Re: [PATCH v2 1/4] uinput: Add ioctl for using monotonic/ boot times

Peter Hutterer
2016-10-27T01:45:20Z

On Mon, Oct 17, 2016 at 08:27:30PM -0700, Deepa Dinamani wrote:
> struct timeval which is part of struct input_event to
> maintain the event times is not y2038 safe.
>
> Real time timestamps are also not ideal for input_event
> as this time can go backwards as noted in the patch
> a80b83b7b8 by John Stultz.
>
> Arnd Bergmann suggested deprecating real time and using
> monotonic or other timers for all input_event times as a
> solution to both the above problems.
>
> Add a new ioctl to let the user dictate the kind of time
> to be used for input events. This is similar to the evdev
> implementation of the feature. Realtime is still the
> default time. This is to maintain backward compatibility.
>
> The structure to maintain input events will be changed
> in a different patch.
>
> Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
> ---
> drivers/input/misc/uinput.c | 56 ++++++++++++++++++++++++++++++++++++++++++++-
> include/linux/uinput.h | 1 +
> include/uapi/linux/uinput.h | 3 +++
> 3 files changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
> index 92595b9..3d75c5a 100644
> --- a/drivers/input/misc/uinput.c
> +++ b/drivers/input/misc/uinput.c
> @@ -46,11 +46,26 @@ static int uinput_dev_event(struct input_dev *dev,
> unsigned int type, unsigned int code, int value)
> {
> struct uinput_device *udev = input_get_drvdata(dev);
> + struct timespec64 ts;
>
> udev->buff[udev->head].type = type;
> udev->buff[udev->head].code = code;
> udev->buff[udev->head].value = value;
> - do_gettimeofday(&udev->buff[udev->head].time);
> +
> + switch (udev->clk_type) {
> + case CLOCK_REALTIME:
> + ktime_get_real_ts64(&ts);
> + break;
> + case CLOCK_MONOTONIC:
> + ktime_get_ts64(&ts);
> + break;
> + case CLOCK_BOOTTIME:
> + get_monotonic_boottime64(&ts);
> + break;
> + }

hmm, I'm a bit confused here. This is an in-kernel bit only (passing the
time through uinput events has no effect). So why do we need an ioctl here?
it's an in-kernel decision only anyway and the time in the events sent to
the evdev client should be dictated by what that client sets for the clock
type, right?

Cheers,
Peter

> +
> + udev->buff[udev->head].time.tv_sec = ts.tv_sec;
> + udev->buff[udev->head].time.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
> udev->head = (udev->head + 1) % UINPUT_BUFFER_SIZE;
>
> wake_up_interruptible(&udev->waitq);
> @@ -295,6 +310,7 @@ static int uinput_create_device(struct uinput_device *udev)
> if (error)
> goto fail2;
>
> + udev->clk_type = CLOCK_REALTIME;
> udev->state = UIST_CREATED;
>
> return 0;
> @@ -304,6 +320,38 @@ static int uinput_create_device(struct uinput_device *udev)
> return error;
> }
>
> +static int uinput_set_clk_type(struct uinput_device *udev, unsigned int clkid)
> +{
> + unsigned int clk_type;
> +
> + if (udev->state != UIST_CREATED)
> + return -EINVAL;
> +
> + switch (clkid) {
> + /* Realtime clock is only valid until year 2038.*/
> + case CLOCK_REALTIME:
> + clk_type = CLOCK_REALTIME;
> + break;
> + case CLOCK_MONOTONIC:
> + clk_type = CLOCK_MONOTONIC;
> + break;
> + case CLOCK_BOOTTIME:
> + clk_type = CLOCK_BOOTTIME;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + if (udev->clk_type != clk_type) {
> + udev->clk_type = clk_type;
> +
> + /* Flush pending events */
> + uinput_flush_requests(udev);
> + }
> +
> + return 0;
> +}
> +
> static int uinput_open(struct inode *inode, struct file *file)
> {
> struct uinput_device *newdev;
> @@ -787,6 +835,7 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
> char *phys;
> const char *name;
> unsigned int size;
> + int clock_id;
>
> retval = mutex_lock_interruptible(&udev->mutex);
> if (retval)
> @@ -817,6 +866,11 @@ static long uinput_ioctl_handler(struct file *file, unsigned int cmd,
> retval = uinput_dev_setup(udev, p);
> goto out;
>
> + case UI_SET_CLOCKID:
> + if (copy_from_user(&clock_id, p, sizeof(unsigned int)))
> + return -EFAULT;
> + return uinput_set_clk_type(udev, clock_id);
> +
> /* UI_ABS_SETUP is handled in the variable size ioctls */
>
> case UI_SET_EVBIT:
> diff --git a/include/linux/uinput.h b/include/linux/uinput.h
> index 75de43d..6527fb7 100644
> --- a/include/linux/uinput.h
> +++ b/include/linux/uinput.h
> @@ -72,6 +72,7 @@ struct uinput_device {
> unsigned char head;
> unsigned char tail;
> struct input_event buff[UINPUT_BUFFER_SIZE];
> + int clk_type;
> unsigned int ff_effects_max;
>
> struct uinput_request *requests[UINPUT_NUM_REQUESTS];
> diff --git a/include/uapi/linux/uinput.h b/include/uapi/linux/uinput.h
> index dc652e2..d9494ae 100644
> --- a/include/uapi/linux/uinput.h
> +++ b/include/uapi/linux/uinput.h
> @@ -133,6 +133,9 @@ struct uinput_abs_setup {
> */
> #define UI_ABS_SETUP _IOW(UINPUT_IOCTL_BASE, 4, struct uinput_abs_setup)
>
> +/* Set clockid to be used for timestamps */
> +#define UI_SET_CLOCKID _IOW(UINPUT_IOCTL_BASE, 5, int)
> +
> #define UI_SET_EVBIT _IOW(UINPUT_IOCTL_BASE, 100, int)
> #define UI_SET_KEYBIT _IOW(UINPUT_IOCTL_BASE, 101, int)
> #define UI_SET_RELBIT _IOW(UINPUT_IOCTL_BASE, 102, int)
> --
> 2.7.4
>
> --
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