Archit Taneja writes: > On 06/28/2017 01:28 AM, Eric Anholt wrote: >> When a mipi_dsi_host is registered, the DT is walked to find any child >> nodes with compatible strings. Those get registered as DSI devices, >> and most DSI panel drivers are mipi_dsi_drivers that attach to those nodes. >> >> There is one special case currently, the adv7533 bridge, where the >> bridge probes on I2C, and during the bridge attach step it looks up >> the mipi_dsi_host and registers the mipi_dsi_device (for its own stub >> mipi_dsi_driver). >> >> For the Raspberry Pi panel, though, we also need to attach on I2C (our >> control bus), but don't have a bridge driver. The lack of a bridge's >> attach() step like adv7533 uses means that we aren't able to delay the >> mipi_dsi_device creation until the mipi_dsi_host is present. >> >> To fix this, we extend mipi_dsi_device_register_full() to allow being >> called with a NULL host, which puts the device on a queue waiting for >> a host to appear. When a new host is registered, we fill in the host >> value and finish the device creation process. > > This is quite a nice idea. The only bothering thing is the info.of_node usage > varies between child nodes (mipi_dsi_devs) and non-child nodes (i2c control > bus). > > For DSI children expressed in DT, the of_node in info holds the DT node > corresponding to the DSI child itself. For non-DT ones, this patch assumes > that info.of_node stores the DSI host DT node. I think it should be okay as > long as we mention the usage in a comment somewhere. The other option is to > have a new info.host_node field to keep a track of the host DT node. I think maybe you misread the patch? We're using of_get_parent(dsi->dev.node), which came from info->node, to compare to host->dev->of_node().