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SubjectRe: [PATCH] staging/hv/osd: don't reimplement ALIGN macro
On Wed, Jan 19, 2011 at 02:07:30PM +0100, Uwe Kleine-König wrote:
> Hello Jiri,
>
> On Wed, Jan 19, 2011 at 01:43:57PM +0100, Jiri Slaby wrote:
> > On 01/19/2011 09:54 AM, Uwe Kleine-König wrote:
> > > On Tue, Jan 18, 2011 at 09:37:15PM -0800, Greg KH wrote:
> > >> On Tue, Jan 18, 2011 at 04:39:11PM +0100, Uwe Kleine-König wrote:
> > >>> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> > >>> ---
> > >>> drivers/staging/hv/osd.h | 5 ++---
> > >>> 1 files changed, 2 insertions(+), 3 deletions(-)
> > >>>
> > >>> diff --git a/drivers/staging/hv/osd.h b/drivers/staging/hv/osd.h
> > >>> index ce064e8..61ae54c 100644
> > >>> --- a/drivers/staging/hv/osd.h
> > >>> +++ b/drivers/staging/hv/osd.h
> > >>> @@ -28,10 +28,9 @@
> > >>> #include <linux/workqueue.h>
> > >>>
> > >>> /* Defines */
> > >>> -#define ALIGN_UP(value, align) (((value) & (align-1)) ? \
> > >>> - (((value) + (align-1)) & ~(align-1)) : \
> > >>> - (value))
> > >>> +#define ALIGN_UP(value, align) ALIGN((value), (align))
> > >>
> > >> How about dropping ALIGN_UP entirely and just using the built-in ALIGN()
> > >> macro instead?
> > > Can do.
> > >
> > >>> #define ALIGN_DOWN(value, align) ((value) & ~(align-1))
> > >>
> > >> Any chance to get rid of this as well with the ALIGN() macro, or is that
> > >> really not possible?
> > > it would be
> > >
> > > #define ALIGN_DOWN(value, align) ALIGN((value) - (align) + 1, (align))
> > >
> > > I think, but as it's only used once it might be easier to just use ALIGN
> > > there, too.
> > >
> > > BTW, it's used as follows:
> > >
> > > #define NUM_PAGES_SPANNED(addr, len) ((ALIGN(addr+len, PAGE_SIZE) - \
> > > ALIGN_DOWN(addr, PAGE_SIZE)) >> \
> > > PAGE_SHIFT)
> >
> > (DIV_ROUND_UP(addr+len, PAGE_SIZE) - ((addr) >> PAGE_SHIFT)))
> >
> > or maybe better
> >
> > (PAGE_ALIGN(addr+len) >> PAGE_SHIFT - ((addr) >> PAGE_SHIFT))
> >
> > > I wonder if there is already a function yielding this value?
> > > Wouldn't
> > >
> > > ((addr + len) >> PAGE_SHIFT) - (addr >> PAGE_SHIFT) + 1
> >
> > No, this won't work (it's not equivalent).
> Ah, this fails if addr + len is page aligned.
>
> ((addr + len - 1) >> PAGE_SHIFT) - (addr >> PAGE_SHIFT) + 1
>
> would work, but I like
>
> (PAGE_ALIGN(addr+len) >> PAGE_SHIFT - ((addr) >> PAGE_SHIFT))
>
> better. (In fact these two are equivalent:
>
> PAGE_ALIGN(addr+len) >> PAGE_SHIFT =
> __ALIGN_KERNEL(addr+len, PAGE_SIZE) >> PAGE_SHIFT =
> __ALIGN_KERNEL_MASK(addr+len, PAGE_SIZE - 1) >> PAGE_SHIFT =
> ((addr + len + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1)) >> PAGE_SHIFT =
> (addr + len + PAGE_SIZE - 1) >> PAGE_SHIFT =
> (addr + len - 1) >> PAGE_SHIFT + 1
>
> Greg: should I send an updated patch or do you modify NUM_PAGES_SPANNED
> accordingly?

Can you please send a new patch?

thanks,

greg k-h
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