On Sun, Feb 10, 2013 at 10:37 AM, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Sun, Feb 10, 2013 at 02:49:21AM +0100, Javier Martinez Canillas wrote: >> I knew this would be controversial and that's why I didn't mean it to be a patch >> but a RFC :) >> >> The problem basically is that you have to associate the platform device with its >> corresponding DT device node because it can be used in the driver probe function. > > When DT is being used, doesn't DT create the platform devices for you, > with the device node already set correctly? > Well they usually do but not always just like usually you have a platform_device in your board code and call platform_device_register(). But in some configurations you can't just define the platform_device required resources (I/O memory, IRQ, etc) as static platform data. In some cases you need a level of indirection. In this particular case a SMSC ethernet chip is connected to an OMAP3 processor through its General-Purpose Memory Controller. You can't just define the I/O memory used by the device since you first need to request that address to the GPMC. The same happens with the IRQ line since a OMAP GPIO pin is used so you have to first configure the GPIO line as input. So in platform code you call to gpmc_smsc911x_init() passing all the GPMC specific configurations (GPIO used for IRQ, GPMC chip select, etc) Then gpmc_smsc911x_init() does all the needed setup, fills a platform_data for the real platform_device and calls platform_device_register_resndata(). >From the smsc911x platform_driver probe function point of view it just have resources and doesn't know if it's I/O memory is directly mapped or is through a memory controller as the GPMC. It also doesn't know if the IRQ is a GPIO or not. Another approach could be extending the current SMSC LAN DT binding with GPMC-specific properties so the platform driver could do this setup when the device node is found and the probe function is called. > Manually creating platform devices and adding DT nodes to it sounds like > the wrong thing to be doing. > -- Yes, I don't like this approach to much either but I didn't find a better way to do it. That was the main point of this RFC. I'm still learning about Device Trees so I hope that someone with more experience with DT or more familiarized with OMAP GPMC and the SMSC driver could take a step forward and help me giving a better idea. Thanks a lot for your feedback and best regards, Javier -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
