Messages in this thread | | | Date | Mon, 17 Aug 2009 11:00:23 +0300 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH 1/1] VIDEO: console, use DIV_ROUND_UP |
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On (08/17/09 09:48), Jiri Slaby wrote: > On 08/17/2009 09:31 AM, Sergey Senozhatsky wrote: > > On (08/17/09 09:15), Jiri Slaby wrote: > >> Not at all. I was writing about about (X + 7) / 8 [or >> 3] which is > >> DIV_ROUND_UP(X, 8). > >> > > As far as I can understand: > > DIV_ROUND_UP(61, 8): > > (111101 + 111) >> 3 -> 1000 == 8 > > > > (int)(61/8) == 7 > > Yeah, that's why there is the ROUND_UP keyword in the macro. > > I mean this: > -- > Use DIV_ROUND_UP explicitly instead of manual shifts and adds. It makes > the code more readable and consistent (sometimes there were shifts, > sometimes divs). > > There is no change on the assembly level (compilers should do the right > job). > > Signed-off-by: Jiri Slaby <jirislaby@gmail.com> > --- > drivers/video/console/bitblit.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/video/console/bitblit.c b/drivers/video/console/bitblit.c > index 69864b1..6b7c8fb 100644 > --- a/drivers/video/console/bitblit.c > +++ b/drivers/video/console/bitblit.c > @@ -25,7 +25,7 @@ static inline void update_attr(u8 *dst, u8 *src, int attribute, > struct vc_data *vc) > { > int i, offset = (vc->vc_font.height < 10) ? 1 : 2; > - int width = (vc->vc_font.width + 7) >> 3; > + int width = DIV_ROUND_UP(vc->vc_font.width, 8);
So... In general, ((vc->vc_font.width + 7) >> 3) == DIV_ROUND_UP(vc->vc_font.width, 8) - 1; That means: unsigned int cellsize = vc->vc_font.height * width; now is unsigned int cellsize = vc->vc_font.height * (width + 1);
Are you sure we really can use DIV_ROUND_UP?
Sergey
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