Hi all, I'm attempting to write a platform device driver that gets loaded when a compatible device-tree overlay is loaded by dtoverlay. This is just a learning exercise at the moment, so I'm trying to write the simplest platform device I can, rather than extending one of the device drivers that extend platform device (terminology?). I'm trying to get just enough to get the driver's probe() function called when the device-tree overlay is applied, and then create a misc device. My module seems to init just fine, and the device-tree overlay seems to also load without issue, but for some reason probe() is never called. Am I correct in using probe() with platform devices? I understand platform devices can't be enumerated/detected, but I thought that probe() would be called when there was a compatibility match between the driver and the device-tree overlay. Any pointers would be much appreciated. Cheers, Laurence. Here's what /sys shows: $ cat /sys/devices/platform/gde060f3/uevent OF_NAME=gde060f3 OF_FULLNAME=/gde060f3 OF_COMPATIBLE_0=gde060f3 OF_COMPATIBLE_N=1 MODALIAS=of:Ngde060f3T<NULL>Cgde060f3 $ cat /sys/firmware/devicetree/base/gde060f3/compatible gde060f3 $ cat /sys/firmware/devicetree/base/gde060f3/name gde060f3 $ cat /sys/firmware/devicetree/base/gde060f3/status okay Here's the loaded device-tree: $ dtc -I fs /proc/device-tree /dts-v1/; / { compatible = "raspberrypi,3-model-b-plus", "brcm,bcm2837"; serial-number = "00000000427625f0"; model = "Raspberry Pi 3 Model B Plus Rev 1.3"; memreserve = <0x3b400000 0x4c00000>; interrupt-parent = <0x1>; #address-cells = <0x1>; #size-cells = <0x1>; clocks { *** SNIPPED *** }; __overrides__ { *** SNIPPED *** }; gde060f3 { compatible = "gde060f3"; status = "okay"; phandle = <0x7b>; linux,phandle = <0x7b>; }; system { linux,serial = <0x0 0x427625f0>; linux,revision = <0xa020d3>; }; *** SNIPPED *** }; module file: #define DEBUG #include <linux/kernel.h> #include <linux/module.h> #include <linux/platform_device.h> #include <linux/miscdevice.h> #include <linux/fs.h> #include <linux/uaccess.h> #include <linux/slab.h> struct gde060f3_struct { struct platform_device *pdev; struct miscdevice mdev; }; static inline struct gde060f3_struct *to_gde060f3_struct(struct file *file) { struct miscdevice *miscdev = file->private_data; return container_of(miscdev, struct gde060f3_struct, mdev); } static ssize_t gde060f3_read(struct file *file, char __user *buf, size_t count, loff_t *pos) { struct gde060f3_struct *gde060f3 = to_gde060f3_struct(file); /* just for example */ (void)gde060f3; /* unused */ return simple_read_from_buffer(buf, count, pos, "gde060f3 text", 14); } static const struct file_operations gde060f3_fops = { .owner = THIS_MODULE, .read = gde060f3_read, }; static const struct of_device_id gde060f3_match[] = { { .compatible = "gde060f3" }, {}, }; MODULE_DEVICE_TABLE(of, gde060f3_match); static int gde060f3_probe(struct platform_device *pdev) { struct gde060f3_struct *gde060f3; int ret; pr_info("gde060f3_probe()\n"); gde060f3 = kmalloc(sizeof(*gde060f3), GFP_KERNEL); if (!gde060f3) return -ENOMEM; platform_set_drvdata(pdev, gde060f3); gde060f3->pdev = pdev; gde060f3->mdev.minor = MISC_DYNAMIC_MINOR; gde060f3->mdev.name = "gde060f3"; gde060f3->mdev.fops = &gde060f3_fops; gde060f3->mdev.parent = NULL; ret = misc_register(&gde060f3->mdev); if (ret) { dev_err(&pdev->dev, "Failed to register miscdev\n"); return ret; } dev_info(&pdev->dev, "Registered\n"); pr_info("Registered\n"); return 0; } static int gde060f3_remove(struct platform_device *pdev) { struct gde060f3_struct *gde060f3 = platform_get_drvdata(pdev); misc_deregister(&gde060f3->mdev); kfree(gde060f3); dev_info(&pdev->dev, "Unregistered\n"); pr_info("Unregistered\n"); return 0; } static struct platform_driver gde060f3_driver = { .probe = gde060f3_probe, .remove = gde060f3_remove, .driver = { .name = "gde060f3", .of_match_table = gde060f3_match, }, }; module_platform_driver_probe(gde060f3_driver, gde060f3_probe); MODULE_AUTHOR("Laurence Rochfort <laurence.rochfort@gmail.com>"); MODULE_DESCRIPTION("GPIO driver for Good Display GDE060F3 ePaper Display"); MODULE_LICENSE("GPL"); overlay file: /dts-v1/; /plugin/; / { compatible = "brcm,bcm2708"; fragment@0 { // target or target-path? target-path = "/"; __overlay__ { gde060f3: gde060f3 { compatible = "gde060f3"; status = "okay"; }; }; }; };