On Wed, 2006-05-17 at 21:46 -0700, [email protected] 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 ;)
Arjan van de Ven wrote:
> On Wed, 2006-05-17 at 21:46 -0700, [email protected] 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 ;)
Couldn't find any info on that one, are you sure you spelled it correctly?
>
>>+
>>+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?
>
Well, I don't know. When should EXPORT_SYMBOLs be EXPORT_SYMBOL_GPLs?
>
>>+
>>+#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?
Well, it's never changed, locked or not. But maybe we can get rid of
this condlocking alltogether, see my reply for Andrew Morton.
>
>>+ if (!events) {
>>+ debug("no actions");
>>+ del_timer(&ff->timer);
>
>
> are you really sure you don't need del_timer_sync() here?
>
Yes, this function is also called from inside the timer in question and
del_timer_sync() would block.
>
>
>>+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?
>
I count 76 bytes (x86), is that too much?
>>+ } else {
>>+ ret = -ENOSYS;
>
>
> that is almost always a wrong return value
>
It's returned when the device is mem-capable but driver doesn't
implement set_gain() but sets FF_GAIN or when driver doesn't implement
set_autocenter() but sets FF_AUTOCENTER. But yes, if that happens, it's
a driver bug, so maybe this is not correct use for -ENOSYS. Probably
there should be BUG() too here.
>>+ 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 ;)
Well, I'm not. Is there an alternative?
--
Anssi Hannula
On Mon, 2006-05-22 at 19:12 +0300, Anssi Hannula wrote:
> Arjan van de Ven wrote:
> > On Wed, 2006-05-17 at 21:46 -0700, [email protected] 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 ;)
>
> Couldn't find any info on that one, are you sure you spelled it correctly?
>
> >
#ifdef DEBUG
#define pr_debug(fmt,arg...) \
printk(KERN_DEBUG fmt,##arg)
#else
#define pr_debug(fmt,arg...) \
do { } while (0)
#endif
in linux/kernel.h
> Well, I don't know. When should EXPORT_SYMBOLs be EXPORT_SYMBOL_GPLs?
>
if it's linux-only code or otherwise very internal, _GPL is usually the
right thing
> > hmmm stack space?
> >
>
> I count 76 bytes (x86), is that too much?
it's sort of ok, just make sure it doesn't grow more
> >
> > that is almost always a wrong return value
> >
>
> It's returned when the device is mem-capable but driver doesn't
> implement set_gain() but sets FF_GAIN or when driver doesn't implement
> set_autocenter() but sets FF_AUTOCENTER. But yes, if that happens, it's
> a driver bug, so maybe this is not correct use for -ENOSYS. Probably
> there should be BUG() too here.
-EINVAL or so would be better; -ENOSYS basically is "not implemented
system call", which is totally off topic in this context
>
> >>+ 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 ;)
>
> Well, I'm not. Is there an alternative?
__set_bit() is not atomic, and thus a lot faster if you don't need
atomic behavior..