From: Andrew Morton <akpm@linux-foundation.org>
To: Brian Starkey <brian.starkey@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Dan Williams <dan.j.williams@intel.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RESEND2 PATCH 1/3] memremap: add MEMREMAP_WC flag
Date: Mon, 8 Feb 2016 12:03:17 -0800 [thread overview]
Message-ID: <20160208120317.313409dc0ae7634c25d3f021@linux-foundation.org> (raw)
In-Reply-To: <9085d37fa97a762a46b9d58719c085368682c64f.1454950917.git.brian.starkey@arm.com>
On Mon, 8 Feb 2016 17:30:50 +0000 Brian Starkey <brian.starkey@arm.com> wrote:
> Add a flag to memremap() for writecombine mappings. Mappings satisfied
> by this flag will not be cached, however writes may be delayed or
> combined into more efficient bursts. This is most suitable for
> buffers written sequentially by the CPU for use by other DMA devices.
>
> ...
The patch generally looks OK to me. It generates rejects against
linux-next because of some janitorial changes in memremap.c.
> @@ -101,6 +107,11 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
> addr = ioremap_wt(offset, size);
> }
>
> + if (!addr && (flags & MEMREMAP_WC)) {
> + flags &= ~MEMREMAP_WC;
> + addr = ioremap_wc(offset, size);
> + }
> +
> return addr;
> }
The modifications of `flags' is unneeded (and the compiler will remove
it). And generally the modification of incoming args is a bit nasty
IMO - I find it's better to treat them as const - part of the calling
environment which can be relied upon to be unaltered as the code
evolves.
WARNING: multiple messages have this Message-ID (diff)
From: akpm@linux-foundation.org (Andrew Morton)
To: linux-arm-kernel@lists.infradead.org
Subject: [RESEND2 PATCH 1/3] memremap: add MEMREMAP_WC flag
Date: Mon, 8 Feb 2016 12:03:17 -0800 [thread overview]
Message-ID: <20160208120317.313409dc0ae7634c25d3f021@linux-foundation.org> (raw)
In-Reply-To: <9085d37fa97a762a46b9d58719c085368682c64f.1454950917.git.brian.starkey@arm.com>
On Mon, 8 Feb 2016 17:30:50 +0000 Brian Starkey <brian.starkey@arm.com> wrote:
> Add a flag to memremap() for writecombine mappings. Mappings satisfied
> by this flag will not be cached, however writes may be delayed or
> combined into more efficient bursts. This is most suitable for
> buffers written sequentially by the CPU for use by other DMA devices.
>
> ...
The patch generally looks OK to me. It generates rejects against
linux-next because of some janitorial changes in memremap.c.
> @@ -101,6 +107,11 @@ void *memremap(resource_size_t offset, size_t size, unsigned long flags)
> addr = ioremap_wt(offset, size);
> }
>
> + if (!addr && (flags & MEMREMAP_WC)) {
> + flags &= ~MEMREMAP_WC;
> + addr = ioremap_wc(offset, size);
> + }
> +
> return addr;
> }
The modifications of `flags' is unneeded (and the compiler will remove
it). And generally the modification of incoming args is a bit nasty
IMO - I find it's better to treat them as const - part of the calling
environment which can be relied upon to be unaltered as the code
evolves.
next prev parent reply other threads:[~2016-02-08 20:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-08 17:30 [RESEND2 PATCH 0/3] Fix kernel panic in dma-coherent Brian Starkey
2016-02-08 17:30 ` Brian Starkey
2016-02-08 17:30 ` [RESEND2 PATCH 1/3] memremap: add MEMREMAP_WC flag Brian Starkey
2016-02-08 17:30 ` Brian Starkey
2016-02-08 18:30 ` Greg Kroah-Hartman
2016-02-08 18:30 ` Greg Kroah-Hartman
2016-02-09 9:15 ` Brian Starkey
2016-02-09 9:15 ` Brian Starkey
2016-02-16 11:14 ` Brian Starkey
2016-02-16 11:14 ` Brian Starkey
2016-02-17 0:43 ` Greg Kroah-Hartman
2016-02-17 0:43 ` Greg Kroah-Hartman
2016-02-17 10:07 ` Brian Starkey
2016-02-17 10:07 ` Brian Starkey
2016-02-08 20:03 ` Andrew Morton [this message]
2016-02-08 20:03 ` Andrew Morton
2016-02-09 10:23 ` Brian Starkey
2016-02-09 10:23 ` Brian Starkey
2016-02-17 11:53 ` Brian Starkey
2016-02-17 11:53 ` Brian Starkey
2016-02-17 19:02 ` Andrew Morton
2016-02-17 19:02 ` Andrew Morton
2016-02-08 17:30 ` [RESEND2 PATCH 2/3] drivers: dma-coherent: use MEMREMAP_WC for DMA_MEMORY_MAP Brian Starkey
2016-02-08 17:30 ` Brian Starkey
2016-02-08 17:30 ` [RESEND2 PATCH 3/3] drivers: dma-coherent: use memset_io for DMA_MEMORY_IO mappings Brian Starkey
2016-02-08 17:30 ` Brian Starkey
2016-02-08 17:50 ` [RESEND2 PATCH 0/3] Fix kernel panic in dma-coherent Mark Rutland
2016-02-08 17:50 ` Mark Rutland
2016-02-08 17:59 ` Robin Murphy
2016-02-08 17:59 ` Robin Murphy
2016-02-08 18:04 ` Mark Rutland
2016-02-08 18:04 ` Mark Rutland
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