Subject: Re: [PATCH V2 2/2] drivers: input: keyboard

From: Dmitry Torokhov <[email-masked]>
Date: Thu, 9 Jan 2020 17:20:13 -0800

On Wed, Jan 08, 2020 at 01:26:09PM +0200, Andy Shevchenko wrote:
> On Wed, Jan 08, 2020 at 04:46:02PM +0800, Yingjoe Chen wrote:
> > On Wed, 2020-01-08 at 14:29 +0800, fengping yu wrote:
> 
> > > +	tasklet_init(&keypad->tasklet, kpd_keymap_handler,
> > > +		     (unsigned long)keypad);
> > > +
> > > +	writew((u16)(keypad->key_debounce & KPD_DEBOUNCE_MASK),
> > > +		     keypad->base + KP_DEBOUNCE);
> > 
> > You use a 13 bits mask and set it directly to KP_DEBOUNCE register. Are
> > you sure the debounce unit is ms?
> > 
> > > +
> > > +	/* register IRQ */
> > > +	err = request_irq(keypad->irqnr, kpd_irq_handler, IRQF_TRIGGER_NONE,
> > > +			  KPD_NAME, keypad);
> > 
> > please consider using devm_request_irq, otherwise you have to free it in
> > _remove function.
> 
> No, you may not use devm_*_irq() when tasklets are in use. There is a nasty
> race condition.
> 
> Actually the rule of thumb is to NOT use devm_*_irq() unless you exactly know
> what you are doing.
> 
> P.S. Why simple not to switch to threaded IRQ handler and drop tasklet? In such
> case devm_*_irq() is fine.

Actually, we are simply reading iomem data and forward it to input
subsystem, there is no need to use threaded interrupt nor the tasklet.

Thanks.

-- 
Dmitry

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