linux-kernel - Re: [PATCH] usb: musb: use the new %pa format specifier for dma_addr

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Date:	Sat, 01 Jun 2013 14:56:47 -0700
From:	Randy Dunlap <rdunlap@...radead.org>
To:	Joe Perches <joe@...ches.com>
CC:	Emil Goode <emilgoode@...il.com>,
	Stepan Moskovchenko <stepanm@...eaurora.org>, balbi@...com,
	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] usb: musb: use the new %pa format specifier for dma_addr_t

On 06/01/13 13:31, Joe Perches wrote:
> On Sat, 2013-06-01 at 21:09 +0200, Emil Goode wrote:
>> I see, will send a second version.
> 
> Hey Emil.
> 
> I believe you can not use %pa with a dma_addr_t
> because that could be a different size than a
> phy_addr_t.
> 
> (the vsprintf cast and deref is to a phy_addr_t)

Hi Joe,

Thank you for pointing that out.  It's a bit of a shame that this
comment was deleted from include/asm-generic/types.h in commit
3e50594e8e72932ad4cfcb0b3cbdf58fc3bce416:

-/*
- * DMA addresses may be very different from physical addresses
- * and pointers. i386 and powerpc may have 64 bit DMA on 32 bit
- * systems, while sparc64 uses 32 bit DMA addresses for 64 bit
- * physical addresses.
- * This default defines dma_addr_t to have the same size as
- * phys_addr_t, which is the most common way.
- * Do not define the dma64_addr_t type, which never really
- * worked.
- */


> The definitions are: (types.h)
> 
> #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
> typedef u64 dma_addr_t;
> #else
> typedef u32 dma_addr_t;
> #endif /* dma_addr_t */
> 
> []
> 
> #ifdef CONFIG_PHYS_ADDR_T_64BIT
> typedef u64 phys_addr_t;
> #else
> typedef u32 phys_addr_t;
> #endif
> 
> On Sat, Jun 01, 2013 at 11:29:10AM -0700, Joe Perches wrote:
>> On Sat, 2013-06-01 at 20:02 +0200, Emil Goode wrote:
>>> This patch makes use of the new format specifier %pa that was introduced
>>> by the following commit.
>>>
>>> 7d7992108d02aa92ad4c77e5d9ce14088c942e75
>>> ("lib/vsprintf.c: add %pa format specifier for phys_addr_t types")
>> []
>>> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
>> []
>>> @@ -1756,12 +1756,11 @@ void musb_host_rx(struct musb *musb, u8 epnum)
>> []
>>> -                   dev_dbg(musb->controller, "RX%d count %d, buffer 0x%llx len %d/%d\n",
>>> +                   dev_dbg(musb->controller, "RX%d count %d, buffer 0x%pa len %d/%d\n",
>>
>> This would emit 0x0x<addr>


-- 
~Randy
--
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