netdev - Re: [RFC PATCH v2 1/2] net: af_packet support for direct ring access in user space

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Message-Id: <20150113.122733.1459000731112321026.davem@davemloft.net>
Date:	Tue, 13 Jan 2015 12:27:33 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	David.Laight@...LAB.COM
Cc:	john.fastabend@...il.com, dborkman@...hat.com,
	hannes@...essinduktion.org, netdev@...r.kernel.org,
	danny.zhou@...el.com, nhorman@...driver.com,
	john.ronciak@...el.com, brouer@...hat.com
Subject: Re: [RFC PATCH v2 1/2] net: af_packet support for direct ring
 access in user space

From: David Laight <David.Laight@...LAB.COM>
Date: Tue, 13 Jan 2015 17:15:30 +0000

> How about something like:
> 
> struct tpacket_dma_mem_region {
>     __u64 addr;        /* userspace virtual address */
>     __u64 phys_addr;    /* physical address */
>     __u64 iova;        /* IO virtual address used for DMA */
>     __u64 size;    /* size of region */
>     int direction;        /* dma data direction */
> } aligned(8);
> 
> So that it is independant of 32/64 bits.
> It is a shame that gcc has no way of defining a 64bit 'void *' on 32bit systems.
> You can use a union, but you still need to zero extend the value on LE (worse on BE).

We have an __aligned_u64, please use that.
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