From: "Christian König" <christian.koenig@amd.com>
To: David Miller <davem@davemloft.net>
Cc: alexander.deucher@amd.com, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] radeon: Do not directly dereference pointers to BIOS area.
Date: Fri, 20 Mar 2015 10:38:32 +0100 [thread overview]
Message-ID: <550BEA98.8010609@amd.com> (raw)
In-Reply-To: <20150319.122906.969543288532051737.davem@davemloft.net>
On 19.03.2015 17:29, David Miller wrote:
> From: Christian König <christian.koenig@amd.com>
> Date: Thu, 19 Mar 2015 09:50:58 +0100
>
>> In general I would say yes, but for this particular hardware it's a
>> bit questionable to do so.
>>
>> For radeon hardware to work correctly the CPU access to the PCIE BARs
>> should work even without using the specialized IO macros/functions,
>> otherwise mapping VRAM CPU accessible isn't really possible.
>>
>> What's the background of the change? Some problems on a certain CPU
>> platform? or just general cleanups?
> It's an _iomem_ pointer, it's not a virtual address.
>
> Therefore it is illegal to dereference the pointer.
>
> The value is opaque and has values that only make sense when used
> with the readb() et al. interfaces.
>
> This code is relying upon the fact that on x86 it happens to be
> a virtual address, but this won't work on many other architectures.
In this case I'm perfectly fine with it and the patch is Reviewed-by:
Christian König <christian.koenig@amd.com>
Just wanted to make sure that you're not trying to get Radeon working on
a platform which will never really support the necessary hardware features.
Regards,
Christian.
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WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <christian.koenig@amd.com>
To: David Miller <davem@davemloft.net>
Cc: <alexander.deucher@amd.com>, <dri-devel@lists.freedesktop.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] radeon: Do not directly dereference pointers to BIOS area.
Date: Fri, 20 Mar 2015 10:38:32 +0100 [thread overview]
Message-ID: <550BEA98.8010609@amd.com> (raw)
In-Reply-To: <20150319.122906.969543288532051737.davem@davemloft.net>
On 19.03.2015 17:29, David Miller wrote:
> From: Christian König <christian.koenig@amd.com>
> Date: Thu, 19 Mar 2015 09:50:58 +0100
>
>> In general I would say yes, but for this particular hardware it's a
>> bit questionable to do so.
>>
>> For radeon hardware to work correctly the CPU access to the PCIE BARs
>> should work even without using the specialized IO macros/functions,
>> otherwise mapping VRAM CPU accessible isn't really possible.
>>
>> What's the background of the change? Some problems on a certain CPU
>> platform? or just general cleanups?
> It's an _iomem_ pointer, it's not a virtual address.
>
> Therefore it is illegal to dereference the pointer.
>
> The value is opaque and has values that only make sense when used
> with the readb() et al. interfaces.
>
> This code is relying upon the fact that on x86 it happens to be
> a virtual address, but this won't work on many other architectures.
In this case I'm perfectly fine with it and the patch is Reviewed-by:
Christian König <christian.koenig@amd.com>
Just wanted to make sure that you're not trying to get Radeon working on
a platform which will never really support the necessary hardware features.
Regards,
Christian.
next prev parent reply other threads:[~2015-03-20 9:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 3:18 [PATCH] radeon: Do not directly dereference pointers to BIOS area David Miller
2015-03-19 8:50 ` Christian König
2015-03-19 8:50 ` Christian König
2015-03-19 16:29 ` David Miller
2015-03-20 9:38 ` Christian König [this message]
2015-03-20 9:38 ` Christian König
2015-03-20 13:50 ` Alex Deucher
2015-03-20 17:24 ` David Miller
2015-03-20 17:39 ` Deucher, Alexander
2015-03-20 17:39 ` Deucher, Alexander
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