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Date: Wed, 2 Jan 2013 07:41:50 +0200 From: Terje Bergström <tbergstrom@...dia.com> To: Stephen Warren <swarren@...dotorg.org> CC: Arto Merilainen <amerilainen@...dia.com>, Thierry Reding <thierry.reding@...onic-design.de>, "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>, "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: Re: [RFC v2 6/8] gpu: drm: tegra: Remove redundant host1x On 21.12.2012 23:19, Stephen Warren wrote: > * There's host1x hardware. > > * There's a low-level driver just for host1x itself; the host1x driver. > > * There's a high-level driver for the entire host1x complex of devices. > That is tegradrm. There may be more high-level drivers in the future > (e.g. v4l2 camera driver if it needs to aggregate a bunch of host1x > sub-devices liek tegradrm does). tegradrm is a driver for a couple of the host1x clients, namely DC and HDMI, and now adding 2D. > * The presence of the host1x DT node logically implies that both the two > drivers in the previous two points should be instantiated. > > * Linux instantiates a single device per DT node. > > * So, it's host1x's responsibility to instantiate the other device(s). I > think it's reasonable for the host1x driver to know exactly what > features the host1x HW complex supports; raw host1x access being one, > and the higher level concept of a tegradrm being another. So, it's > reasonable for host1x to trigger the instantiation of tegradrm. tegradrm has drivers for each device that it controls, so tegradrm via kernel device-driver model instantiates them. host1x driver doesn't need to do that. > * If DRM core didn't stomp on the device object's drvdata (or whichever > field it is), I would recommend not creating a dummy device at all, but > rather having the host1x driver directly implement multiple driver > interfaces. There are many examples like this already in the kernel, > e.g. combined GPIO+IRQ driver, combined GPIO+IRQ+pinctrl driver, etc. This is the architecture that would imply host1x instantiating everything, and DRM being a subcomponent of host1x driver. But we didn't choose to go there. We agreed to have tegradrm and host1x drivers separate. Terje -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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