[U-Boot] [PATCH 3/8] usb_kdb: only process events succesfully received

[Michal Suchánek]

On Tue, 2 Jul 2019 20:38:27 +0200
Marek Vasut <marex at denx.de> wrote:

> On 7/2/19 7:50 PM, Michal Suchánek wrote:
> > On Tue, 2 Jul 2019 18:58:54 +0200
> > Marek Vasut <marex at denx.de> wrote:
> >   
> >> On 7/2/19 4:22 PM, Michal Suchánek wrote:  
> >>> On Tue, 2 Jul 2019 15:11:07 +0200
> >>> Marek Vasut <marex at denx.de> wrote:
> >>>     
> >>>> On 7/2/19 3:04 PM, Michal Suchánek wrote:    
> >>>>> On Tue, 2 Jul 2019 13:58:30 +0200
> >>>>> Marek Vasut <marex at denx.de> wrote:
> >>>>>       
> >>>>>> On 7/1/19 5:56 PM, Michal Suchanek wrote:      
> >>>>>>> Causes unbound key repeat on error otherwise.
> >>>>>>>
> >>>>>>> Signed-off-by: Michal Suchanek <msuchanek at suse.de>
> >>>>>>> ---
> >>>>>>>  common/usb_kbd.c | 7 +++----
> >>>>>>>  1 file changed, 3 insertions(+), 4 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/common/usb_kbd.c b/common/usb_kbd.c
> >>>>>>> index cc99c6be0720..948f9fd68490 100644
> >>>>>>> --- a/common/usb_kbd.c
> >>>>>>> +++ b/common/usb_kbd.c
> >>>>>>> @@ -339,10 +339,9 @@ static inline void usb_kbd_poll_for_event(struct usb_device *dev)
> >>>>>>>  	struct usb_kbd_pdata *data = dev->privptr;
> >>>>>>>  
> >>>>>>>  	/* Submit a interrupt transfer request */
> >>>>>>> -	usb_submit_int_msg(dev, data->intpipe, &data->new[0], data->intpktsize,
> >>>>>>> -			   data->intinterval);
> >>>>>>> -
> >>>>>>> -	usb_kbd_irq_worker(dev);
> >>>>>>> +	if (!usb_submit_int_msg(dev, data->intpipe, &data->new[0],        
> >>>>>>
> >>>>>> Shouldn't you propagate return value from this function ? It can return
> >>>>>> ENOTSUPP.
> >>>>>>      
> >>>>>
> >>>>> If it did then probing keyboard would fail and we would not get here.      
> >>>>
> >>>> So there is no chance this function could return an error here, ever ?
> >>>> E.g. what if it's implemented and someone yanks the keyboard cable out
> >>>> just at the right time ?    
> >>>
> >>> It returns errors all the time with dwc2. That's why we need to check
> >>> for the error condition. We should not get here if probing the keyboard
> >>> failed, though. So if the function is not supported we will not get
> >>> here. Anyway, if it's not supported or the keyboard is missing it by
> >>> definition cannot provide useful result so we should not process it.    
> >>
> >> Except you start ignoring the error value from e.g. malfunctioning
> >> keyboard here, instead of propagating it, correct ?  
> > 
> > It was never propagated to start with. The return value was not checked
> > at all. What I do here is check the return value and not process the
> > data on error whatever it contains (like the keypress returned last
> > time valid data was received).  
> 
> I can see a patch which checks usb_kbd_poll_for_event() return value.
> Can you add one ?

What for? Apparently the keypress is processed in usb_kbd_irq_worker.
So checking the return value is needed to decide if the worker should
run, and is not particularly useful outside usb_kbd_poll_for_event. We
could signal a getc() failure but do we have any code handling getc()
failures?

Thanks

Michal