linux-kernel - Re: [PATCH try #3] Input/Joystick Driver: add support AD7142 joystick driver

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Message-ID: <386072610710151024s13e9c16qd7c974cde8000a9@mail.gmail.com>
Date:	Tue, 16 Oct 2007 01:24:28 +0800
From:	"Bryan Wu" <cooloney.lkml@...il.com>
To:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
Cc:	bryan.wu@...log.com, "Andrey Panin" <pazke@...pac.ru>,
	"Roel Kluin" <12o3l@...cali.nl>,
	"Ahmed S. Darwish" <darwish.07@...il.com>,
	linux-input@...ey.karlin.mff.cuni.cz,
	linux-joystick@...ey.karlin.mff.cuni.cz,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	"Jean Delvare" <khali@...ux-fr.org>
Subject: Re: [PATCH try #3] Input/Joystick Driver: add support AD7142 joystick driver

On 10/15/07, Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:
> Hi Bryan,
>
> On 10/15/07, Bryan Wu <bryan.wu@...log.com> wrote:
> > +
> > +static int ad7142_thread(void *nothing)
> > +{
> > +       do {
> > +               wait_for_completion(&ad7142_completion);
> > +               ad7142_decode();
> > +               enable_irq(CONFIG_BFIN_JOYSTICK_IRQ_PFX);
> > +       } while (!kthread_should_stop());
> > +
>
> No, this is not going to work well:
> - you at least need to reinitialize the completion before enabling
> IRQ, otherwise you will spin in a very tight loop
> - if noone would touch the joystick ad7142_clsoe would() block
> infinitely because noone would signal the completion and
> ad7142_thread() would never stop.
>
> Completion is just not a good abstraction here... Please use work
> abstraction and possibly a separate workqueue.

Yes, I agree with you now, although I have a little concern about the
possibility of big delay introduced by workqueue.

>
> > +
> > +       ad7142_task = kthread_run(ad7142_thread, NULL, "ad7142_task");
> > +       if (IS_ERR(ad7142_task)) {
> > +               printk(KERN_ERR "serio: Failed to start kseriod\n");
>
> kseriod?

My fault, I did't notice this copy words from other driver.

>
> > +               return PTR_ERR(ad7142_task);
> > +       }
> > +       return 0;
> > +}
> > +
> > +static void ad7142_close(struct input_dev *dev)
> > +{
>
> Don't you need to write something over i2c to tell the device to shut
> down? As it is now I expect the device to continue raising its IRQ
> until kernel decides that it is unhandled and should be ignored.
>
I am not sure here, should do some investigate of the hardware datasheet.


> > +       free_irq(CONFIG_BFIN_JOYSTICK_IRQ_PFX, ad7142_interrupt);
>
> Ok, so you freeing IRQ here, but it is allocated in ad7142_probe().
> What happen if you try to open device after it was closed?
>
Yes, it should be move to ad7142_detach_client()

> > +       kthread_stop(ad7142_task);
> > +}
> > +
> > +static int __init ad7142_init(void)
> > +{
> > +       return i2c_add_driver(&ad7142_driver);
> > +}
> > +
> > +static void __exit ad7142_exit(void)
> > +{
> > +       i2c_del_driver(&ad7142_driver);
> > +       input_unregister_device(ad7142_dev);
>
> input_unregister_device() should be in ad7142_detach_client? I am not
> sure i2c - there seems to be 2 interface styles and you probably need
> to use the new one. I am CC-inj Jean on this.
>
Yes, no need input_unregister_device() here.

Thanks a lot for you kindly review.
I will resend update patch later.

Best Regards,
-Bryan Wu
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