Revert "mfd: cros_ec: Use devm_kzalloc for private data"

This reverts commit 3aa2177e.

That commit triggered a new WARN when unloading the module (see at the
end of the commit message). When a class_dev is embedded in a structure
then that class_dev is the thing that controls the lifetime of that
structure, for that reason device managed allocations can't be used here.
See Documentation/kobject.txt.

Revert the above patch, so the struct is allocated using kzalloc and we
have a release function for it that frees the allocated memory, otherwise
it is broken.

 ------------[ cut here ]------------
 Device 'cros_ec' does not have a release() function, it is broken and must be fixed.
 WARNING: CPU: 3 PID: 3675 at drivers/base/core.c:895 device_release+0x80/0x90
 Modules linked in: btusb btrtl btintel btbcm bluetooth ...
 CPU: 3 PID: 3675 Comm: rmmod Not tainted 4.20.0-rc4 #76
 Hardware name: Google Kevin (DT)
 pstate: 40000005 (nZcv daif -PAN -UAO)
 pc : device_release+0x80/0x90
 lr : device_release+0x80/0x90
 sp : ffff00000c47bc70
 x29: ffff00000c47bc70 x28: ffff8000e86b0d40
 x27: 0000000000000000 x26: 0000000000000000
 x25: 0000000056000000 x24: 0000000000000015
 x23: ffff8000f0bbf860 x22: ffff000000d320a0
 x21: ffff8000ee93e100 x20: ffff8000ed931428
 x19: ffff8000ed931418 x18: 0000000000000020
 x17: 0000000000000000 x16: 0000000000000000
 x15: 0000000000000400 x14: 0000000000000143
 x13: 0000000000000000 x12: 0000000000000400
 x11: 0000000000000157 x10: 0000000000000960
 x9 : ffff00000c47b9b0 x8 : ffff8000e86b1700
 x7 : 0000000000000000 x6 : ffff8000f7d520b8
 x5 : ffff8000f7d520b8 x4 : 0000000000000000
 x3 : ffff8000f7d58e68 x2 : ffff8000e86b0d40
 x1 : 37d859939c964800 x0 : 0000000000000000
 Call trace:
  device_release+0x80/0x90
  kobject_put+0x74/0xe8
  device_unregister+0x20/0x30
  ec_device_remove+0x34/0x48 [cros_ec_dev]
  platform_drv_remove+0x28/0x48
  device_release_driver_internal+0x1a8/0x240
  driver_detach+0x40/0x80
  bus_remove_driver+0x54/0xa8
  driver_unregister+0x2c/0x58
  platform_driver_unregister+0x10/0x18
  cros_ec_dev_exit+0x1c/0x2d8 [cros_ec_dev]
  __arm64_sys_delete_module+0x16c/0x1f8
  el0_svc_common+0x84/0xd8
  el0_svc_handler+0x2c/0x80
  el0_svc+0x8/0xc
 ---[ end trace a57c4625f3c60ae8 ]---

Cc: stable@vger.kernel.org
Fixes: 3aa2177e ("mfd: cros_ec: Use devm_kzalloc for private data")
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Reviewed-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/cros_ec_dev.c

@@ -263,6 +263,11 @@ static const struct file_operations fops = {
 #endif
 };
 
+static void cros_ec_class_release(struct device *dev)
+{
+	kfree(to_cros_ec_dev(dev));
+}
+
 static void cros_ec_sensors_register(struct cros_ec_dev *ec)
 {
 	/*
@@ -395,7 +400,7 @@ static int ec_device_probe(struct platform_device *pdev)
 	int retval = -ENOMEM;
 	struct device *dev = &pdev->dev;
 	struct cros_ec_platform *ec_platform = dev_get_platdata(dev);
-	struct cros_ec_dev *ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
+	struct cros_ec_dev *ec = kzalloc(sizeof(*ec), GFP_KERNEL);
 
 	if (!ec)
 		return retval;
@@ -417,6 +422,7 @@ static int ec_device_probe(struct platform_device *pdev)
 	ec->class_dev.devt = MKDEV(ec_major, pdev->id);
 	ec->class_dev.class = &cros_class;
 	ec->class_dev.parent = dev;
+	ec->class_dev.release = cros_ec_class_release;
 
 	retval = dev_set_name(&ec->class_dev, "%s", ec_platform->ec_name);
 	if (retval) {