Re: [PATCH/RFC v10 08/19] leds: Add support for max77693 mfd flash cell
From: Pavel Machek <hidden>
Date: 2015-01-12 13:25:28
Also in:
linux-leds, linux-media, lkml
From: Pavel Machek <hidden>
Date: 2015-01-12 13:25:28
Also in:
linux-leds, linux-media, lkml
Hi!
quoted
quoted
+struct max77693_sub_led { + /* related FLED output identifier */->flash LED, about 4x.quoted
+/* split composite current @i into two @iout according to @imax weights */ +static void __max77693_calc_iout(u32 iout[2], u32 i, u32 imax[2]) +{ + u64 t = i; + + t *= imax[1]; + do_div(t, imax[0] + imax[1]); + + iout[1] = (u32)t / FLASH_IOUT_STEP * FLASH_IOUT_STEP; + iout[0] = i - iout[1]; +}Is 64-bit arithmetics neccessary here? Could we do the FLASH_IOUT_STEP divisons before t *=, so that 64-bit division is not neccessary?It is required. All these operations allow for splitting the composite current into both outputs according to weights given in the imax array.
I know.
What about this?
static void __max77693_calc_iout(u32 iout[2], u32 i, u32 imax[2])
{
u32 t = i;
t *= imax[1] / FLASH_IOUT_STEP;
t = t / (imax[0] + imax[1]);
t /= FLASH_IOUT_STEP
iout[1] = (u32)t;
iout[0] = i - iout[1];
}
Does it lack precision?
Thanks,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html