linux-kernel - RE: [PATCH V2 1/3] NTB: Add AMD PCI-Express NTB driver

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Message-ID: <BLUPR12MB04201B8AB79A25C8173863C4EBC90@BLUPR12MB0420.namprd12.prod.outlook.com>
Date:	Mon, 11 Jan 2016 07:07:51 +0000
From:	"Yu, Xiangliang" <Xiangliang.Yu@....com>
To:	Allen Hubbe <Allen.Hubbe@....com>, 'Jon Mason' <jdmason@...zu.us>
CC:	'Dave Jiang' <dave.jiang@...el.com>,
	"linux-ntb@...glegroups.com" <linux-ntb@...glegroups.com>,
	'linux-kernel' <linux-kernel@...r.kernel.org>,
	SPG_Linux_Kernel <SPG_Linux_Kernel@....com>
Subject: RE: [PATCH V2 1/3] NTB: Add AMD PCI-Express NTB driver

> From: Jon Mason <jdmason@...zu.us>
> > On Wed, Jan 6, 2016 at 9:50 PM, Yu, Xiangliang <Xiangliang.Yu@....com>
> > wrote:
> > >> > +#define NTB_READ_REG(base, r) (ioread32(base + AMD_ ## r ##
> > >> _OFFSET))
> > >> > +#define NTB_WRITE_REG(base, val, r) (iowrite32(val, base +     \
> > >> > +                                               AMD_ ## r ##
> > _OFFSET))
> > >> > +#define NTB_READ_OFFSET(base, r, of) (ioread32(base + of +
> > \
> > >> > +                                               AMD_ ## r ##
> > _OFFSET))
> > >> > +#define NTB_WRITE_OFFSET(base, val, r, of) (iowrite32(val, base
> > >> > ++
> > \
> > >> > +                                               of + AMD_ ## r ##
> > _OFFSET))
> > >>
> > >> Please do not use marcos to hide ioread/iowrite.  Call
> > >> iorwad/iowrite
> > directly.
> > >
> > > I don't see any wrong to hide ioread/iowrite, and I think the macros
> > can make code readable and easy to maintain.
> >
> > I disagree.  It is an unnecessary layer and can add to confusion.
> > Please make the change.
> 
> I don't like AMD_##r##_OFFSET in these macros.  It hides the use of a
> globally named constant like AMD_FOO_OFFSET, since one would read only
> FOO in the code.  It makes cross referencing difficult, since the reader needs
> to know FOO is really AMD_FOO_OFFSET.  This would defeat automatic cross
> referencing like cscope and lxr.
> 
> #define AMD_FOO_OFFSET 0xc0ff33
> vs
> NTB_READ_OFFSET(dev->foo_base, FOO, offset_in_foo) // Where is FOO
> defined?
> 
> This macro would have at least been better written without ##; so cross
> referencing would still work.
> 
> NTB_READ_OFFSET(dev->foo_base, FOO, offset_in_foo) vs
> NTB_READ_OFFSET(dev->foo_base, AMD_FOO_OFFSET, offset_in_foo) //
> AMD_FOO_OFFSET is 0xcoff33 (obviously)
> 
> But without ##, the macro is just the addition of its parameters.  Change the
> commas to addition, and the macro to ioread, and you'll see there is no
> benefit for having this macro any more.
> 
> NTB_READ_OFFSET(dev->foo_base, AMD_FOO_OFFSET, offset_in_foo) vs
> ioread32(dev->foo_base + AMD_FOO_OFFSET + offset_in_foo)
> 
> I second Jon's opinion.  Please make the change.  This would be better as
> simply ioread/write in the code.

The main aim of these macros is to focuses on the name of register (FOO), 
not the whole macros of register. 
and I see there are lots of these style in kernel.
If your guys still can't accept the style, I can change it. 
And I'll change ioread/iowrite to readl/writel because it only access mmio space.