Re: [Nouveau] [PATCH] drm/nouveau/kms: Implement KDB debug hooks for nouveau KMS.

[Maxim Levitsky <maximlevitsky@gmail.com>]

On Wed, 2010-09-22 at 19:07 +0200, Maxim Levitsky wrote:
> On Wed, 2010-09-22 at 16:06 +0200, Maxim Levitsky wrote: 
> > On Wed, 2010-09-22 at 16:03 +0200, Maxim Levitsky wrote: 
> > > On Wed, 2010-09-22 at 03:42 +0200, Maxim Levitsky wrote: 
> > > > On Thu, 2010-09-02 at 13:46 +0300, Maxim Levitsky wrote: 
> > > > > On Wed, 2010-09-01 at 06:35 -0500, Jason Wessel wrote: 
> > > > > > On 09/01/2010 04:56 AM, Maxim Levitsky wrote:
> > > > > > > On Thu, 2010-08-19 at 13:55 -0400, Chris Ball wrote: 
> > > > > > >   
> > > > > > >> Hi,
> > > > > > >>
> > > > > > >> Here's a patch to add support for KMS debugging to Nouveau, along the
> > > > > > >> style of the previous patches for Intel¹ and Radeon².  I'm only able
> > > > > > >> to test on nv50 here, so a test on nv04 would be much appreciated,
> > > > > > >> and I've published instructions on how to test here³.  Thanks!
> > > > > > >>
> > > > > > >> - Chris.
> > > > > > >>     
> > > > > > >
> > > > > > > Hi,
> > > > > > >
> > > > > > > I just tried that patch, but unfortunately nether with nor without it
> > > > > > > kdb seems not to work.
> > > > > > > It could be id10t error from my side, but I did test the kdb in the past
> > > > > > > with few KMS patches, and it seemed to work.
> > > > > > >
> > > > > > > Now I can't even get its prompt on the console.
> > > > > > >
> > > > > > > This is what I do:
> > > > > > >
> > > > > > > echo kbd | sudo tee /sys/module/kgdboc/parameters/kgdboc
> > > > > > > (also tried booting with kgdboc=kbd)
> > > > > > >   
> > > > > > 
> > > > > > Try changing it to kgdboc=kms,kbd  or the "echo kms,kbd"
> > > > > > 
> > > > > > When you use only the kbd, the kms feature is not activated.
> > > > > This doesn't help.
> > > > > 
> > > > > I am afraid that this bug isn't related to kms, but rather is generic.
> > > > 
> > > > I turns out that it was the NMI watchdog that I had enabled.
> > > > Without it kdb works very well, including the kms support.
> > > Please disregard this. kdb works with nmi watchdog now as well.
> > > Probably something was fixed, maybe unrelated to it.
> > > 
> > > > 
> > > > It would be better if you were to detect kms instead of adding an
> > > > explicit param to kgdboc cmd line.
> > > > 
> > > > Also found out that after a debug session with Alt+SysRQ+g and X
> > > > running, these keys aren't released. I had to press on all of them to
> > > > make them release.
> > > > It makes sense as kgdboc in that case reads directly from keyboard port.
> > > And I see that kgdb actually has a code that works that around.
> > > I suspect that what happens is that keys are released before X continues
> > > running, and therefore it doesn't pick these events up.
> > 
> > However an evtest on input event running on kernel tty, still only picks
> > release of the alt key.
> 
> [Dropped nouveau list, because this is offtopic there]
> 
> I pretty much got to the bottom of this.
> There are 2 separate issues:
> 
> 
> 1. SysRq handler is now a input 'filter', which means that it can 'eat'
> input events, so they don't show up on input bus.
> It does so while sysrq key is down.
> So sysrq and 'g' events never reach the kernel kbd driver and therefore
> the hack to release them doesn't work.
> 
> 2. The kbd_clear_keys_helper injects the keyup events alright, but it
> doesn't inject SYN events, and therefore X evdev driver doesn't pick
> these injected events untill next SYN event. 
> 
> This patch makes key release work in expense of showing sysrq key to userspace, which isn't that good,
> because now Alt+SysRQ causes a screen capture by default.
> In my opinion the sysrq filter should stay.
> We should just make kdb hook into atkbd and do the key release there.
> This should both result in cleaner/more robust code, and make this issue disappear.
> I'll look at doing that.
> 
> 
> diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
> index 0c6c641..7df6af5 100644
> --- a/drivers/char/keyboard.c
> +++ b/drivers/char/keyboard.c
> @@ -368,6 +368,7 @@ static int kbd_clear_keys_helper(struct input_handle *handle, void *data)
>  {
>  	unsigned int *keycode = data;
>  	input_inject_event(handle, EV_KEY, *keycode, 0);
> +	input_inject_event(handle, EV_SYN, SYN_REPORT, 0);
>  	return 0;
>  }
>  
> diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
> index ef31bb8..db1eb12 100644
> --- a/drivers/char/sysrq.c
> +++ b/drivers/char/sysrq.c
> @@ -601,7 +601,7 @@ static bool sysrq_filter(struct input_handle *handle, unsigned int type,
>  	}
>  
>  out:
> -	return sysrq_down;
> +	return 0;
>  }
>  
>  static int sysrq_connect(struct input_handler *handler,
> 
> 
> Best regards,
> 	Maxim Levitsky
> 
Ping.

Maxim Levitsky


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