linux-kernel - Re: [PATCH] spi: spi-fsl-dspi: Add ACPI support

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Date:   Wed, 26 Aug 2020 19:09:50 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Kuldip Dwivedi <kuldip.dwivedi@...esoftware.com>
Cc:     Mark Brown <broonie@...nel.org>, Qiang Zhao <qiang.zhao@....com>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pankaj Bansal <pankaj.bansal@....com>,
        Varun Sethi <V.Sethi@....com>,
        Tanveer Alam <tanveer.alam@...esoftware.com>
Subject: Re: [PATCH] spi: spi-fsl-dspi: Add ACPI support

On Wed, Aug 26, 2020 at 08:43:20PM +0530, Kuldip Dwivedi wrote:
> Just a query, Can't we use meaningful HID for different SoC just like
> compatible strings in DT ?
> In this way Silicon parameters can also be added in
> fsl_dspi_devtype_data structure , which is already exist in driver

I don't know, is that the preferred way?
I don't even know if NXP0005 is made up or if it's written down
somewhere in the PNP ID registry. NXP0006 seems to be assigned to the
MDIO controller already, so the list of _HID values for the DSPI
controller would be discontiguous at best, as well as ever-growing.
Again, I'm just raising the concern, if somebody comes in and declares
that as "not a problem", then ok.
In the ACPI spec there's also a _HRV (Hardware Revision) object, which
comes as a simple DWORD. We could use acpi_evaluate_integer() to read
that, and use it as index into the array of fsl_dspi_devtype_data, if
we declare that as ABI within the driver (and new SoCs would be added
only at the end of the enum). Then we could use the NXP0005 _HID for
everything DSPI.
Again, maybe somebody could chime in and guide us on what's preferable.

Thanks,
-Vladimir