Multiple issues with omapdrm

[Tomi Valkeinen]

On 05/06/13 14:52, Rob Clark wrote:
> On Wed, Jun 5, 2013 at 7:35 AM, Tomi Valkeinen <tomi.valkeinen at ti.com> wrote:
>> On 05/06/13 13:57, Rob Clark wrote:
>>
>>> 1) drmOpen("omap") will try to modprobe "omap", not "omapdrm" so we
>>> need to rename the .ko
>>
>> Has something been changed that broke that? Or was "omapdrm" just a
>> badly chosen name from the start? If drmOpen("omapdrm") works now,
>> doesn't changing the module name break userspace compatibility?
> 
> it was broken all along, because you need to drmOpen("omap") so the
> module should have been called omap.ko from the beginning

But it wasn't, so wouldn't changing it break userspace compatibility?

Why do you "need" drmOpen("omap")? Is it just a convention to use that
kind of name, instead of "omapdrm" style name?

>> I had a quick look at libdrm. It calls server_info->load_module() but I
>> couldn't figure out where that call actually goes...
> 
> it's registered from xserver, fyi

Ah ok. So in my testing, running without X, there's actually no module
loading happening. The test tools print something like "trying to load
module omapdrm...success." but I guess that only means that the module
is already there.

>>> 2) sorting out the modprobe of panel drivers..  although with the
>>> current structure of omapdrm+omapdss I can't think of any clean way to
>>> handle this.  I suppose we could do a hack with a bunch of
>>> request_module()s
>>
>> If omapdrm and omapdss were merged, what would be the clean way be? Or
>> did you mean some other structure?
> 
> well, then we'd just build it all into one .ko

So you didn't actually mean omapdrm+omapdss, but omapdrm + omapdss +
all-the-panel-drivers? And then have some kind of forced method to probe
the panels at omapdrm start?

That would be quite a horrible solution, in my opinion =). It would also
be even worse when we get platform independent panel drivers, as all the
drm drivers using those panel drivers would include all the panel drivers.

>> I'm no expert on this, but my understanding is that udev (or such)
>> should load the modules for the devices that the board has. If it's a
>> requirement that the drm drivers are loaded only by a call to drmOpen()
>> (why is that?), then maybe udev could load only the panel drivers.
> 
> I'm not quite sure the entire history offhand.. maybe drmOpen()
> pre-dated that?  At any rate, the main issue is just ensuring the
> panel modules (if they are split out into different .ko's) are loaded
> first

I think there should be a core display facility in the kernel to which
the panel drivers register the displays in probe().

At boot time udev would go through /sys, find the panel devices somehow
(how? modalias is probably somehow involved..), and load their
respective modules.

Later, when X is started, omapdrm and omapdss are loaded, and at that
point all the panels are already there.

 Tomi


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