Re: + input-new-force-feedback-interface.patch added to -mm tree

[Arjan van de Ven <arjan@infradead.org>]

On Wed, 2006-05-17 at 21:46 -0700, akpm@osdl.org wrote:
> +
> +#ifdef DEBUG
> +#define debug(format, arg...) printk(KERN_DEBUG "ff-effects: " format "\n" , ## arg)
> +#else
> +#define debug(format, arg...) do {} while (0)
> +#endif

please just use the existing prdebug() thing for this, no need to invent
your own ;)

> +
> +EXPORT_SYMBOL(input_ff_allocate);
> +EXPORT_SYMBOL(input_ff_register);
> +EXPORT_SYMBOL(input_ff_upload);
> +EXPORT_SYMBOL(input_ff_erase);

should these be _GPL exports?


> +
> +#define spin_ff_cond_lock(_ff, _flags)					  \
> +	do {								  \
> +		if (!_ff->driver->playback)				  \
> +			spin_lock_irqsave(&_ff->atomiclock, _flags);	  \
> +	} while (0);
> +
> +#define spin_ff_cond_unlock(_ff, _flags)					  \
> +	do {								  \
> +		if (!_ff->driver->playback)				  \
> +			spin_unlock_irqrestore(&_ff->atomiclock, _flags); \
> +	} while (0);


hmmm conditional locking like this always makes me very nervous... what
is preventing ->playback from changing halfway a locked sequence?

> +	if (!events) {
> +		debug("no actions");
> +		del_timer(&ff->timer);

are you really sure you don't need del_timer_sync() here?



> +static void input_ff_timer(unsigned long timer_data)
> +{
> +	struct input_dev *dev = (struct input_dev *) timer_data;
> +	struct ff_device *ff = dev->ff;
> +	struct ff_effect effect;
> +	int i;
> +	unsigned long flags;
> +	int effects_pending;
> +	unsigned long effect_handled[NBITS(FF_EFFECTS_MAX)];


hmmm stack space?

> +		} else {
> +			ret = -ENOSYS;

that is almost always a wrong return value
> +	if (test_bit(FF_CONSTANT, dev->ff->flags))
> +		set_bit(FF_CONSTANT, dev->ffbit);
> +	if (test_bit(FF_SPRING, dev->ff->flags))
> +		set_bit(FF_SPRING, dev->ffbit);
> +	if (test_bit(FF_FRICTION, dev->ff->flags))
> +		set_bit(FF_FRICTION, dev->ffbit);
> +	if (test_bit(FF_DAMPER, dev->ff->flags))
> +		set_bit(FF_DAMPER, dev->ffbit);
> +	if (test_bit(FF_INERTIA, dev->ff->flags))

are you really sure you need atomic set_bit()'s here??
if so.. I think you have a race ;)