Messages in this thread | | | Date | Tue, 2 Nov 2021 16:51:40 -0700 | From | "dmitry.torokhov" <> | Subject | Re: [PATCH v9] tty: Fix the keyboard led light display problem |
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On Tue, Nov 02, 2021 at 03:09:20PM +0800, 常廉志 wrote: > > > > > > Hi Dmitry, I don’t know if I fully understand what you mean, but I will > > > try to fully explain the intent of the current patch. > > > (1) What is the current bug phenomenon? I will describe with the Num > > > Lock indicator as the object here. > > > > > > Phenomenon 1: Suppose that Xorg is bound to tty1 in the desktop environment. > > > At this time, the Num light of the keyboard is on, and the keypad can input numbers > > > normally; assume that the state of the keyboard light saved by tty2 itself is the > > > opposite (the Num light is off, The keypad cannot enter numbers); at this time, > > > if we use the key combination "ctrl+alt+F2" to switch the system to tty2, we will find > > > that the Num light is still on, but the keypad cannot enter numbers. > > > > > > Phenomenon 2: Assuming that you are currently in the tty2 environment, the Num > > > light of the keyboard is on, and the keypad can input numbers normally; assume that > > > the Num state saved by Xorg is the same as that of tty2 (the Num light is on, and the > > > keypad can input numbers normally); At this point, if we use the key combination > > > "ctrl+alt+F1" to switch the system to tty1 (that is, to switch to the desktop environment) > > > , we will find that the Num light will not light up, but the small keyboard can input numbers . > > > > > > (2) Why do these two phenomena occur? > > > The variable static unsigned int ledstate is defined in keyboard.c. ledstate should be used to > > > tell VT the current state of the keyboard light, because after each VT sets the state of the > > > keyboard light, it will synchronize the latest keyboard light state to ledstate( (Implemented > > > in the kbd_bh() function). > > > > > > Then the problem comes. The scope of ledstate is only in VT, and it cannot include all the > > > scenes where the keyboard light is set. And, in the desktop environment, "kb->kbdmode == > > > VC_OFF" of tty1, at this time, through the NumLock button, only Xorg's own state can be > > > changed, and the led state stored by tty1 cannot be changed (implemented in the kbd_keycode() > > > function), This results in that the kb->ledflagstate stored by tty1 itself and the ledstate in the tty > > > environment are always 0 at this time. > > > > > > When we switch tty, the VT code compares the current tty's kb->ledflagstate and ledstate values. > > > If they are inconsistent, change the state of the keyboard light (implemented in the kbd_bh() function). > > > > > > In phenomenon 1, in the desktop environment, although the actual state saved by xorg is 1, the state > > > of ledstate of tty is always 0. In the environment of tty2, the state of kb->ledflagstate of tty2 is also 0. > > > At this point, in the kbd_bh() function, comparing these two values is equal, there is no need to set the > > > led light state to the keyboard. So after switching to tty2, the Num light is still on, but the small > > > keyboard cannot input numbers. > > > > > > In phenomenon 2, in the tty2 environment, the state of ledstate is set to 1, but the kb->ledflagstate of > > > tty1 is 0. At this time, the two values are not equal in the kbd_bh() function, so set the led The light > > > status to the keyboard. Xorg did not redistribute the configuration during this process is also one of > > > the reasons. And even if Xorg re-issues the configuration at this time, it will cause confusion and only > > > one can be set. > > > > > > (3) How to solve it? > > > To solve the problem of phenomenon 1, we must first enable ledstate to correctly reflect the current > > > state of the keyboard light. Therefore, the solution to all versions of patch is to synchronize the > > > latest led state of the input device to ledstate. > > > You assume that input's device NumLock LED reflects the state of > > terminal. That does not have to be the case. > > > Now how to solve this... On VT switch redraw_screen() calls > > vt_set_leds_compute_shiftstate(). Can we do something like: > > > /* > > * On VT switch pretend our led state is opposite of target > > * state to ensure we refresh all leds. > > */ > > spin_lock_irqsave(&led_lock, flags); > > leds = getleds(); > > leds |= (unsigned int)kbd->lockstate << 8; > > ledstate = ~leds; > > spin_unlock_irqrestore(&led_lock, flags); > > > > set_leds(); > > > > ? > Hi Dmitry: > /* > * The following piece of code exists in the kbd_bh() function > */ > spin_lock_irqsave(&led_lock, flags); > leds = getleds(); > leds |= (unsigned int)kbd->lockstate << 8; > ledstate = ~leds;
^^^^^^^^^^^^^^^^^
This is not the exact code that exists in kbd_bh(). It lacks the line above which should cause LEDs be synchronized once set_leds()/kbd_bh() runs.
> spin_unlock_irqrestore(&led_lock, flags); > > Moreover, the process of calling the set_leds() function is > the process of calling the kbd_bh function: > static void set_leds(void) > { > tasklet_schedule(&keyboard_tasklet); > } > static DECLARE_TASKLET_DISABLED(keyboard_tasklet, kbd_bh); > > I don't really understand what you mean here, but one thing > can be confirmed, my patch just synchronizes the current input > device's led state to ledstate. Moreover, after VT's > kb->ledflagstate is set to the input device, it will also > be synchronized to ledstate (the original logic of the kbd_bh() > function), which does not destroy the original internal logic of > VT. In addition, I have tested it, whether it is switching > between the desktop environment (tty1) and tty2~6, or switching > between tty2~6, the indicator status of the keyboard light is > correct, and it is normal in the multi-keyboard state. .
And I keep telling you that your approach to solving the problem is not correct because state of a random input device is not necessarily connected to the state of a VT.
Thanks.
-- Dmitry
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