_seconds(), tm);
+#else
+#error FIXME - add hcall to ask host the time.
+#endif
+ return 0;
+}
+
+static int lguest_rtc_set_time(struct device *dev,
+ struct rtc_time *tm)
+{
+ return 0; /* guests not permitted to set the time */
+}
+
+static int lguest_rtc_set_mmss(struct device *dev, unsigned long secs)
+{
+ return 0;
+}
+
+static int lguest_rtc_proc(struct device *dev, struct seq_file *seq)
+{
+ struct platform_device *plat_dev = to_platform_device(dev);
+
+ seq_printf(seq, "lg_rtc\t\t: yes\n");
+ seq_printf(seq, "id\t\t: %d\n", plat_dev->id);
+
+ return 0;
+}
+
+static int lguest_rtc_ioctl(struct device *dev, unsigned int cmd,
+ unsigned long arg)
+{
+ switch (cmd) {
+ case RTC_PIE_ON:
+ case RTC_PIE_OFF:
+ case RTC_UIE_ON:
+ case RTC_UIE_OFF:
+ case RTC_AIE_ON:
+ case RTC_AIE_OFF:
+ return 0;
+
+ default:
+ return -ENOIOCTLCMD;
+ }
+}
+
+static const struct rtc_class_ops lguest_rtc_ops = {
+ .proc = lguest_rtc_proc,
+ .read_time = lguest_rtc_read_time,
+ .set_time = lguest_rtc_set_time,
+#if ENABLE_RTC_ALARM
+ .read_alarm = lguest_rtc_read_alarm,
+ .set_alarm = lguest_rtc_set_alarm,
+#endif
+ .set_mmss = lguest_rtc_set_mmss,
+ .ioctl = lguest_rtc_ioctl,
+};
+
+static ssize_t lguest_irq_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "%d\n", 42);
+}
+
+static ssize_t lguest_irq_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int retval;
+ struct platform_device *plat_dev = to_platform_device(dev);
+ struct rtc_device *rtc = platform_get_drvdata(plat_dev);
+
+ retval = count;
+ local_irq_disable();
+ if (strncmp(buf, "tick", 4) == 0)
+ rtc_update_irq(rtc, 1, RTC_PF | RTC_IRQF);
+ else if (strncmp(buf, "alarm", 5) == 0)
+ rtc_update_irq(rtc, 1, RTC_AF | RTC_IRQF);
+ else if (strncmp(buf, "update", 6) == 0)
+ rtc_update_irq(rtc, 1, RTC_UF | RTC_IRQF);
+ else
+ retval = -EINVAL;
+ local_irq_enable();
+
+ return retval;
+}
+static DEVICE_ATTR(irq, S_IRUGO | S_IWUSR, lguest_irq_show, lguest_irq_store);
+
+static int lguest_probe(struct platform_device *plat_dev)
+{
+ int err;
+ struct rtc_device *rtc;
+
+ rtc = rtc_device_register("rtc-lguest", &plat_dev->dev,
+ &lguest_rtc_ops, THIS_MODULE);
+ if (IS_ERR(rtc)) {
+ err = PTR_ERR(rtc);
+ return err;
+ }
+
+ err = device_create_file(&plat_dev->dev, &dev_attr_irq);
+ if (err)
+ goto err;
+
+ platform_set_drvdata(plat_dev, rtc);
+
+ return 0;
+
+err:
+ rtc_device_unregister(rtc);
+ return err;
+}
+
+static int __devexit lguest_remove(struct platform_device *plat_dev)
+{
+ struct rtc_device *rtc = platform_get_drvdata(plat_dev);
+
+ rtc_device_unregister(rtc);
+ device_remove_file(&plat_dev->dev, &dev_attr_irq);
+
+ return 0;
+}
+
+static struct platform_driver lguest_drv = {
+ .probe = lguest_probe,
+ .remove = __devexit_p(lguest_remove),
+ .driver = {
+ .name = "rtc-lguest",
+ .owner = THIS_MODULE,
+ },
+};
+
+static int __init lguest_init(void)
+{
+ int err;
+
+ err = platform_driver_register(&lguest_drv);
+ if (err)
+ return err;
+
+ lg_rtc0 = platform_device_alloc("rtc-lguest", 0);
+ if (lg_rtc0 == NULL) {
+ err = -ENOMEM;
+ goto exit_driver_unregister;
+ }
+
+ err = platform_device_add(lg_rtc0);
+ if (err)
+ goto exit_free_rtc0;
+
+ return 0;
+
+exit_free_rtc0:
+ platform_device_put(lg_rtc0);
+
+exit_driver_unregister:
+ platform_driver_unregister(&lguest_drv);
+ return err;
+}
+
+static void __exit lguest_exit(void)
+{
+ platform_device_unregister(lg_rtc0);
+ platform_driver_unregister(&lguest_drv);
+}
+
+MODULE_AUTHOR("Grant Grundler <grundler at parisc-linux.org>");
+MODULE_DESCRIPTION("lguest RTC driver");
+MODULE_LICENSE("GPL");
+
+module_init(lguest_init);
+module_exit(lguest_exit);
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