devm_ioremap_resource() creates duplicate resource

devm_ioremap_resource() creates duplicate resource

[Pavel Roskin]

Hello!

I'm writing a device driver for a subdevice of a PCIe multifunctional
device. It's a platform device that has its resources described in the
top-level driver for the multifuctional device.

I followed the common pattern when a memory resource is obtained by
calling platform_get_resource() and then reserved and remapped by
calling devm_ioremap_resource().

  res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  base = devm_ioremap_resource(&pdev->dev, res);

The problem with that approach is that the resource appears twice in
/proc/iomem:

  fdc60000-fdc6000f : My Dev
    fdc60000-fdc6000f : My Dev

I see that devm_ioremap_resource() takes the start address and the
size of the existing resource and reserves the region at the same
address.

Some drivers (e.g. drivers/mfd/db8500-prcmu.c) use devm_ioremap()
instead. But my concern is that the resource is not marked as busy in
that case.

Which approach is preferred? If there a good way to mark an existing
resource as busy (short of direct flag manipulation)? Would it make
sense to have an API to reserve an existing resource?

-- 
Regards,
Pavel Roskin

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