Re: [PATCH v2] spi/acpi: enumerate all SPI slaves in the namespace

["Life is hard, and then you die" <ronald@innovation.ch>]

On Thu, May 30, 2019 at 01:16:34PM +0200, Ard Biesheuvel wrote:
> Currently, the ACPI enumeration that takes place when registering a
> SPI master only considers immediate child devices in the ACPI namespace,
> rather than checking the ResourceSource field in the SpiSerialBus()
> resource descriptor.
> 
> This is incorrect: SPI slaves could reside anywhere in the ACPI
> namespace, and so we should enumerate the entire namespace and look for
> any device that refers to the newly registered SPI master in its
> resource descriptor.
> 
> So refactor the existing code and use a lookup structure so that
> allocating the SPI device structure is deferred until we have identified
> the device as an actual child of the controller. This approach is
> loosely based on the way the I2C subsystem handles ACPI enumeration.
> 
> Note that Apple x86 hardware does not rely on SpiSerialBus() resources
> in _CRS but uses nested devices below the controller's device node in
> the ACPI namespace, with a special set of device properties. This means
> we have to take care to only parse those properties for device nodes
> that are direct children of the controller node.
> 
> Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
> Cc: linux-spi@vger.kernel.org
> Cc: broonie@kernel.org
> Cc: andy.shevchenko@gmail.com
> Cc: masahisa.kojima@linaro.org
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> Cc: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> Cc: linux-acpi@vger.kernel.org
> Cc: Lukas Wunner <lukas@wunner.de>
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/spi/spi.c | 103 ++++++++++++++------
>  1 file changed, 72 insertions(+), 31 deletions(-)
[snip]

FYI, I tested this on a MacBook Pro where the (SPI) keyboard driver
depends on those special device properties, and verified this patch
doesn't break anything there.


  Cheers,

  Ronald