From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: Rob Herring <robh@kernel.org>, Daniel Vetter <daniel@ffwll.ch>
Cc: devicetree@vger.kernel.org,
Maxime Ripard <maxime.ripard@bootlin.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
David Airlie <airlied@linux.ie>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Sean Paul <sean@poorly.run>
Subject: Re: [PATCH] drm: support gpu aliases defined in DT data
Date: Fri, 18 Jan 2019 10:29:33 +0200 [thread overview]
Message-ID: <e5513293-416c-f4aa-a6ab-7c4e762753ed@ti.com> (raw)
In-Reply-To: <CAL_JsqLRPyxX2WDo-87mvXSC-SKTEnF6rR8OA1wd0hs-w4ohdw@mail.gmail.com>
On 18/01/19 00:04, Rob Herring wrote:
> Mesa/libdrm already has lots of code to open the correct devices and
> not care about minor numbers. What's the problem here?
Well, maybe the problem is that I don't know how to do this =).
So, if we have multiple DRM devices, how does one manage those?
Iterating over them and looking for kms-capable ones is easy enough. But
if there are multiple kms-capable ones, how should the userspace choose
between those?
I see that udev creates /dev/dri/by-path/ links to the cards, should the
userspace use those to have a persistent link to the card? E.g. first
time the app is ran, it'll collect all the kms-capable cards, and store
the by-path names somewhere, and in subsequent runs it will instead use
the by-path names to keep the order the same.
If I have a product with two display controllers, and one of them has
the main display connected, how does my custom app know which card to
use? Hardcoding the by-path in the app?
If udev/systemd is not available, how does the userspace do this? I
tried to see if one can get enough information from the card device with
ioctls to figure these things out, but I didn't figure this out. Should
the drmGetBusid() return something for platform devices too? Maybe I've
got something missing from the display driver, and drmGetBusid() should
return something similar as what is in the by-path name.
Tomi
--
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next prev parent reply other threads:[~2019-01-18 8:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-17 11:19 [PATCH] drm: support gpu aliases defined in DT data Tomi Valkeinen
2019-01-17 11:35 ` Maxime Ripard
2019-01-17 12:33 ` Daniel Vetter
2019-01-17 13:04 ` Tomi Valkeinen
2019-01-17 13:26 ` Daniel Vetter
2019-01-17 13:56 ` Tomi Valkeinen
2019-01-17 22:04 ` Rob Herring
2019-01-18 8:29 ` Tomi Valkeinen [this message]
2019-03-06 1:41 ` Laurent Pinchart
2019-03-06 7:49 ` Tomi Valkeinen
2019-04-17 17:42 ` Emil Velikov
2019-04-26 11:23 ` Tomi Valkeinen
2019-01-17 21:38 ` Eric Anholt
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