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Message-ID: <1341794461.1682.138.camel@rui.sh.intel.com>
Date: Mon, 09 Jul 2012 08:41:01 +0800
From: Zhang Rui <rui.zhang@...el.com>
To: Benjamin Tissoires <benjamin.tissoires@...il.com>
Cc: khali@...ux-fr.org, ben-linux@...ff.org, w.sang@...gutronix.de,
lenb@...nel.org, linux-acpi@...r.kernel.org,
linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
jkosina@...e.cz, chatty@...c.fr, jj_ding@....com.tw
Subject: Re: Fwd: Hid over I2C and ACPI interaction
On 四, 2012-07-05 at 10:44 +0200, Benjamin Tissoires wrote:
> Hi,
>
> Many thanks for these information. It seems like I was on the right
> track, but I didn't saw the hidden part of the iceberg.
yep.
> I've already written the i2c slave part (and the acpi handling to get
> the HID register by using the DSM should work), but I need now the
> whole ACPI pnp drivers...
>
you need the ACPI/PNP I2C controller driver.
> But without a real ACPI 5.0 mainboard, I think it will be quite
> difficult to implement and debug this ACPI stuff.
>
yes, that's the problem I have. I can not send out the code based on
some example ASL code. :)
thanks,
rui
> Cheers,
> Benjamin
>
> On Thu, Jul 5, 2012 at 9:20 AM, Zhang Rui <rui.zhang@...el.com> wrote:
> > Hah, seems I forgot to reply to Benjamin.
> >
> > On 四, 2012-07-05 at 15:01 +0800, Zhang Rui wrote:
> >> > -------- Original Message --------
> >> > Subject: Hid over I2C and ACPI interaction
> >> > Date: Wed, 4 Jul 2012 15:46:35 +0200
> >> > From: Benjamin Tissoires <benjamin.tissoires@...il.com>
> >> > To: Jean Delvare <khali@...ux-fr.org>, Ben Dooks <ben-linux@...ff.org>, Wolfram
> >> > Sang <w.sang@...gutronix.de>, Len Brown <lenb@...nel.org>,
> >> > <linux-acpi@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
> >> > <linux-kernel@...r.kernel.org>
> >> > CC: Jiri Kosina <jkosina@...e.cz>, Stéphane Chatty <chatty@...c.fr>, JJ Ding
> >> > <jj_ding@....com.tw>
> >> >
> >> > Hi Guys,
> >> >
> >> > I'm the co-author and the maintainer of the hid-multitouch driver. To
> >> > support even more devices, I started the implementation of the HID
> >> > over I2C protocol specification which is introduced by Win8. I'm quite
> >> > comfortable with the hid and the I2C part, but I'm blocked with the
> >> > interaction with the ACPI for the pnp part.
> >> >
> >> > I wanted to have your advice/help on this problem. I've add in the
> >> > recipients list the maintainers of i2c and ACPI, sorry for the noise
> >> > if you don't feel concerned about this.
> >> >
> >> > So, let's go deeper in the problem ;-)
> >> > Microsoft's spec asks the OEM to fill the ACPI DSDT to provide the
> >> > following scope in the ASL layout:
> >> >
> >> > >>>>>>>>> begin of ASL
> >> > Scope (\_SB) {
> >> > //--------------------
> >> > // General Purpose I/O, ports 0...127
> >> > //--------------------
> >> >
> >> > Device(HIDI2C_DEVICE1) {
> >> > Name(_ADR,0)
> >> > Name (_HID, "MSFT1234”)
> >> > Name (_CID, "PNP0C50")
> >> > Name (_UID, 3)
> >> >
> >> > Method(_CRS, 0x0, NotSerialized)
> >> > {
> >> > Name (RBUF, ResourceTemplate ()
> >> > {
> >> > // Address 0x07 on I2C-X (OEM selects this address)
> >> > //IHV SPECIFIC I2C3 = I2C Controller; TGD0 = GPIO Controller;
> >> > I2CSerialBus (0x07, ControllerInitiated,
> >> > 100000,AddressingMode7Bit, "\\_SB.I2C3",,,,)
> >> > GpioInt(Level, ActiveLow, Exclusive, PullUp, 0, "\\_SB. TGD0",
> >> > 0 , ResourceConsumer, , ) {40}
> >> > })
> >> > Return(RBUF)
> >> > }
> >> >
> >> > Method(_DSM, 0x4, NotSerialized)
> >> > {
> >> > // BreakPoint
> >> > Store ("Method _DSM begin", Debug)
> >> >
> >> > // DSM UUID
> >> > switch(ToBuffer(Arg0))
> >> > {
> >> > // ACPI DSM UUID for HIDI2C
> >> > case(ToUUID("3CDFF6F7-4267-4555-AD05-B30A3D8938DE"))
> >> > {
> >> > // DSM function which returns the HID Descriptor
> >> > Address (skipped)
> >> > }
> >> >
> >> > default
> >> > {
> >> > // No other GUIDs supported
> >> > Return(Buffer(One) { 0x00 })
> >> > }
> >> > }
> >> > }
> >> > }
> >> > <<<<<<<<< end of ASL
> >> >
> >> yep, this is an ACPI enumerated I2C controller.
