Hello Sean, On Fri, Dec 04, 2020 at 11:40:36AM +0000, Sean Young wrote: > On Fri, Dec 04, 2020 at 12:21:15PM +0100, Uwe Kleine-König wrote: > > On Fri, Dec 04, 2020 at 12:42:15AM +0100, Lino Sanfilippo wrote: > > > On 29.11.20 at 19:10, Uwe Kleine-König wrote: > > > > You're storing an unsigned long long (i.e. 64 bits) in an u32. If > > > > you are sure that this won't discard relevant bits, please explain > > > > this in a comment for the cursory reader. > > > > > > What about an extra check then to make sure that the period has not been > > > truncated, > > > e.g: > > > > > > value = DIV_ROUND_CLOSEST_ULL(state->period, scaler); > > > > > > /* dont accept a period that is too small or has been truncated */ > > > if ((value < PERIOD_MIN) || > > > (value != DIV_ROUND_CLOSEST_ULL(state->period, scaler))) > > > return -EINVAL; > > > > I'd make value an unsigned long long and check for > 0xffffffff instead > > of repeating the (expensive) division. (Hmm, maybe the compiler is smart > > enough to not actually repeat it, but still.) > > I wonder where you got that idea from.
I don't know how to honestly answer your question. Which idea do you mean? That divisions are expensive? Or that compilers might be smart? And do you consider it a good idea? Or do you disagree? Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |
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