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From: Christoph Hellwig <hch@lst.de>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Christoph Hellwig <hch@lst.de>,
	linuxppc-dev@lists.ozlabs.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation
Date: Wed, 28 Oct 2020 18:21:06 +0100	[thread overview]
Message-ID: <20201028172106.GA10015@lst.de> (raw)
In-Reply-To: <28147035-500d-f3cd-f283-257066343697@ozlabs.ru>

On Wed, Oct 28, 2020 at 05:55:23PM +1100, Alexey Kardashevskiy wrote:
>
> It is passing an address of the end of the mapped area so passing a page 
> struct means passing page and offset which is an extra parameter and we do 
> not want to do anything with the page in those hooks anyway so I'd keep it 
> as is.
>
>
>> and
>>     maybe even hide the dma_map_direct inside it.
>
> Call dma_map_direct() from arch_dma_map_page_direct() if 
> arch_dma_map_page_direct() is defined? Seems suboptimal as it is going to 
> be bypass=true in most cases and we save one call by avoiding calling 
> arch_dma_map_page_direct(). Unless I missed something?

C does not even evaluate the right hand side of a || expression if the
left hand evaluates to true.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
	Christoph Hellwig <hch@lst.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation
Date: Wed, 28 Oct 2020 18:21:06 +0100	[thread overview]
Message-ID: <20201028172106.GA10015@lst.de> (raw)
In-Reply-To: <28147035-500d-f3cd-f283-257066343697@ozlabs.ru>

On Wed, Oct 28, 2020 at 05:55:23PM +1100, Alexey Kardashevskiy wrote:
>
> It is passing an address of the end of the mapped area so passing a page 
> struct means passing page and offset which is an extra parameter and we do 
> not want to do anything with the page in those hooks anyway so I'd keep it 
> as is.
>
>
>> and
>>     maybe even hide the dma_map_direct inside it.
>
> Call dma_map_direct() from arch_dma_map_page_direct() if 
> arch_dma_map_page_direct() is defined? Seems suboptimal as it is going to 
> be bypass=true in most cases and we save one call by avoiding calling 
> arch_dma_map_page_direct(). Unless I missed something?

C does not even evaluate the right hand side of a || expression if the
left hand evaluates to true.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
	Christoph Hellwig <hch@lst.de>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation
Date: Wed, 28 Oct 2020 18:21:06 +0100	[thread overview]
Message-ID: <20201028172106.GA10015@lst.de> (raw)
In-Reply-To: <28147035-500d-f3cd-f283-257066343697@ozlabs.ru>

On Wed, Oct 28, 2020 at 05:55:23PM +1100, Alexey Kardashevskiy wrote:
>
> It is passing an address of the end of the mapped area so passing a page 
> struct means passing page and offset which is an extra parameter and we do 
> not want to do anything with the page in those hooks anyway so I'd keep it 
> as is.
>
>
>> and
>>     maybe even hide the dma_map_direct inside it.
>
> Call dma_map_direct() from arch_dma_map_page_direct() if 
> arch_dma_map_page_direct() is defined? Seems suboptimal as it is going to 
> be bypass=true in most cases and we save one call by avoiding calling 
> arch_dma_map_page_direct(). Unless I missed something?

C does not even evaluate the right hand side of a || expression if the
left hand evaluates to true.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2020-10-28 22:07 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-27 10:18 [PATCH kernel v2 0/2] DMA, powerpc/dma: Fallback to dma_ops when persistent memory present Alexey Kardashevskiy
2020-10-27 10:18 ` Alexey Kardashevskiy
2020-10-27 10:18 ` Alexey Kardashevskiy
2020-10-27 10:18 ` [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation Alexey Kardashevskiy
2020-10-27 10:18   ` Alexey Kardashevskiy
2020-10-27 10:18   ` Alexey Kardashevskiy
2020-10-27 16:48   ` Christoph Hellwig
2020-10-27 16:48     ` Christoph Hellwig
2020-10-27 16:48     ` Christoph Hellwig
2020-10-28  6:55     ` Alexey Kardashevskiy
2020-10-28  6:55       ` Alexey Kardashevskiy
2020-10-28  6:55       ` Alexey Kardashevskiy
2020-10-28 17:21       ` Christoph Hellwig [this message]
2020-10-28 17:21         ` Christoph Hellwig
2020-10-28 17:21         ` Christoph Hellwig
2020-10-28 23:11         ` Alexey Kardashevskiy
2020-10-28 23:11           ` Alexey Kardashevskiy
2020-10-28 23:11           ` Alexey Kardashevskiy
2020-10-27 10:18 ` [PATCH kernel v2 2/2] powerpc/dma: Fallback to dma_ops when persistent memory present Alexey Kardashevskiy
2020-10-27 10:18   ` Alexey Kardashevskiy
2020-10-27 10:18   ` Alexey Kardashevskiy

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