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

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Date:	Mon, 15 Oct 2007 11:48:17 -0400
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	bryan.wu@...log.com
Cc:	"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

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.

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

kseriod?

> +               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.

> +       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?

> +       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.

> +}
> +
> +module_init(ad7142_init);
> +module_exit(ad7142_exit);
> --
> 1.5.3.4
>


-- 
Dmitry
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