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

From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Yingjoe Chen <yingjoe.chen@mediatek.com>,
	fengping yu <fengping.yu@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
	Olof Johansson <olof@lixom.net>,
	Aisheng Dong <aisheng.dong@nxp.com>,
	Anson Huang <Anson.Huang@nxp.com>,
	Maxime Ripard <mripard@kernel.org>,
	Leonard Crestez <leonard.crestez@nxp.com>,
	Dinh Nguyen <dinguyen@kernel.org>,
	Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Arnd Bergmann <arnd@arndb.de>, Mark Brown <broonie@kernel.org>,
	Thierry Reding <treding@nvidia.com>,
	YueHaibing <yuehaibing@huawei.com>,
	Stefan Agner <stefan@agner.cn>, Jacky Bai <ping.bai@nxp.com>,
	Marco Felsch <m.felsch@pengutronix.de>,
	devicetree@vger.kernel.org, wsd_upstream@mediatek.com,
	linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
	linux-input@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH V2 2/2] drivers: input: keyboard
Date: Thu, 9 Jan 2020 17:20:13 -0800	[thread overview]
Message-ID: <20200110012013.GR8314@dtor-ws> (raw)
In-Reply-To: <20200108112609.GN32742@smile.fi.intel.com>

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