From: Al Viro <viro@ZenIV•linux.org.uk>
To: Jie Deng <Jie.Deng1@synopsys•com>
Cc: netdev@vger•kernel.org
Subject: Re: [RFC][PATCH] apparent big-endian bugs in dwc-xlgmac
Date: Mon, 11 Dec 2017 05:05:20 +0000 [thread overview]
Message-ID: <20171211050520.GV21978@ZenIV.linux.org.uk> (raw)
In-Reply-To: <420a198d-61f8-81cf-646d-10446cb41def@synopsys.com>
On Mon, Dec 11, 2017 at 12:33:42PM +0800, Jie Deng wrote:
> Hi AI Viro,
> > @@ -125,8 +125,8 @@
> > typeof(len) _len = (len); \
> > typeof(val) _val = (val); \
> > _val = (_val << _pos) & GENMASK(_pos + _len - 1, _pos); \
> > - _var = (_var & ~GENMASK(_pos + _len - 1, _pos)) | _val; \
> > - cpu_to_le32(_var); \
> > + (_var & ~cpu_to_le32(GENMASK(_pos + _len - 1, _pos))) | \
> > + cpu_to_le32(_val); \
> > })
> >
> > struct xlgmac_pdata;
>
> Make sense. But I think what you want is fix as follows. Right ?
>
> @@ -125,8 +125,8 @@
> typeof(len) _len = (len); \
> - typeof(val) _val = (val); \
> + u32 _var = le32_to_cpu((var)); \
> _val = (_val << _pos) & GENMASK(_pos + _len - 1, _pos); \
> - _var = (_var & ~GENMASK(_pos + _len - 1, _pos)) | _val; \
> - cpu_to_le32(_var); \
> + (cpu_to_le32(_var) & ~cpu_to_le32(GENMASK(_pos + _len - 1, _pos))) | \
> + cpu_to_le32(_val); \
> })
What for? Sure, this variant will work, but why bother with
a = le32_to_cpu(b);
(cpu_to_le32(a) & ....) | ....
and how is that better than
(b & ...) | ...
IDGI... Mind you, I'm not sure if there is any point keeping _var in that thing,
seeing that we use var only once - might be better off with
((var) & ~cpu_to_le32(GENMASK(_pos + _len - 1, _pos))) | \
cpu_to_le32(_val); \
next prev parent reply other threads:[~2017-12-11 5:05 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-10 4:53 [RFC][PATCH] apparent big-endian bugs in dwc-xlgmac Al Viro
2017-12-11 4:33 ` Jie Deng
2017-12-11 5:05 ` Al Viro [this message]
2017-12-11 5:38 ` Al Viro
2017-12-11 6:46 ` Jie Deng
2017-12-11 15:54 ` [RFC][PATCH] new byteorder primitives - ..._{replace,get}_bits() Al Viro
2017-12-12 4:02 ` Jakub Kicinski
2017-12-12 6:20 ` Al Viro
2017-12-12 19:45 ` Al Viro
2017-12-12 20:04 ` Jakub Kicinski
2017-12-12 23:48 ` Al Viro
2017-12-12 23:59 ` Jakub Kicinski
2017-12-13 0:36 ` Al Viro
2017-12-13 1:04 ` Jakub Kicinski
2017-12-13 1:30 ` Al Viro
2017-12-13 1:35 ` Jakub Kicinski
2017-12-13 1:51 ` Al Viro
2017-12-13 2:44 ` Jakub Kicinski
2017-12-13 14:22 ` Al Viro
2017-12-13 17:45 ` Al Viro
2017-12-15 2:33 ` [RFC][PATCH] Add primitives for manipulating bitfields both in host- and fixed-endian Al Viro
2017-12-15 5:07 ` Jakub Kicinski
2017-12-15 5:34 ` Al Viro
2017-12-15 16:48 ` [RFC][PATCH v2] " Al Viro
2017-12-13 19:04 ` [RFC][PATCH] new byteorder primitives - ..._{replace,get}_bits() Jakub Kicinski
2017-12-11 6:18 ` [RFC][PATCH] apparent big-endian bugs in dwc-xlgmac Jie Deng
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