On Thu, 24 Dec 2015 10:52:07 +0000
Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote:
> On Thu, Dec 24, 2015 at 09:15:28AM +0100, Jean-Francois Moine wrote:
> > Well, two topics:
> >
> > - adding a second 'of_compare' function complexifies the code
> > and people may wonder why such a function is needed and what
> > they have to put inside.
> >
> > - usually, the component drivers just do a component_add() of the device
> > at probe time.
>
> ... which is exactly what does happen throughout imx-drm.
>
> > Now, as the bind() function of the components of the first level
> > returns the port in 'data', some work has to be done for retrieving
> > the device.
> > This can (should?) be done in the bind() function.
>
> Sorry, this still makes zero sense to me. "retrieving the device"
> is all done by the core component code and has nothing to do with
> the drivers themselves.
Right, sorry, I wrote 'data' while thinking 'dev'.
> > In drm/imx/ipuv3-crtc.c, this is done by a hack, changing the device
> > node reference before calling component_add()!
>
> What hack?
[snip]
> There's no hack there. I see nothing changing dev->of_node there.
Right again, I was looking in 4.4-rc1.
> > I looked at the imx-drm and the associated DTs, and I think that,
> > without the v2 patch and keeping the port parent as the component
> > (previous mail), the code could be simplified adding an intermediate
> > device node in the DT.
>
> Not going to happen, because that's going to break compatibility with
> existing DTs.
OK, I cannot discuss against that!
> Let me explain instead what's going on, and why imx-drm is different.
Already understood.
[snip]
> However, when we come to the Linux implementation, things get sticky
> because we need to select the correct platform device corresponding
> with the IPU's port. This can only be done using the 'port' node
> and not port->parent.
>
> port->parent would be the IPU device node itself. If we were to
> introduce the additional ports {} node, that doesn't help, because
> now port->parent points at the ports {} node instead, not the actual
> port - and we need the port itself to identify which of the IPU's
> own created platform devices to select.
>
> So, modifying DT doesn't help in any way, even if you ignore the fact
> that we need to maintain backwards compatibility.
The ports {} node is just a container, and so is the (unique) port {}
node which is inside:
ipu1: ipu@02400000 {
...
ports@2 { /* di0 device */
ipu1_di0: port {
...
ipu1_di0_hdmi: endpoint@1 {
remote-endpoint = <&hdmi_mux_0>;
};
ipu1_di0_mipi: endpoint@2 {
remote-endpoint = <&mipi_mux_0>;
};
...
};
};
ports@3 { /* di1 device */
ipu1_di1: port {
...
ipu1_di1_hdmi: endpoint@1 {
remote-endpoint = <&hdmi_mux_1>;
};
ipu1_di1_mipi: endpoint@2 {
remote-endpoint = <&mipi_mux_1>;
};
...
};
};
};
--
Ken ar c'hentañ | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/
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