Re: how to allocate 9MB of memory in kernel ?

From: Marco Stornelli <marco.stornelli@coritel•it>
To: Misbah khan <misbah_khan@engineer•com>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: how to allocate 9MB of memory in kernel ?
Date: Fri, 18 Jul 2008 08:50:36 +0200	[thread overview]
Message-ID: <48803D3C.5020608@coritel.it> (raw)
In-Reply-To: <18522535.post@talk.nabble.com>

Misbah khan ha scritto:
> This i am not very sure with  :-
> Can we allocate 9MB using vmalloc and assure it to be low memory and not
> highmem ?

Why do you need only low memory? And why do you need to allocate memory? 
If I understood correctly you need only to "ioremap" a chunk of memory.

> can we ioremap 9 MB SDRAM to kernel virtual ?

Yep.

> can we use vmalloc and do mmap to that allocated memory ,if the pages are
> not continues then is it going to concern mapping to user space ?

The "contiguous" problem is related only to DMA operations.

> 
> ---Misbah <><
> 
> 
> 
> Arnd Bergmann wrote:
>> On Thursday 17 July 2008, Misbah khan wrote:
>>> I need to allocate 9 MB of memory in to the kernel space which i need to
>>> mmap for the application to access.
>>>
>>> I need to know what could be the best possible way of doing the same.
>>>
>> If you don't need the memory to be physically contiguous, you can use
>> vmalloc to get the memory, but then you need to use remap_vmalloc_range
>> for mapping the memory into a user address space.
>>
>> 	Arnd <><
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>>
> 

-- 
Marco Stornelli
Embedded Software Engineer
CoRiTeL - Consorzio di Ricerca sulle Telecomunicazioni
http://www.coritel.it

marco.stornelli@coritel•it
+39 06 72582838