linux-kernel - Re: [PATCHv2 4/4] ARM: dma-mapping: remove custom consistent dma region

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Date:	Wed, 30 May 2012 03:22:53 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
CC:	'KOSAKI Motohiro' <kosaki.motohiro@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	'Kyungmin Park' <kyungmin.park@...sung.com>,
	'Arnd Bergmann' <arnd@...db.de>,
	'Russell King - ARM Linux' <linux@....linux.org.uk>,
	'Chunsang Jeong' <chunsang.jeong@...aro.org>,
	'Krishna Reddy' <vdumpa@...dia.com>,
	'Konrad Rzeszutek Wilk' <konrad.wilk@...cle.com>,
	'Hiroshi Doyu' <hdoyu@...dia.com>,
	'Subash Patel' <subashrp@...il.com>
Subject: Re: [PATCHv2 4/4] ARM: dma-mapping: remove custom consistent dma
 region

(5/30/12 3:15 AM), Marek Szyprowski wrote:
> Hello,
>
> On Wednesday, May 30, 2012 2:11 AM KOSAKI Motohiro wrote:
>
>>>    static void *
>>>    __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
>>>    	const void *caller)
>>>    {
>>> -	struct arm_vmregion *c;
>>> -	size_t align;
>>> -	int bit;
>>> +	struct vm_struct *area;
>>> +	unsigned long addr;
>>>
>>> -	if (!consistent_pte) {
>>> -		printk(KERN_ERR "%s: not initialised\n", __func__);
>>> +	area = get_vm_area_caller(size, VM_DMA | VM_USERMAP, caller);
>>
>> In this patch, VM_DMA is only used here. So, is this no effect?
>
> I introduced it mainly to let user know which areas have been allocated by the dma-mapping api.

vma->flags are limited resource, it has only 32 (or 64) bits. Please don't use it for such unimportant
thing.


> I also plan to add a check suggested by Minchan Kim in __dma_free_remap() if the vmalloc area
> have been in fact allocated with VM_DMA set.


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