Re: [PATCH] serial: 8250: Add support for using platform_device resources

[Andy Shevchenko]

On Tue, May 14, 2019 at 10:24 AM Esben Haabendal <esben@xxxxxxxxxxxx> wrote:
> Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> writes:
> > On Tue, May 07, 2019 at 02:22:18PM +0200, Esben Haabendal wrote:

> We are on repeat here.  I don't agree with you here.  I have a simple
> generic 8250 (16550A) compatible device, and cannot use it in a mfd
> driver using the standard mfd-core framework.

> The lacking of support for platform_get_resource() in the generic
> serial8250 driver is not a feature.  It should be supported, just as it
> is in several of the specialized 8250 drivers.

We are going circles here.
What exactly prevents you to use it? Presence of request_mem_region()?

> It would still mean that I would have revert to not using convenient and
> otherwise fully appropriate API calls like pci_request_regions() and
> mfd_add_devices().

Yes, here is the issue. 8250 requires the parent not to *request*
resources. Because child handles IO access itself.

> The mfd driver in question is for a PCI device.  Not being able to
> request the PCI regions seems silly.

Nope. Otherwise, the parent which *doesn't handle* IO on behalf of
child should not request its resources.

> Not being able to register all child devices with the call introduced
> for that sole purpose also seems silly.

> Please take a look at https://lkml.org/lkml/2019/4/9/576
> ("[PATCH v2 2/4] mfd: ioc3: Add driver for SGI IOC3 chip")

Thank you for this link.
Now, look at this comment:

+ /*
+ * Map all IOC3 registers.  These are shared between subdevices
+ * so the main IOC3 module manages them.
+ */

Is it your case? Can we see the code?

-- 
With Best Regards,
Andy Shevchenko