On 02/02/2014 07:23 PM, Russell King - ARM Linux wrote:
On Sun, Feb 02, 2014 at 07:06:06PM +0100, Jean-Francois Moine wrote:
- on encoder_destroy(), the function drm_i2c_encoder_destroy()
unregisters the i2c client, so, with a DT, a second encoder_init()
would crash.
I think this is one of the down-sides of trying to bolt DT into this:
the drm encoder slave support is not designed to cope with an i2c client
device pre-created.
In fact, I can't see how this stuff comes anywhere close to working in
a DT setup: in such a scenario, you declare that there's a tda998x
device in DT. I2C parses this, and creates an i2c_client itself for
the tda998x.
When the TDA998x driver initialises, it finds this i2c client and
binds to it, calling tda998x_probe(), which does nothing.
However, the only way to attach a slave encoder to a DRM device is via
a call to drm_i2c_encoder_init(), which unconditionally calls
i2c_new_device(). This creates a _new_ i2c_client structure, again
unconditionally, for the tda998x. This must be bound by the I2C
subsystem to a driver - hopefully the tda998x driver, which then
calls it's encoder_init function.
None of this will happen if DT has already created an i2c_client at
the appropriate address, because DRMs i2c_new_device() will fail.
drm_i2c_encoder_init() could look at .of_node of the i2c_board_info.
If it is there, do not try to i2c_new_device as it has already been
registered by DT i2c auto-probing.
Sebastian
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