Re: [PATCH] Input: Add support for CLOCK_BOOTTIME

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Aniroop,

On Tue, Dec 16, 2014 at 10:26:34PM +0530, Aniroop Mathur wrote:
> This patch adds support for CLOCK_BOOTTIME for input event timestamp.
> CLOCK_BOOTTIME includes suspend time, so it would allow aplications
> to get correct time difference between two events even when system
> resumes from suspend state.
> 
> Signed-off-by: Aniroop Mathur <a.mathur@samsung.com>
> ---
>  drivers/input/evdev.c | 33 +++++++++++++++++++++------------
>  1 file changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index de05545..7825794 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -28,6 +28,13 @@
>  #include <linux/cdev.h>
>  #include "input-compat.h"
>  
> +enum clock_type {
> +	REAL = 0,
> +	MONO,
> +	BOOT,
> +	CLK_MAX
> +};
> +
>  struct evdev {
>  	int open;
>  	struct input_handle handle;
> @@ -108,8 +115,9 @@ static void evdev_queue_syn_dropped(struct evdev_client *client)
>  	struct input_event ev;
>  	ktime_t time;
>  
> -	time = (client->clkid == CLOCK_MONOTONIC) ?
> -		ktime_get() : ktime_get_real();
> +	time = (client->clkid == CLOCK_REALTIME) ?
> +		ktime_get_real() : (client->clkid == CLOCK_MONOTONIC) ?
> +		ktime_get() : ktime_get_boottime();
>  
>  	ev.time = ktime_to_timeval(time);
>  	ev.type = EV_SYN;
> @@ -159,7 +167,7 @@ static void __pass_event(struct evdev_client *client,
>  
>  static void evdev_pass_values(struct evdev_client *client,
>  			const struct input_value *vals, unsigned int count,
> -			ktime_t mono, ktime_t real)
> +			ktime_t *ev_time)
>  {
>  	struct evdev *evdev = client->evdev;
>  	const struct input_value *v;
> @@ -169,8 +177,9 @@ static void evdev_pass_values(struct evdev_client *client,
>  	if (client->revoked)
>  		return;
>  
> -	event.time = ktime_to_timeval(client->clkid == CLOCK_MONOTONIC ?
> -				      mono : real);
> +	event.time = ktime_to_timeval(client->clkid == CLOCK_REALTIME ?
> +			ev_time[REAL] : client->clkid == CLOCK_MONOTONIC ?
> +			ev_time[MONO] : ev_time[BOOT]);

This becomes unwieldy. Should we have client->clk_type instead of
client->clkid and convert CLOCK_* into your EVDEV_CLK_{REAL|MONO|BOOT}
when setting it in ioctl and then do

	event.time = ktime_to_timeval(ev_time[client->clk_offset]);

>  
>  	/* Interrupts are disabled, just acquire the lock. */
>  	spin_lock(&client->buffer_lock);
> @@ -198,21 +207,21 @@ static void evdev_events(struct input_handle *handle,
>  {
>  	struct evdev *evdev = handle->private;
>  	struct evdev_client *client;
> -	ktime_t time_mono, time_real;
> +	ktime_t ev_time[CLK_MAX];
>  
> -	time_mono = ktime_get();
> -	time_real = ktime_mono_to_real(time_mono);
> +	ev_time[MONO] = ktime_get();
> +	ev_time[REAL] = ktime_mono_to_real(ev_time[MONO]);
> +	ev_time[BOOT] = ktime_get_boottime();

I do not think we want to use ktime_get_boottime() here; I'd rather you
use ktime_mono_to_anY(ev_time[MONO], TK_OFFS_BOOT) so that all 3 times
are consistent.

>  
>  	rcu_read_lock();
>  
>  	client = rcu_dereference(evdev->grab);
>  
>  	if (client)
> -		evdev_pass_values(client, vals, count, time_mono, time_real);
> +		evdev_pass_values(client, vals, count, ev_time);
>  	else
>  		list_for_each_entry_rcu(client, &evdev->client_list, node)
> -			evdev_pass_values(client, vals, count,
> -					  time_mono, time_real);
> +			evdev_pass_values(client, vals, count, ev_time);
>  
>  	rcu_read_unlock();
>  }
> @@ -874,7 +883,7 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
>  	case EVIOCSCLOCKID:
>  		if (copy_from_user(&i, p, sizeof(unsigned int)))
>  			return -EFAULT;
> -		if (i != CLOCK_MONOTONIC && i != CLOCK_REALTIME)
> +		if (i != CLOCK_MONOTONIC && i != CLOCK_REALTIME && i != CLOCK_BOOTTIME)
>  			return -EINVAL;
>  		client->clkid = i;
>  		return 0;
> -- 
> 1.9.1
> 

Thanks.

-- 
Dmitry