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SubjectRe: [PATCH] input: spi: Driver for SPI data stream driven vibrator
On Tue, Oct 26, 2010 at 06:50:33PM +0200, ilkka.koskinen@nokia.com wrote:
> Hi Grant and thanks for comments,
[...]
> >> +static int vibra_spi_playback(struct input_dev *input, int effect_id,
> >int value)
> >> +{
> >> + struct vibra_data *vibra = input_get_drvdata(input);
> >> + struct effect_info *einfo = &vibra->effects[effect_id];
> >> + struct ff_effect *ff_effect = &input->ff->effects[effect_id];
> >> +
> >> + if (!vibra->workqueue)
> >> + return -ENODEV;
> >> +
> >> + if (test_bit(FF_EFFECT_UPLOADING, &einfo->flags))
> >> + return -EBUSY;
> >> +
> >> + if (value == 0) {
> >> + /* Abort the given effect */
> >> + if (test_bit(FF_EFFECT_PLAYING, &einfo->flags))
> >> + __set_bit(FF_EFFECT_ABORTING, &einfo->flags);
> >> +
> >> + __clear_bit(FF_EFFECT_QUEUED, &einfo->flags);
> >> + } else {
> >> + /* Move the given effect as the next one */
> >> + __clear_bit(FF_EFFECT_QUEUED,
> >> + &vibra->effects[vibra->next_effect].flags);
> >> +
> >> + vibra->next_effect = effect_id;
> >> + __set_bit(FF_EFFECT_QUEUED, &einfo->flags);
> >> + __clear_bit(FF_EFFECT_ABORTING, &einfo->flags);
> >> + einfo->stop_at = jiffies +
> >> + msecs_to_jiffies(ff_effect->replay.length);
> >> +
> >> + if (vibra->status == IDLE) {
> >> + vibra->status = STARTED;
> >> + queue_work(vibra->workqueue, &vibra->play_work);
> >> + }
> >> + }
> >
> >I can't speak anything about the input event handling because I'm not
> >very familiar with it. However, it looks like the shared effect data
> >(vibra->effects) is getting modified outside of a critical region. Is
> >this safe?

Hmmm, I don't know why the force feedback layer is using a spin lock,
but it looks like overkill. Since you're already deferring work, I
would look at queueing the request and pushing down the spin lock
exposure as much as possible, but I'm really not the expert on the
input layer.



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