> >>
> >> > Summary:
> >> > - a HID over I2C device has to present the Compatibility ID "PNP0C50"
> >> > - in the _CRS block, the address, the adapter and the gpioInt are
> >> > defined (or referenced)
> >> > - it presents a Device Specific Method (_DSM) which returns the HID
> >> > Descriptor register address. This register is our entry point for
> >> > retrieving the information about our hid device (so it's mandatory to
> >> > obtain it).
> >> >
> >> > Where am I:
> >> > - I've written a first layer on top of i2c that retrieves the hid
> >> > register (currently the address 0x0001 is hardcoded), then get the
> >> > report desccriptors and the input events, and forward all this stuff
> >> > to the hid layer.
> >> > - It's working with a custom emulated HID over i2c touchpad, while
> >> > waiting for the one a manufacturer should send to me.
> >> > - The detection and the addition to the adapter is done by adding the
> >> > address in the lists and the name through the i2c "->detect" callback
> >> > (which is not very good, because I don't have the interrupt line
> >> > there).
> >> > - I've written a first acpi implementation that rely on the
> >> > DEVICE_ACPI_HANDLE macro to get the ACPI handle of the device (if
> >> > available).
> >> > - I'm not able to do some tests with the ACPI, as I don't know how to
> >> > implement this DSDT on my computer (I'm missing the I2C part), and the
> >> > manufacturer returned the mainboard with the right DSDT to the OEM.
> >> >
> >> > My questions:
> >> > - will the current acpi implementation handle I2C devices?
> >>
> >> you still need to write your own device driver for the device.
> >>
> >> > - it seems to me that the .archdata field is left blank during the i2c
> >> > device initialization in all paths I've seen. Is that true?
> >> > - who puts the name int the struct i2c_board_info? (for hot-plugged
> >> > i2c devices).
> >> >
> >> > - finally, what is the best way of handling ACPI for those I2C devices:
> >> > 1) everything is fine, I should have the ACPI handle in .archdata.
> >> > 2) someone has to implement the handling of I2C in the pnpACPI layer
> >> > (by adding I2CSerialBus handling and creating there the i2c slave).
> >> > 3) I should create an acpi driver which handles "PNP0C50" and which
> >> > creates the i2c slaves.
> >> >
> >> exactly.
> >>
> >> As this I2C controller uses the GPIO interrupt, we need an ACPI GPIO
> >> controller driver for interrupts first.
> >> I already have such a patch in hand, but have not release it for some
> >> reason.
> >> Second, you need to write your own PNP I2C controller driver, to
> >> enumerate the I2C controller via ACPI, AND enumerate the I2C slave
> >> devices under this controller to I2C bus. I also have a similar driver
> >> for SPI controller and SD/MMC controller.
> >> Third, you need a I2C slave device driver to handle the I2C slave device
> >> in I2C bus.
> >>
> >> here is a BKM I wrote, hope it helps.
> >>
> >> And also any comments are welcome. :)
> >>
> >> From 0a0fa4ff7b4b06c6560de94a78b15c6adfd86e34 Mon Sep 17 00:00:00 2001
> >> From: Zhang Rui <rui.zhang@...el.com>
> >> Date: Mon, 26 Dec 2011 10:42:04 +0800
> >>
> >> As many SoC IP blocks are not hardware self-enumerable, the
> >> firmware, aka, ACPI tables, is responsible for
> >> enumerating/reserving/assigning system resources to these
> >> devices. This tutorial talks about how to enumerate these
> >> devices via ACPI namespace.
> >>
> >> Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> >> ---
> >> Documentation/acpi/acpi-device-probing.txt | 466
> >> ++++++++++++++++++++++++++++
> >> 1 file changed, 466 insertions(+)
> >> create mode 100644 Documentation/acpi/acpi-device-probing.txt
> >>
> >> diff --git a/Documentation/acpi/acpi-device-probing.txt
> >> b/Documentation/acpi/acpi-device-probing.txt
> >> new file mode 100644
> >> index 0000000..82efbf3
> >> --- /dev/null
> >> +++ b/Documentation/acpi/acpi-device-probing.txt
> >> @@ -0,0 +1,466 @@
> >> +
> >> +HOWTO enumerate devices via ACPI
> >> +
> >> +Copyright (c) 2011-2012 Intel Corporation
> >> +
> >> +Contrast to hardware self-enumerable devices(e.g. USB, PCI) on PC
> >> platform,
> >> +many SoC IP blocks can not be self enumerated.
