| Message ID | 20210307222240.380583-1-paul@crapouillou.net |
|---|---|
| State | Accepted |
| Commit | 02e699e33c13227c59253e0bc28aea6f6ee357ae |
| Headers | show |
| Series | [v3,1/3] input: gpio-keys: Remove extra call to input_sync | expand |
On Sun, Mar 07, 2021 at 10:22:38PM +0000, Paul Cercueil wrote: > The input_sync() function is already called after the loop in > gpio_keys_report_state(), so it does not need to be called after each > iteration within gpio_keys_gpio_report_event(). > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> Applied, thank you. -- Dmitry
On Sun, Mar 07, 2021 at 10:22:40PM +0000, Paul Cercueil wrote: > We want to be able to report the input event as soon as the debounce > delay elapsed. However, the current code does not really ensure that, > as it uses the jiffies-based schedule_delayed_work() API. With a small > enough HZ value (HZ <= 100), this results in some input events being > lost, when a key is quickly pressed then released (on a human's time > scale). > > Switching to hrtimers fixes this issue, and will work even on extremely > low HZ values (tested at HZ=24). This is however only possible if > reading the GPIO is possible without sleeping. If this condition is not > met, the previous approach of using a jiffies-based timer is taken. > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> Applied with minor edits to make more use of debounce_use_hrtimer flag. Thanks. -- Dmitry
Hi, * Dmitry Torokhov <dmitry.torokhov@gmail.com> [700101 02:00]: > On Sun, Mar 07, 2021 at 10:22:40PM +0000, Paul Cercueil wrote: > > We want to be able to report the input event as soon as the debounce > > delay elapsed. However, the current code does not really ensure that, > > as it uses the jiffies-based schedule_delayed_work() API. With a small > > enough HZ value (HZ <= 100), this results in some input events being > > lost, when a key is quickly pressed then released (on a human's time > > scale). > > > > Switching to hrtimers fixes this issue, and will work even on extremely > > low HZ values (tested at HZ=24). This is however only possible if > > reading the GPIO is possible without sleeping. If this condition is not > > met, the previous approach of using a jiffies-based timer is taken. > > > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > > Applied with minor edits to make more use of debounce_use_hrtimer flag. While testing Linux next I noticed that this patch causes a null pointer dereference at least when unbinding a gpio-keys instance, see below. Regards, Tony 8< ----------------- Unable to handle kernel NULL pointer dereference at virtual address 0000000c ... PC is at hrtimer_active+0xc/0x98 LR is at hrtimer_try_to_cancel+0x24/0x140 ... [<c01c43b8>] (hrtimer_active) from [<c01c50f4>] (hrtimer_try_to_cancel+0x24/0x140) [<c01c50f4>] (hrtimer_try_to_cancel) from [<c01c5224>] (hrtimer_cancel+0x14/0x4c) [<c01c5224>] (hrtimer_cancel) from [<bf1cae24>] (gpio_keys_attr_store_helper+0x1b8/0x1d8 [gpio_keys]) [<bf1cae24>] (gpio_keys_attr_store_helper [gpio_keys]) from [<bf1cae80>] (gpio_keys_store_disabled_keys+0x18/0x24 [gpio_keys]) [<bf1cae80>] (gpio_keys_store_disabled_keys [gpio_keys]) from [<c038ec7c>] (kernfs_fop_write_iter+0x10c/0x1cc) [<c038ec7c>] (kernfs_fop_write_iter) from [<c02df858>] (vfs_write+0x2ac/0x404) [<c02df858>] (vfs_write) from [<c02dfaf4>] (ksys_write+0x64/0xdc) [<c02dfaf4>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x58)
On Tue, Apr 06, 2021 at 11:37:07AM +0300, Tony Lindgren wrote: > Hi, > > * Dmitry Torokhov <dmitry.torokhov@gmail.com> [700101 02:00]: > > On Sun, Mar 07, 2021 at 10:22:40PM +0000, Paul Cercueil wrote: > > > We want to be able to report the input event as soon as the debounce > > > delay elapsed. However, the current code does not really ensure that, > > > as it uses the jiffies-based schedule_delayed_work() API. With a small > > > enough HZ value (HZ <= 100), this results in some input events being > > > lost, when a key is quickly pressed then released (on a human's time > > > scale). > > > > > > Switching to hrtimers fixes this issue, and will work even on extremely > > > low HZ values (tested at HZ=24). This is however only possible if > > > reading the GPIO is possible without sleeping. If this condition is not > > > met, the previous approach of using a jiffies-based timer is taken. > > > > > > Signed-off-by: Paul Cercueil <paul@crapouillou.net> > > > > Applied with minor edits to make more use of debounce_use_hrtimer flag. > > While testing Linux next I noticed that this patch causes a null pointer > dereference at least when unbinding a gpio-keys instance, see below. Ugh, my "minor edits" did screw things up ;( as I mixed up release and debounce timers. I'll fix it up. > > Regards, > > Tony > > 8< ----------------- > Unable to handle kernel NULL pointer dereference at virtual address 0000000c > ... > PC is at hrtimer_active+0xc/0x98 > LR is at hrtimer_try_to_cancel+0x24/0x140 > ... > [<c01c43b8>] (hrtimer_active) from [<c01c50f4>] (hrtimer_try_to_cancel+0x24/0x140) > [<c01c50f4>] (hrtimer_try_to_cancel) from [<c01c5224>] (hrtimer_cancel+0x14/0x4c) > [<c01c5224>] (hrtimer_cancel) from [<bf1cae24>] (gpio_keys_attr_store_helper+0x1b8/0x1d8 [gpio_keys]) > [<bf1cae24>] (gpio_keys_attr_store_helper [gpio_keys]) from [<bf1cae80>] (gpio_keys_store_disabled_keys+0x18/0x24 [gpio_keys]) > [<bf1cae80>] (gpio_keys_store_disabled_keys [gpio_keys]) from [<c038ec7c>] (kernfs_fop_write_iter+0x10c/0x1cc) > [<c038ec7c>] (kernfs_fop_write_iter) from [<c02df858>] (vfs_write+0x2ac/0x404) > [<c02df858>] (vfs_write) from [<c02dfaf4>] (ksys_write+0x64/0xdc) > [<c02dfaf4>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x58) > -- Dmitry
diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c index 77bac4ddf324..7fcb2c35c5cc 100644 --- a/drivers/input/keyboard/gpio_keys.c +++ b/drivers/input/keyboard/gpio_keys.c @@ -373,7 +373,6 @@ static void gpio_keys_gpio_report_event(struct gpio_button_data *bdata) } else { input_event(input, type, *bdata->code, state); } - input_sync(input); } static void gpio_keys_gpio_work_func(struct work_struct *work) @@ -382,6 +381,7 @@ static void gpio_keys_gpio_work_func(struct work_struct *work) container_of(work, struct gpio_button_data, work.work); gpio_keys_gpio_report_event(bdata); + input_sync(bdata->input); if (bdata->button->wakeup) pm_relax(bdata->input->dev.parent);
The input_sync() function is already called after the loop in gpio_keys_report_state(), so it does not need to be called after each iteration within gpio_keys_gpio_report_event(). Signed-off-by: Paul Cercueil <paul@crapouillou.net> --- Notes: v2: Keep the input_sync() within gpio_keys_report_state() so that it's not called at every iteration of the loop. v3: No change drivers/input/keyboard/gpio_keys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)