[LTP] [PATCH] kernel/input: fix failure on an old kernel

[Xiao Yang <yangx.jy@cn.fujitsu.com>]

Hi,

Ping :-)

Thanks,
Xiao Yang
On 2017/10/09 17:57, Xiao Yang wrote:
> On some old kernels(e.g. v2.6.32), we always triggered the following
> error when running input04 and input05:
> --------------------------------------------------------------------
> TINFO  :  Found uinput dev at /dev/uinput
> TINFO  :  Unexpected ev type=0 code=0 value=0
> TFAIL  :  Data received /dev/inputX
> ---------------------------------------------------------------------
>
> After investigation, the single EV_SYN event can be processed on an
> old kernel.  However, the EV_SYN event handling has been modfied by
> the following patch:
> '4369c64c79a2("Input: Send events one packet at a time")'
>
> The patch is designed to reduce the time taken for processing a lot of
> events.  As a side effect, the single EV_SYN event handling depends on
> one or more other events(e.g. EV_REL), so it should be processed
> together with others, since this action is atomic.
>
> Only when the number of queued events(include EV_SYN) is greater than
> one can these events be processed.
> Please see the kenrel code in drivers/input/input.c, as below:
> --------------------------------------------------------------------
> static void input_handle_event(struct input_dev *dev,
> ...
>     if (disposition & INPUT_FLUSH) {
>             // num_vals: number of values queued in the current frame
>             if (dev->num_vals >= 2)
>                     input_pass_values(dev, dev->vals, dev->num_vals);
>                     dev->num_vals = 0;
> ...
> --------------------------------------------------------------------
>
> For example, steps to send an empty move and EV_SYN:
> -----------------------------------------------------
> send_event(fd, EV_REL, REL_X, 0);
> send_event(fd, EV_SYN, 0, 0);
> -----------------------------------------------------
>
> On an old kernel(before v3.7.0), the EV_SYN/SYN_REPORT event can be
> processed independently, so it is passed into /dev/input/eventX.
>
> On a new kernel(since v3.7.0), the EV_SYN/SYN_REPORT event depends on
> EV_REL/REL_X which is an empty move, so it is ignored.
>
> We feel this failure is due to the different mechanism of processing
> EV_SYN instead of a kernel bug, so we update no_events_queued() to
> fix it.
>
> Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> ---
>  testcases/kernel/input/input02.c      |  2 +-
>  testcases/kernel/input/input04.c      |  2 +-
>  testcases/kernel/input/input05.c      |  2 +-
>  testcases/kernel/input/input_helper.c | 26 +++++++++++++++++++++-----
>  testcases/kernel/input/input_helper.h |  2 +-
>  5 files changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/testcases/kernel/input/input02.c b/testcases/kernel/input/input02.c
> index df3b257..4f77758 100644
> --- a/testcases/kernel/input/input02.c
> +++ b/testcases/kernel/input/input02.c
> @@ -61,7 +61,7 @@ int main(int ac, char **av)
>  		case -1:
>  			tst_brkm(TBROK | TERRNO, cleanup, "fork() failed");
>  		default:
> -			if (no_events_queued(fd2))
> +			if (no_events_queued(fd2, 1))
>  				tst_resm(TPASS, "No data received in eventX");
>  			else
>  				tst_resm(TFAIL, "Data received in eventX");
> diff --git a/testcases/kernel/input/input04.c b/testcases/kernel/input/input04.c
> index 4b16ca7..e20b4f6 100644
> --- a/testcases/kernel/input/input04.c
> +++ b/testcases/kernel/input/input04.c
> @@ -57,7 +57,7 @@ int main(int ac, char **av)
>  		case -1:
>  			tst_brkm(TBROK | TERRNO, cleanup, "fork() failed");
>  		default:
> -			if (no_events_queued(fd2))
> +			if (no_events_queued(fd2, 0))
>  				tst_resm(TPASS,
>  					"No data received in /dev/inputX");
>  			else
> diff --git a/testcases/kernel/input/input05.c b/testcases/kernel/input/input05.c
> index 5ca01d8..e8251a3 100644
> --- a/testcases/kernel/input/input05.c
> +++ b/testcases/kernel/input/input05.c
> @@ -63,7 +63,7 @@ int main(int ac, char **av)
>  		case -1:
>  			tst_brkm(TBROK | TERRNO, cleanup, "fork() failed");
>  		default:
> -			if (no_events_queued(fd2))
> +			if (no_events_queued(fd2, 0))
>  				tst_resm(TPASS, "No data received in eventX");
>  			else
>  				tst_resm(TFAIL, "Data received in eventX");
> diff --git a/testcases/kernel/input/input_helper.c b/testcases/kernel/input/input_helper.c
> index 08fa81c..68b8b5f 100644
> --- a/testcases/kernel/input/input_helper.c
> +++ b/testcases/kernel/input/input_helper.c
> @@ -229,7 +229,15 @@ void destroy_device(int fd)
>  		unload_uinput();
>  }
>  
> -int no_events_queued(int fd)
> +/*
> + * the value of no_syn_evs_strict:
> + * 1: check that nothing is received in /dev/input/eventX
> + * 0: check that nothing or a EV_SYN/SYN_REPORT event is
> + *    received in /dev/input/eventX
> + * On an old kernel(before v3.7.0), a EV_SYN/SYN_REPORT event
> + * is always received even though we send empty events
> + */
> +int no_events_queued(int fd, int no_syn_evs_strict)
>  {
>  	struct pollfd fds = {.fd = fd, .events = POLLIN};
>  	int ret, res;
> @@ -241,13 +249,21 @@ int no_events_queued(int fd)
>  		res = read(fd, &ev, sizeof(ev));
>  
>  		if (res == sizeof(ev)) {
> -			tst_resm(TINFO,
> -			         "Unexpected ev type=%i code=%i value=%i",
> -			         ev.type, ev.code, ev.value);
> +			if (no_syn_evs_strict) {
> +				tst_resm(TINFO, "Unexpected ev type=%i code=%i "
> +					"value=%i", ev.type, ev.code, ev.value);
> +				return 0;
> +			}
> +
> +			if (!no_syn_evs_strict && ev.type != EV_SYN) {
> +				tst_resm(TINFO, "Unexpected event type %i "
> +					"expected %i", ev.type, EV_SYN);
> +				return 0;
> +			}
>  		}
>  	}
>  
> -	return ret == 0;
> +	return 1;
>  }
>  
>  static int check_device(void)
> diff --git a/testcases/kernel/input/input_helper.h b/testcases/kernel/input/input_helper.h
> index 9b85dc9..95c20f2 100644
> --- a/testcases/kernel/input/input_helper.h
> +++ b/testcases/kernel/input/input_helper.h
> @@ -29,6 +29,6 @@ int open_uinput(void);
>  void create_device(int fd);
>  void setup_mouse_events(int fd);
>  void destroy_device(int fd);
> -int no_events_queued(int fd);
> +int no_events_queued(int fd, int no_syn_evs_strict);
>  
>  #endif /* INPUT_HELPER_H */