linux-kernel - Re: [PATCH v1] dma: imx-sdma: add support for sdma memory copy

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Date:	Tue, 22 Apr 2014 14:24:24 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Robin Gong <b38343@...escale.com>
Cc:	"Koul, Vinod" <vinod.koul@...el.com>,
	"Williams, Dan J" <dan.j.williams@...el.com>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	RandyDunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v1] dma: imx-sdma: add support for sdma memory copy

On Tue, 2014-04-22 at 18:51 +0800, Robin Gong wrote:
> On Tue, Apr 22, 2014 at 10:28:05AM +0000, Shevchenko, Andriy wrote:
> > On Fri, 2014-04-18 at 17:41 +0800, Robin Gong wrote:
> > > On Thu, Apr 17, 2014 at 10:24:50AM +0000, Shevchenko, Andriy wrote:
> > > > On Thu, 2014-04-17 at 18:01 +0800, Robin Gong wrote:
> > 
> > []
> > 
> > > > > +	dev_dbg(sdma->dev, "memcpy: %x->%x, len=%d, channel=%d.\n",
> > > > 
> > > > %pad for dma_addr_t variables.
> > > >
> > > Yes, %x here is not proper, will be %#llx here to align with others similar
> > > code in this file.
> > 
> > Why %#llx? You don't need the specific casting since kernel has special
> > specifiers for phys_addr_t and dma_addr_t and their derivatives (see
> > Documentation/printk-formats.txt)
> >
> I think both are ok, why I choose %llx is only for align the code style,

Yes, but it was started being developed earlier than kernel gains the
feature.

>  you
> can find the same code in sdma_prep_dma_cyclic function. below description also
> copy from Documentation/printk-formats.txt:
> 
> 
> If <type> is dependent on a config option for its size (e.g., sector_t,
> blkcnt_t, phys_addr_t, resource_size_t) or is architecture-dependent
> for its size (e.g., tcflag_t), use a format specifier of its largest
> possible type and explicitly cast to it.  Example:
> 
> 	printk("test: sector number/total blocks: %llu/%llu\n",
> 		(unsigned long long)sector, (unsigned long long)blockcount);

Yeah, I think it requires to be updated accordingly to last changes
regarding to new specifiers.

+Cc Randy. Randy, do you think is a matter of fact that we have to
update that paragraph somehow and recommend to prefer special specifiers
over explicit casting to longest possible type?

> > > > > +		dev_dbg(sdma->dev, "entry %d: count: %d dma: 0x%08x %s%s\n",
> > > > > +				i, count, sg_src->dma_address,
> > > > 
> > > > %pad for dma_addr_t.
> > > > 
> > > Accept the idea, same as the above.
> > 
> > Same as above.


-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy

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