> >> +We used to introduce platform specific code for these devices.
> >> +But now, with ACPI 5.0, there is no requirement for the hardware to be
> >> +self-discoverable, enumerable or re-locatable, as the firmware is
> >> responsible
> >> +for enumerating/reserving/assigning system resources (such as address
> >> ranges or
> >> +interrupts) to the device.
> >> +
> >> +This document will show how to enumerate and configure a device via
> >> ACPI.
> >> +If you want to get more details about why and when we need this,
> >> +please refer to ACPI spec 5.0 and
> >> +Intel Architecture Platform Compatibility Definition.
> >> +
> >> +Note that although these are ACPI devices, we prefer to use PnP drivers
> >> for them,
> >> +this is because:
> >> +1. all the non-ACPI-predefined Devices are exported as PnP devices as
> >> well
> >> +2. PnP bus is a well designed bus. Probing via PnP layer saves a lot of
> >> work
> >> + for the device driver, e.g. getting & parsing ACPI resources.
> >> +
> >> +=============================================================================
> >> +1. Understand device definition in ACPI namespace
> >> + [Case study 1] SD/MMC controller
> >> +2. Driver for a leaf device
> >> + 2.1 Make a list of supported PnP ids
> >> + 2.2 Implement .probe/.remove callbacks for the PnP driver
> >> + 2.3 Fill in the pnp_driver structure
> >> + 2.4 Register the PnP driver
> >> +3. Driver for a master device on a non-self-enumerable bus
> >> + [Case Study 2] SPI controller and its slave device
> >> + 3.1 Probe the master device
> >> + 3.2 Walk ACPI namesapce to get the child devices of the master
> >> device
> >> + 3.3 Register these child devices as slave devices
> >> + 3.4 Write slave device driver
> >> +4. Misc
> >> +=============================================================================
> >> +
> >> +-----------------------------------------------------------------------------
> >> +1. Understand device definition in ACPI namespace
> >> +-----------------------------------------------------------------------------
> >> +
> >> +To enumerate a device in ACPI namespace, we need to find out and
> >> understand
> >> +HOW the device is defined in ACPI namespace first.
> >> +
> >> +[Case study 1 ] SD/MMC Controller
> >> +
> >> +Here is an ASL example code for SD/MMC controller definition in ACPI
> >> namespace.
> >> +
> >> + Device (EMMC)
> >> + {
> >> + Name (_ADR, Zero)
> >> + /* I use PNPXXXX, an arbitrary string, here, as PnP id is
> >> device specific */
> >> + Name (_HID, "PNPXXXX")
> >> + Name (_CID, "PNPXXXX")
> >> + Name (_UID, 4)
> >> +
> >> + Method (_CRS, 0, NotSerialized)
> >> + {
> >> + Name (RBUF, ResourceTemplate ()
> >> + {
> >> + Memory32Fixed (ReadWrite,
> >> + 0xFFA50000, // Address Base
> >> + 0x00000100, // Address Length
> >> + )
> >> + Interrupt (ResourceConsumer, Level, ActiveLow,
> >> Exclusive, ,, )
> >> + {
> >> + 0x0000001b,
> >> + }
> >> + })
> >> + Return (RBUF)
> >> + }
> >> +
> >> + Method (_STA, 0, NotSerialized)
> >> + {
> >> + Return (0x0F)
> >> + }
> >> + }
> >> +
> >> +_ADR : the address of this device on its parent bus. Useless in this
> >> case.
> >> +_HID : the PnP id for this device.
> >> +_CID : the compatible PnP id. use this as the PnP id if _HID doesn't
> >> exist.
> >> +_CRS : the system resources currently allocated to this device.
> >> + the Memory32Fixed part shows an Mem space for the device,
> >> + and the Interrupt part shows the device interrupt.
> >> +_STA : the current status of the device, e.g. it's
> >> enabled/disabled/removed.
> >> +
> >> +By reading this example ASL code, we should know that there is a SD/MMC
> >> controller
> >> +on this platform, it's mem space base address is 0xFFA50000, length is
> >> 0x00000100,
> >> +and the irq for this device is 0x1b.
> >> +
> >> +In Chapter 2, we will use this piece of ASL code as an example to
> >> +show how to probe the SD/MMC controller via ACPI namespace.
> >> +
> >> +-----------------------------------------------------------------------------
> >> +2 Driver for a leaf device
> >> +-----------------------------------------------------------------------------
> >> +
> >> +2.1 Make a list of supported pnp ids.
> >> +
> >> +Use the string in _HID or _CID objects as the PnP ids so that the
> >> device can
> >> +be attached to the driver successfully.
