lkml.org 
[lkml]   [2014]   [Nov]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: CMA alignment question
From
On Thu, Nov 6, 2014 at 6:01 AM, Michal Nazarewicz <mina86@mina86.com> wrote:
>> On Tue, Nov 04 2014, Gregory Fong wrote:
>>> The alignment in cma_alloc() is done w.r.t. the bitmap. This is a
>>> problem when, for example:
>>>
>>> - a device requires 16M (order 12) alignment
>>> - the CMA region is not 16 M aligned
>
> On Wed, Nov 05 2014, Weijie Yang wrote:
>> I think the device driver should ensure that situation could not occur,
>> by assign suitable alignment parameter in cma_declare_contiguous().
>
> What about default CMA area? Besides, I think principle of least
> surprise applies here and alignment should be physical.

I agree the current code doesn't handle this issue properly.
However, I prefer to add specific usage to CMA interface rather than
modify the cma code, Because the latter hide the issue and could waste
memory.

> --
> Best regards, _ _
> .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
> ..o | Computer Science, Michał “mina86” Nazarewicz (o o)
> ooo +--<mpn@google.com>--<xmpp:mina86@jabber.org>--ooO--(_)--Ooo--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2014-11-06 02:41    [W:0.167 / U:0.260 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site