linux-kernel - Re: Some questions about high memory

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Message-ID: <CANudz+up6=6Zx-9=7QndLqbbBLrApJG5C87ukWorpkisiK5bdw@mail.gmail.com>
Date:	Fri, 6 Apr 2012 14:21:38 +0800
From:	loody <miloody@...il.com>
To:	Mulyadi Santosa <mulyadi.santosa@...il.com>
Cc:	kernelnewbies@...nelnewbies.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Some questions about high memory

hi mulyadi

2012/4/6 Mulyadi Santosa <mulyadi.santosa@...il.com>:
> Hi...
>
> On Fri, Apr 6, 2012 at 09:19, loody <miloody@...il.com> wrote:
>> hi all:
>> I am trying to write a driver for my block device which dma support
>> high memory copying.
>> I have register my device as "blk_bounce_any".
>> But my driver cannot see block layer pass high memory to me so far.
>
> perhaps because you need to kmap them first?
If I remember correctly, Kmap is used for mapping high memory into
kernel virtual memory.
Isn't that the job for block layer?

I thought once I declare my block device as "blk_bounce_any", the
block layer will pass the physical address of high memory to device.


>
> BTW, is it 32 bit or 64 bit Linux kernel?
32-bits linux kernel.

>
>> Is there any user/kernel test program which will purposely send high
>> memory for driver to use?
>> or is there any flag when opening a file in user mode that will use high memory?
>
> I recheck mmap and mmap manual page and I found none of such flag

does that mean mmap can specify which memory to map?
if that is true, which range I should use?

>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com

Appreciate your help
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