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From: Daniel Stone <daniel@fooishbar.org>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: nd <nd@arm.com>, Neil Armstrong <narmstrong@baylibre.com>,
	"khilman@baylibre.com" <khilman@baylibre.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-amlogic@lists.infradead.org"
	<linux-amlogic@lists.infradead.org>,
	Ayan Halder <Ayan.Halder@arm.com>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 4/7] drm/meson: plane: add support for AFBC mode for OSD1 plane
Date: Fri, 11 Oct 2019 08:56:26 +0100
Message-ID: <CAPj87rOMupGnq5B=eWjcu0-Bkj_HmfLDR3Aqk1VDCXg8TwYP0w@mail.gmail.com> (raw)
In-Reply-To: <CAKMK7uE2p_VbJB5PfS1DJ5AzOm60p22c+YOJ18FtD4_ec61LwQ@mail.gmail.com>

Hi,

On Fri, 11 Oct 2019 at 08:46, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Thu, Oct 10, 2019 at 7:32 PM Ayan Halder <Ayan.Halder@arm.com> wrote:
> > On Thu, Oct 10, 2019 at 03:41:15PM +0200, Neil Armstrong wrote:
> > > Sorry I don't understand, you ask me to limit AFBC to ABGR8888 ?
> >
> > Apologies for the confusion, as per the link, the formats which are
> > suggested with AFBC_FORMAT_MOD_YTR are the BGR/ABGR formats (as
> > listed in the 'AFBC formats' table)
> >
> > Thus, any other permutation of the components might make it incompatible
> > with some other AFBC producers/consumers.
>
> Uh, that's not how this is supposed to be used. Drivers are meant to
> expose _everything_ they support (bonus if you roughly sort it in
> preference order). Userspace then computes the intersection of
> modifiers/formats supported by all devices it needs to share a buffer
> with. Allowing that was the entire point of modifiers, if we
> artificially limit to the common denominator we're back "only linear
> works everywhere".

Correct.

A lot of userspace will select for format first, then find a modifier
which can be used with that format. If userspace has specific
knowledge of AFBC and decides that it prefers to use AFBC so will seek
out an alpha format - and make sure everyone fills the channel solid -
then that's fine. But that's putting the cart before the horse.

Not exposing XRGB8888 on the primary plane will break a lot of
userspace, so in this case AFBC would just never really be used.

Cheers,
Daniel

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Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-10  9:25 [PATCH 0/7] drm/meson: add AFBC support Neil Armstrong
2019-10-10  9:25 ` [PATCH 1/7] drm/meson: add AFBC decoder registers for GXM and G12A Neil Armstrong
2019-10-10  9:25 ` [PATCH 2/7] drm/meson: store the framebuffer width for plane commit Neil Armstrong
2019-10-10  9:25 ` [PATCH 3/7] drm/meson: Add AFBCD module driver Neil Armstrong
2019-10-10  9:25 ` [PATCH 4/7] drm/meson: plane: add support for AFBC mode for OSD1 plane Neil Armstrong
2019-10-10 13:26   ` Ayan Halder
2019-10-10 13:41     ` Neil Armstrong
2019-10-10 17:31       ` Ayan Halder
2019-10-11  7:46         ` Daniel Vetter
2019-10-11  7:56           ` Daniel Stone [this message]
2019-10-11  8:41       ` Brian Starkey
2019-10-11  9:14         ` Neil Armstrong
2019-10-11 10:56           ` Brian Starkey
2019-10-11 12:07             ` Neil Armstrong
2019-10-15 11:18               ` Brian Starkey
2019-10-15 11:46                 ` Neil Armstrong
2019-10-11 17:25             ` Daniel Vetter
2019-10-14  9:11               ` Brian Starkey
2019-10-14  9:20                 ` Daniel Vetter
2019-10-10  9:25 ` [PATCH 5/7] drm/meson: viu: add AFBC modules routing functions Neil Armstrong
2019-10-10  9:25 ` [PATCH 6/7] drm/meson: hold 32 lines after vsync to give time for AFBC start Neil Armstrong
2019-10-10  9:25 ` [PATCH 7/7] drm/meson: crtc: add OSD1 plane AFBC commit Neil Armstrong

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