On Fri, Aug 14, 2015 at 12:31:32PM -0700, Dustin Byford wrote:
>
> (v2 corrects cc: list)
And adding Mika to the cc-list who is our I2C and ACPI expert.
Mika can you have a look at this and the other patches Dustin sent
recently to the i2c list?
Thanks,
Wolfram
>
> I would like to add support for scanning I2C devices connected to ACPI
> OF compatible muxes described in ASL like this:
>
> Device (MUX0)
> {
> Name (_ADR, 0x70)
> Name (_HID, "PRP0001")
> Name (_CRS, ResourceTemplate()
> {
> I2cSerialBus (0x70, ControllerInitiated, I2C_SPEED,
> AddressingMode7Bit, "^^SMB2", 0x00,
> ResourceConsumer,,)
> })
> Name (_DSD, Package ()
> {
> ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
> Package () {
> Package (2) { "compatible", "nxp,pca9548" },
> }
> })
>
> // MUX channels
> Device (CH00) { Name (_ADR, 0x0) }
> }
>
> Scope(MUX0.CH00)
> {
> Device (TMP0) {
> /* Temp sensor ASL, for example. */
> }
> }
>
> It seems like a reasonable way to describe a common I2C component and
> kernel support is almost there.
>
> I had to:
>
> 1) Find and set an ACPI companion for the "virtual" I2C adapters created
> for each mux channel.
>
> 2) Make sure to scan adap.dev when registering devices under each mux
> channel.
>
> At first, I was confused about why adap.dev->parent is used in
> acpi_i2c_register_devices(). I found b34bb1ee from 4/2013 (ACPI / I2C:
> Use parent's ACPI_HANDLE()), which offers an explanation.
>
> This patch works well, but I'm not sure about the code to just fall back
> to using adap.dev when adap.dev->parent doesn't have an ACPI companion.
> Is there a more explicit check I can make to determine if the adapter
> represents a mux channel?
>
> Any feedback would be welcome. Thanks,
>
> --Dustin
>
> Dustin Byford (1):
> i2c: acpi: scan ACPI enumerated I2C mux channels
>
> drivers/i2c/i2c-core.c | 10 ++++++++++
> drivers/i2c/i2c-mux.c | 8 ++++++++
> 2 files changed, 18 insertions(+)
>
> --
> 2.1.4
>
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