linux-kernel - RE: [PATCH v9 5/7] ACPI: Translate the I/O range of non-MMIO devices before scanning

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Date:   Tue, 4 Jul 2017 15:14:42 +0000
From:   Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "frowand.list@...il.com" <frowand.list@...il.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "brian.starkey@....com" <brian.starkey@....com>,
        "olof@...om.net" <olof@...om.net>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "minyard@....org" <minyard@....org>,
        John Garry <john.garry@...wei.com>,
        "xuwei (O)" <xuwei5@...ilicon.com>
Subject: RE: [PATCH v9 5/7] ACPI: Translate the I/O range of non-MMIO
 devices before scanning

Hi Andy

[...]

> 
> JFYI: Mika on vacation.

Thanks for letting me know

> 
> > I had a look into the MFD framework. If my understanding is correct
> the mfd
> > framework create a platform device for each declared mfd_cell that is
> passed
> > to mfd_add_devices().
> 
> Right.
> 
> > However there is something that I do not quite understand:
> > from
> > http://elixir.free-electrons.com/linux/latest/source/drivers/mfd/mfd-
> core.c#L207
> > it seems that mfd_add_device() will create the platform device using
> the
> > resources that are statically declared in the respective mfd_cell.
> 
> It's one possibility.
> 
> > In my case I'd like to have a platform device using the resources
> that are
> > parsed from the ACPI table (i.e. as it is done now by
> > acpi_create_platform_device()).
> 
> So far so good. Nothing prevents you to do that.
> 
> > If my understanding is correct, if I declared an mfd_cell for my IPMI
> child
> > the mfd subsystem would create a platform device for such child and
> > therefore acpi_create_platform_device() would fail to create a new
> platform
> > device as adev->physical_node_count will be non zero.
> > However as things stand now mfd_cell devices can only use the
> resources
> > that are statically defined in the code (and therefore not the ones
> in the
> > ACPI nodes)...am I right?
> 
> You may file resources first and then register MFD cells. See many
> existing examples in the kernel.

Well I had a look around the Kernel I have seen no mfd cells using
Resources that are not statically defined:
i.e. cell->resources in mfd_add_device() always points to statically
defined resource structures.

Usually for ACPI devices first you need to parse the ACPI resources
from the table calling acpi_dev_get_resources(), then you iterate 
over the resource list and fill the resource array by calling
acpi_platform_fill_resurces() (as in acpi_create_platform_device())

With respect to my case are you suggesting dynamically allocate a
resource array and fill it using the same fashion as 
acpi_create_platform_device(), then point cell->resources to such
array before calling mfd_add_device() ?

Thanks
Gab

> 
> --
> With Best Regards,
> Andy Shevchenko