looking into kernel source, it seemed quite simple:
./sound/pci/emu10k1/memory.c:
#define get_aligned_page(offset) ((offset) >> PAGE_SHIFT)
blk->first_page = get_aligned_page(blk->mem.offset);
blk->last_page = get_aligned_page(blk->mem.offset + blk->mem.size - 1);
psize = get_aligned_page(size + PAGE_SIZE -1);
page = get_aligned_page(offset);
./sound/pci/trident/trident_memory.c:
#define get_aligned_page(offset) ((offset) >> 12)
#define get_aligned_page(offset) ((offset) >> 13)
#define get_aligned_page(offset) ((offset) / ALIGN_PAGE_SIZE)
ptr = page_to_ptr(trident, get_aligned_page(offset));
psize = get_aligned_page(size + ALIGN_PAGE_SIZE -1);
ie, just AND with the alignement requirement.
And the trident_memory.c:is_valid_page() function worked like this:
/*
* check if the given pointer is valid for pages
*/
static int is_valid_page(unsigned long ptr)
{
if (ptr & ~0x3fffffffUL) {
snd_printk(KERN_ERR "max memory size is 1GB!!\n");
return 0;
}
if (ptr & (SNDRV_TRIDENT_PAGE_SIZE-1)) {
snd_printk(KERN_ERR "page is not aligned\n");
return 0;
}
return 1;
}
So, as the last part shows, just AND the address with the alignment
requirement will do.
But I have not looked else where.
On Tue, Feb 17, 2009 at 9:53 AM, Pei Lin <[email protected]> wrote:
> >>And kmalloc is page aligned, "4096/16 = 256", is it also 16 aligned?
>
> >>>Maybe i misunderstand about "aligned" meaning.
>
> Oh,sorry vmalloc is page aligned kmalloc is not.
>
>
> 2009/2/17 Pei Lin <[email protected]>:
> > i think slab can do that,look at
> > mm/slab.c:
> > "struct kmem_cache *
> > kmem_cache_create (const char *name, size_t size, size_t align,
> > unsigned long flags,
> > void (*ctor)(struct kmem_cache *, void *))"
> >
> > the parameter "align" for what?
> >
> > And kmalloc is page aligned, "4096/16 = 256", is it also 16 aligned?
> >
> > Maybe i misunderstand about "aligned" meaning.
> >
> >
> >
> > 2009/2/16 Mulyadi Santosa <[email protected]>:
> >> On Sun, Feb 15, 2009 at 4:41 PM, Ramagudi Naziir <[email protected]>
> wrote:
> >>> hello everyone
> >>>
> >>> i need to allocate memory aligned 16 bytes.
> >>>
> >>> how can i do that ?
> >>>
> >>> can I use kmalloc for that ?
> >>
> >> Uhm, kmalloc use slab so I don't think it will be aligned. My wild
> >> guess is you have use alloc_page(s) or use _aligned_ (or _align_?...
> >> not sure) gcc builtin directive
> >>
> >> regards,
> >>
> >> Mulyadi.
> >>
> >> --
> >> To unsubscribe from this list: send an email with
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> >> Please read the FAQ at http://kernelnewbies.org/FAQ
> >>
> >>
> >
>
> --
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>
--
Regards,
Peter Teoh
