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