Device Tree Child Node Parsing Question

Hi,

What is the best way to queue devicetree child nodes so the node is passed in the platform_device pointer to the probe() function?

Documentation/devicetree/usage-model.txt has the following:

"For Linux DT support, the generic behaviour is for child devices to be registered by the parent's device driver at driver .probe() time."

"Actually, it turns out that registering children of some platform_devices as more platform_devices is a common pattern, and the
device tree support code reflects that and makes the above example simpler. The second argument to of_platform_populate() is an of_device_id table, and any node that matches an entry in that table will also get its child nodes registered."

I tried calling of_platform_populate() in the probe of the a10_sysctl node but it doesn't appear to setup the platform device data properly for the sub-child nodes.

The top child node (a10_sysctl) is probed properly and has a valid of_node passed in. However, the sub-child nodes such as gpio4 have null passed in for pdev->dev.of_node (gpio4 probe prototype is int a10sycon_gpio_probe(struct platform_device *pdev).

My current solution is to call of_find_matching_node() in a10sycon_gpio_probe() to get a valid node pointer but other examples tend to dereference pdev->dev.of_node.

Thank you in advance for your insight.

Thor

My device tree looks like this:

/ {
    soc {
        spi0: spi@fff00000 {
             compatible = "snps,dw-spi-mmio";
             #address-cells = <1>;
             #size-cells = <0>;
             reg = <0xfff00000 0x1000>;
             interrupts = <0 154 4>;
             num-chipselect = <4>;
             clocks = <&per_base_clk>;
             status = "okay";

             a10_sysctl: a10_sysctl@0 {
                compatible = "altr,a10sycon";
                reg = <0>;
                interrupt-parent = <&gpio2>;
                /* low-level active IRQ at GPIO2_24 */
                interrupts = <24 0x8>;
                interrupt-controller;
                #interrupt-cells = <2>;
                spi-max-frequency = <100000>;

                gpio4: gpio-controller {
                        compatible = "altr,a10sycon-gpio";
                        gpio-controller;
                        #gpio-cells = <2>;
                        ngpios = <16>;

                };

                a10rst: a10rst {
                        compatible = "altr,a10sycon-reset";
                        #reset-cells = <1>;
                };
            };
        };

Quoted 22 lines · Thor Thayer

Hi,

What is the best way to queue devicetree child nodes so the node is passed in the platform_device pointer to the probe() function?

Documentation/devicetree/usage-model.txt has the following:

"For Linux DT support, the generic behaviour is for child devices to be registered by the parent's device driver at driver .probe() time."

"Actually, it turns out that registering children of some platform_devices as more platform_devices is a common pattern, and the
device tree support code reflects that and makes the above example simpler. The second argument to of_platform_populate() is an of_device_id table, and any node that matches an entry in that table will also get its child nodes registered."

I tried calling of_platform_populate() in the probe of the a10_sysctl node but it doesn't appear to setup the platform device data properly for the sub-child nodes.

This should work. There are quite a few users already including unit tests. Can you tell what you are doing differently from those users?

Rob

Quoted 1 line

Hi,

What is the best way to queue devicetree child nodes so the node is passed in the platform_device pointer to the probe() function?

Documentation/devicetree/usage-model.txt has the following:

"For Linux DT support, the generic behaviour is for child devices to be registered by the parent's device driver at driver .probe() time."

"Actually, it turns out that registering children of some platform_devices as more platform_devices is a common pattern, and the device tree support code reflects that and makes the above example
simpler. The second argument to of_platform_populate() is an
of_device_id table, and any node that matches an entry in that table
will also get its child nodes registered."

I tried calling of_platform_populate() in the probe of the a10_sysctl node but it doesn't appear to setup the platform device data properly for the sub-child nodes.

The top child node (a10_sysctl) is probed properly and has a valid of_node passed in. However, the sub-child nodes such as gpio4 have null passed in for pdev->dev.of_node (gpio4 probe prototype is int a10sycon_gpio_probe(struct platform_device *pdev).

My current solution is to call of_find_matching_node() in a10sycon_gpio_probe() to get a valid node pointer but other examples tend to dereference pdev->dev.of_node.

Thank you in advance for your insight.

Thor

My device tree looks like this:

/ {
     soc {
         spi0: spi@fff00000 {
          compatible = "snps,dw-spi-mmio";
          #address-cells = <1>;
          #size-cells = <0>;
          reg = <0xfff00000 0x1000>;
          interrupts = <0 154 4>;
          num-chipselect = <4>;
          clocks = <&per_base_clk>;
          status = "okay";

              a10_sysctl: a10_sysctl@0 {
         compatible = "altr,a10sycon";
         reg = <0>;
         interrupt-parent = <&gpio2>;
         /* low-level active IRQ at GPIO2_24 */
         interrupts = <24 0x8>;
         interrupt-controller;
         #interrupt-cells = <2>;
         spi-max-frequency = <100000>;

         gpio4: gpio-controller {
             compatible = "altr,a10sycon-gpio";
             gpio-controller;
             #gpio-cells = <2>;
             ngpios = <16>;
         };

         a10rst: a10rst {
             compatible = "altr,a10sycon-reset";
             #reset-cells = <1>;
         };
         };
     };

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