Re: [PATCH 0/3] drm/exynos: Allow module to be autoloaded

[Sjoerd Simons <sjoerd.simons@collabora.co.uk>]

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Hey Inki,

On Mon, 2014-07-21 at 12:02 +0900, Inki Dae wrote:
> On 2014년 07월 19일 05:36, Sjoerd Simons wrote:
> > The exynos DRM module currently is not automatically loaded when build as a
> > module. This is due to the simple fact that it doesn't have any
> > MODULE_DEVICE_TABLE entries whatsoever... Most of these were removed previously
> > as it wasn't possible at the time to have multiple calls to MODULE_DEVICE_TABLE
> > in one module, however commit 21bdd17b21b45ea solved that.
> > 
> > The first two patches revert the previous removals of MODULE_DEVICE_TABLE
> > calls, while the last one adds calls for the remaining OF match tables without a
> > MODULE_DEVICE_TABLE call.

> Exynos drm follows single-driver model. So each usb driver of Exynos drm
> wouldn't need its own MODULE_DEVICE_TABLE.

Strictly speaking you're right, for module autoloading to work the
module just needs to have one that matches. So in principle all other
entries are redundant.

However for exynos drm there does not seem to be one main device which
is guaranteed to always be present which can be used to key the module
autoloading of. So you still need seperate MODULE_DEVICE_TABLE entries
for all the various subdrivers to ensure autoloading actually happens,
especially since the various subdrivers can be seperately enabled
at build time. 

The one exception from the above might be the HDMI sub-driver, which is
always build together with the mixer (And i asume the HDMI hw block
depends on the mixer block for its input). However it seems more elegant
and less error-prone to have simply entries for both, rather then
implicitly replying on the other (sub)driver to trigger module loading.
Especially given there is essentially no cost in having another module
alias.

-- 
Sjoerd Simons <sjoerd.simons@collabora.co.uk>
Collabora Ltd.

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