linux-kernel - Re: [PATCH][v2] uio: Support 36-bit physical addresses on 32-bit systems

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Message-Id: <9BD33578-CD8E-4784-AC6A-ADE4614E0FC1@kernel.crashing.org>
Date:	Thu, 13 Oct 2011 10:32:51 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Tabi Timur-B04825 <B04825@...escale.com>
Cc:	"hjk@...sjkoch.de" <hjk@...sjkoch.de>,
	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	"gregkh@...e.de" <gregkh@...e.de>,
	Jiang Kai-B18973 <B18973@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][v2] uio: Support 36-bit physical addresses on 32-bit systems


On Oct 13, 2011, at 9:37 AM, Tabi Timur-B04825 wrote:

> On Wed, Oct 12, 2011 at 3:57 PM, Kumar Gala <galak@...nel.crashing.org> wrote:
>> From: Kai Jiang <Kai.Jiang@...escale.com>
>> 
>> To support >32-bit physical addresses for UIO_MEM_PHYS type we need to
>> extend the width of 'addr' in struct uio_mem.  Numerous platforms like
>> embedded PPC, ARM, and X86 have support for systems with larger physical
>> address than logical.
>> 
>> Since 'addr' may contain a physical, logical, or virtual address the
>> easiest solution is to just change the type to 'unsigned long long'
>> regardless of which type is utilized.
> 
> You forgot to update this description.

will fix and update commit message

> 
>>  struct uio_mem {
>>        const char              *name;
>> -       unsigned long           addr;
>> +       phys_addr_t             addr;
> 
> Please add a comment here saying:
> 
> 1) That 'addr' can be a virtual or physical address

The code and everything else makes that clear

> 2) That the kernel guarantees that sizeof(phys_addr_t) >= sizeof(void
> *), so it's safe to use phys_addr_t for a virtual pointer.

The commit message will cover that so I don't plan on add it.

- k--
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