From: Neil Armstrong <narmstrong@baylibre.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: "jianxin.pan@amlogic.com" <jianxin.pan@amlogic.com>,
Simon Ser <contact@emersion.fr>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
Kevin Hilman <khilman@baylibre.com>,
"linux-amlogic@lists.infradead.org"
<linux-amlogic@lists.infradead.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v8 1/6] drm/fourcc: Add modifier definitions for describing Amlogic Video Framebuffer Compression
Date: Thu, 2 Jul 2020 17:11:25 +0200 [thread overview]
Message-ID: <190ac909-c78b-81e0-35a1-353cd24e9f44@baylibre.com> (raw)
In-Reply-To: <CAKMK7uHa4ajC5_SA_fFUhB-Amxcbt7T9UZ+pvRhqDeUeX9Ez6A@mail.gmail.com>
Hi,
On 02/07/2020 16:15, Daniel Vetter wrote:
> On Thu, Jul 2, 2020 at 3:34 PM Neil Armstrong <narmstrong@baylibre.com> wrote:
>>
>> On 02/07/2020 15:18, Daniel Vetter wrote:
>>> On Thu, Jul 02, 2020 at 09:23:11AM +0000, Simon Ser wrote:
>>>> On Thursday, July 2, 2020 9:47 AM, Neil Armstrong <narmstrong@baylibre.com> wrote:
>>>>
>>>>> Finally is also adds the Scatter Memory layout, meaning the header contains IOMMU
>>>>> references to the compressed frames content to optimize memory access
>>>>> and layout.
>>>>>
>>>>> In this mode, only the header memory address is needed, thus the content
>>>>> memory organization is tied to the current producer execution and cannot
>>>>> be saved/dumped neither transferrable between Amlogic SoCs supporting this
>>>>> modifier.
>>>>
>>>> Still not sure how to handle this one, since this breaks fundamental
>>>> assumptions about modifiers.
>>>
>>> I wonder whether we should require special allocations for these, and then
>>> just outright reject mmap on these buffers. mmap on dma-buf isn't a
>>> required feature.
>>
>> Yes, it's the plan to reject mmap on these buffers, but it can't be explained
>> in the modifiers description and it's a requirement of the producer, not the
>> consumer.
>
> Hm I think worth to add that as a note to the modifier. Just to make
> sure. And avoids questions like the one from Simon.
Something like:
/*
* Amlogic FBC Scatter Memory layout
*
* Indicates the header contains IOMMU references to the compressed
* frames content to optimize memory access and layout.
*
* In this mode, only the header memory address is needed, thus the
* content memory organization is tied to the current producer
* execution and cannot be saved/dumped neither transferrable between
* Amlogic SoCs supporting this modifier.
+ *
+ * Due to the nature of the layout, these buffers are not expected to
+ * be accessible by the user-space clients but only accessible by the
+ * hardware producers and consumers.
+ *
+ * The user-space clients should expect a failure while trying to mmap
+ * the DMA-BUF handle returned by the producer.
*/
Thanks,
Neil
> -Daniel
>
>>
>>>
>>> That would make sure that userspace cannot look at them.
>>>
>>> Also I'm kinda suspecting that there's not unlimited amounts of this magic
>>> invisible storage available anyway.
>>> -Daniel
>>>
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
>
>
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next prev parent reply other threads:[~2020-07-02 15:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 7:47 [PATCH v8 0/6] drm/meson: add support for Amlogic Video FBC Neil Armstrong
2020-07-02 7:47 ` [PATCH v8 1/6] drm/fourcc: Add modifier definitions for describing Amlogic Video Framebuffer Compression Neil Armstrong
2020-07-02 9:23 ` Simon Ser
2020-07-02 13:18 ` Daniel Vetter
2020-07-02 13:34 ` Neil Armstrong
2020-07-02 14:15 ` Daniel Vetter
2020-07-02 15:11 ` Neil Armstrong [this message]
2020-07-02 18:03 ` Daniel Vetter
2020-07-02 7:47 ` [PATCH v8 2/6] drm/meson: add Amlogic Video FBC registers Neil Armstrong
2020-07-02 7:47 ` [PATCH v8 3/6] drm/meson: overlay: setup overlay for Amlogic FBC Neil Armstrong
2020-07-02 7:47 ` [PATCH v8 4/6] drm/meson: overlay: setup overlay for Amlogic FBC Memory Saving mode Neil Armstrong
2020-07-02 7:47 ` [PATCH v8 5/6] drm/meson: overlay: setup overlay for Amlogic FBC Scatter Memory layout Neil Armstrong
2020-07-02 7:47 ` [PATCH v8 6/6] drm/meson: crtc: handle commit of Amlogic FBC frames Neil Armstrong
2020-07-02 18:57 ` [PATCH v8 0/6] drm/meson: add support for Amlogic Video FBC Kevin Hilman
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