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    SubjectRe: [PATCH try #3] Input/Joystick Driver: add support AD7142 joystick driver
    On 10/15/07, Dmitry Torokhov <dmitry.torokhov@gmail.com> wrote:
    > Hi Bryan,
    >
    > On 10/15/07, Bryan Wu <bryan.wu@analog.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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