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From: Arnd Bergmann <arnd@arndb.de>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: jdmason@kudzu.us, Dave Jiang <dave.jiang@intel.com>,
	Allen.Hubbe@gmail.com, "Hook, Gary" <gary.hook@amd.com>,
	Sergey.Semin@t-platforms.ru, linux-ntb@googlegroups.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] NTB: ntb_perf: fix cast to restricted __le32
Date: Fri, 19 Jan 2018 21:42:17 +0100	[thread overview]
Message-ID: <CAK8P3a3SxeON4m8bjehjNKtX_T75udDFEEXnQ4j2KDe3vKz5vA@mail.gmail.com> (raw)
In-Reply-To: <20180119173044.8013-1-fancer.lancer@gmail.com>

On Fri, Jan 19, 2018 at 6:30 PM, Serge Semin <fancer.lancer@gmail.com> wrote:
> Sparse is whining about the u32 and __le32 mixed usage in the
> driver.
>
> drivers/ntb/test/ntb_perf.c:288:21: warning: cast to restricted __le32
> drivers/ntb/test/ntb_perf.c:295:37: warning: incorrect type in argument 4 (different base types)
> drivers/ntb/test/ntb_perf.c:295:37:    expected unsigned int [unsigned] [usertype] val
> drivers/ntb/test/ntb_perf.c:295:37:    got restricted __le32 [usertype] <noident>
> ...
>
> The NTB API can't be changed so ntb_spad_*() methods
> would return either pure __le32 or __be32, since the scratchpad
> data can have arbitrary endianness in general. In this case we
> need to forcibly cast all the u32 to be __le32 and vise-versa
> where it's supposed to be in accordance with the driver logic.
>

There's got to be a better way to do this than sprinkling lots of __force
typecasts throughout the code.

It looks like all those casts are about
ntb_peer_spad_read()/ntb_peer_msg_write() calls, so why not change
those function prototypes to work on __le32 types?

There should also be some form of documentation regarding why you
need to swap the data twice, since all the ntb drivers later end up
doing another cpu_to_le32() on the little-endian data.

       Arnd

  reply	other threads:[~2018-01-19 20:42 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-19 17:30 [PATCH] NTB: ntb_perf: fix cast to restricted __le32 Serge Semin
2018-01-19 20:42 ` Arnd Bergmann [this message]
2018-01-19 21:03   ` Serge Semin
2018-01-19 21:25     ` Serge Semin
2018-01-19 21:26     ` Arnd Bergmann
2018-01-24  4:18       ` Jon Mason
2018-01-24  7:31         ` Serge Semin
2018-01-24  7:48 ` [PATCH v2] " Serge Semin
2018-01-24  8:07   ` Arnd Bergmann
2018-01-25  4:13     ` Jon Mason

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