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Subject[PATCH] firewire: cdev: add more flexible cycle timer ioctl
The system time from CLOCK_REALTIME is not monotonic, hence problematic
for the main user of the FW_CDEV_IOC_GET_CYCLE_TIMER ioctl. This issue
exists in its successor ABI, i.e. raw1394, too.
http://subversion.ffado.org/ticket/242

We now offer an alternative ioctl which lets the caller choose between
CLOCK_REALTIME, CLOCK_MONOTONIC, and CLOCK_MONOTONIC_RAW as source of
the local time, very similar to the clock_gettime libc function. The
format of the local time return value matches that of clock_gettime
(seconds and nanoseconds, instead of a single microseconds value from
the existing ioctl).

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
---
drivers/firewire/core-cdev.c | 37 ++++++++++++++++++++++++++++------
include/linux/firewire-cdev.h | 31 +++++++++++++++++++++++++---
2 files changed, 58 insertions(+), 10 deletions(-)
Index: b/drivers/firewire/core-cdev.c
===================================================================
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -1030,22 +1030,46 @@ static int ioctl_stop_iso(struct client
return fw_iso_context_stop(client->iso_context);
}

-static int ioctl_get_cycle_timer(struct client *client, void *buffer)
+static int ioctl_get_cycle_timer2(struct client *client, void *buffer)
{
- struct fw_cdev_get_cycle_timer *request = buffer;
+ struct fw_cdev_get_cycle_timer2 *request = buffer;
struct fw_card *card = client->device->card;
- struct timeval tv;
+ struct timespec ts = {0, 0};
u32 cycle_time;
+ int ret = 0;

local_irq_disable();

cycle_time = card->driver->get_cycle_time(card);
- do_gettimeofday(&tv);
+
+ switch (request->clk_id) {
+ case CLOCK_REALTIME: getnstimeofday(&ts); break;
+ case CLOCK_MONOTONIC: do_posix_clock_monotonic_gettime(&ts); break;
+ case CLOCK_MONOTONIC_RAW: getrawmonotonic(&ts); break;
+ default:
+ ret = -EINVAL;
+ }

local_irq_enable();

- request->local_time = tv.tv_sec * 1000000ULL + tv.tv_usec;
- request->cycle_timer = cycle_time;
+ request->tv_sec = ts.tv_sec;
+ request->tv_nsec = ts.tv_nsec;
+ request->cycle_timer = cycle_time;
+
+ return ret;
+}
+
+static int ioctl_get_cycle_timer(struct client *client, void *buffer)
+{
+ struct fw_cdev_get_cycle_timer *request = buffer;
+ struct fw_cdev_get_cycle_timer2 ct2;
+
+ ct2.clk_id = CLOCK_REALTIME;
+ ioctl_get_cycle_timer2(client, &ct2);
+
+ request->local_time = ct2.tv_sec * USEC_PER_SEC +
+ ct2.tv_nsec / NSEC_PER_USEC;
+ request->cycle_timer = ct2.cycle_timer;

return 0;
}
@@ -1319,6 +1343,7 @@ static int (* const ioctl_handlers[])(st
ioctl_get_speed,
ioctl_send_broadcast_request,
ioctl_send_stream_packet,
+ ioctl_get_cycle_timer2,
};

static int dispatch_ioctl(struct client *client,
Index: b/include/linux/firewire-cdev.h
===================================================================
--- a/include/linux/firewire-cdev.h
+++ b/include/linux/firewire-cdev.h
@@ -248,6 +248,9 @@ union fw_cdev_event {
#define FW_CDEV_IOC_SEND_BROADCAST_REQUEST _IOW('#', 0x12, struct fw_cdev_send_request)
#define FW_CDEV_IOC_SEND_STREAM_PACKET _IOW('#', 0x13, struct fw_cdev_send_stream_packet)

+/* available since kernel version 2.6.34 */
+#define FW_CDEV_IOC_GET_CYCLE_TIMER2 _IOWR('#', 0x14, struct fw_cdev_get_cycle_timer2)
+
/*
* FW_CDEV_VERSION History
* 1 (2.6.22) - initial version
@@ -544,14 +547,15 @@ struct fw_cdev_stop_iso {
/**
* struct fw_cdev_get_cycle_timer - read cycle timer register
* @local_time: system time, in microseconds since the Epoch
- * @cycle_timer: isochronous cycle timer, as per OHCI 1.1 clause 5.13
+ * @cycle_timer: Cycle Time register contents
*
* The %FW_CDEV_IOC_GET_CYCLE_TIMER ioctl reads the isochronous cycle timer
- * and also the system clock. This allows to express the receive time of an
- * isochronous packet as a system time with microsecond accuracy.
+ * and also the system clock (%CLOCK_REALTIME). This allows to express the
+ * receive time of an isochronous packet as a system time.
*
* @cycle_timer consists of 7 bits cycleSeconds, 13 bits cycleCount, and
- * 12 bits cycleOffset, in host byte order.
+ * 12 bits cycleOffset, in host byte order. Cf. the Cycle Time register
+ * per IEEE 1394 or Isochronous Cycle Timer register per OHCI-1394.
*/
struct fw_cdev_get_cycle_timer {
__u64 local_time;
@@ -559,6 +563,25 @@ struct fw_cdev_get_cycle_timer {
};

/**
+ * struct fw_cdev_get_cycle_timer2 - read cycle timer register
+ * @tv_sec: system time, seconds
+ * @tv_nsec: system time, sub-seconds part in nanoseconds
+ * @clk_id: input parameter, clock from which to get the system time
+ * @cycle_timer: Cycle Time register contents
+ *
+ * The %FW_CDEV_IOC_GET_CYCLE_TIMER2 works like
+ * %FW_CDEV_IOC_GET_CYCLE_TIMER but lets you choose a clock like with POSIX'
+ * clock_gettime function. Supported @clk_id values are POSIX' %CLOCK_REALTIME
+ * and %CLOCK_MONOTONIC and Linux' %CLOCK_MONOTONIC_RAW.
+ */
+struct fw_cdev_get_cycle_timer2 {
+ __s64 tv_sec;
+ __s32 tv_nsec;
+ __s32 clk_id;
+ __u32 cycle_timer;
+};
+
+/**
* struct fw_cdev_allocate_iso_resource - (De)allocate a channel or bandwidth
* @closure: Passed back to userspace in correponding iso resource events
* @channels: Isochronous channels of which one is to be (de)allocated
--
Stefan Richter
-=====-==-=- --=- =--==
http://arcgraph.de/sr/


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