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