> >> +
> >> +In this case,
> >> +struct pnp_device_id sdhci_pnp_ids[] = {
> >> + { .id = "PNPXXXX",
> >> + .driver_data = (unsigned long)&sdhci_mfd_pdata },
> >> + { },
> >> +};
> >> +
> >> +2.2 Implement the .probe and .remove callback of PnP driver.
> >> +
> >> +If you're not clear about what should be done in the driver, you can
> >> consult
> >> +some similar driver, for example, drivers/mmc/host/sdhci-pci.c shows
> >> how
> >> +to probe a PCI SD/MMC controller, this helps us understand what should
> >> be done
> >> +in the .probe/.remove callback.
> >> +
> >> +By reading the sdhci-pci .probe function, we know that the .probe
> >> callback
> >> +needs to
> >> +a) alloc a sdhci host.
> >> +b) fill the sdhci host structure with necessary resources got from
> >> + PCI configure space, including irq and mem space for the sdhci host.
> >> +c) register the sdhci host.
> >> +And then, driver/mmc/host/sdhci.c, the SDHCI interface driver will
> >> handle
> >> +everything for us.
> >> +
> >> +So, basically, we need to do the same work in sdhci_pnp_probe callback,
> >> +except that we need to get the information from ACPI namesapce instead.
> >> +
> >> +To get the resources in _CRS, we do not need Linux ACPICA APIs as PnP
> >> layer
> >> +has done this for us already.
> >> +
> >> +pnp_irq() returns the device irq, which equals the "Interrupt" part in
> >> _CRS method.
> >> +pnp_get_resource(, IORESOURCE_MEM, 0) returns the first Mem space base
> >> address
> >> +and length of this device, which equals the "Memory32Fixed" Part of the
> >> _CRS.
> >> +
> >> +the code below shows how to use the PnP APIs to get ACPI resources and
> >> +register a sdhci host in the .probe callback.
> >> +
> >> +static int __devinit
> >> +sdhci_pnp_probe(struct pnp_dev *pdev, const struct pnp_device_id
> >> *dev_id)
> >> +{
> >> +...
> >> + pnp_disable_dev(pdev);
> >> + ret = pnp_activate_dev(pdev);
> >> +...
> >> + iomem = pnp_get_resource(pdev, IORESOURCE_MEM, 0);
> >> +...
> >> + host = sdhci_alloc_host(&pdev->dev, sizeof(struct sdhci_pnp_dev));
> >> +...
> >> + host->irq = pnp_irq(pdev, 0);
> >> +...
> >> + if (!request_mem_region(iomem->start, resource_size(iomem),
> >> + mmc_hostname(host->mmc))) {
> >> +...
> >> + host->ioaddr = ioremap_nocache(iomem->start,
> >> resource_size(iomem));
> >> +...
> >> + ret = sdhci_add_host(host);
> >> +...
> >> + pnp_set_drvdata(pdev, sdhci);
> >> +...
> >> +}
> >> +
> >> +Once the .probe callback is done, we just need to release the resources
> >> and
> >> +unregister the host in the .remove callback.
> >> +
> >> +static void sdhci_pnp_remove(struct pnp_dev * pdev)
> >> +{
> >> + struct sdhci_pnp_dev *sdhci = pnp_get_drvdata(pdev);
> >> + struct resources *iomem = pnp_get_resource(pdev, IORESOURCE_MEM, 0);
> >> +...
> >> + sdhci_remove_host(sdhci->host, dead);
> >> + sdhci_free_host(sdhci->host);
> >> + iounmap(sdhci->host->ioaddr);
> >> + release_mem_region(iomem->start, resource_size(iomem));
> >> + pnp_set_drvdata(pdev, NULL);
> >> + pnp_disable_dev(pdev);
> >> +}
> >> +
> >> +2.3 Fill in the pnp_driver structure
> >> +
> >> +Next step is to fill in the pnp_driver structure with PnP ids and
> >> +.probe/.remove callbacks finished in section 2.1 and 2.2
> >> +
> >> +static struct pnp_driver sdhci_pnp_driver = {
> >> + .name = DRIVER_NAME,
> >> + .id_table = sdhci_pnp_ids,
> >> + .probe = sdhci_pnp_probe,
> >> + .remove = __devexit_p(sdhci_pnp_remove),
> >> +};
> >> +
> >> +Note that .name and .id_table cannot be NULL.
> >> +
> >> +2.4 Register the PnP driver
> >> +
> >> +Now we can register this PnP driver to the driver model.
> >> +
> >> +static int __init sdhci_pnp_init(void)
> >> +{
> >> + return pnp_register_driver(&sdhci_pnp_driver);
> >> +}
> >> +
> >> +module_init(sdhci_pnp_init);
> >> +
> >> +
> >> +-----------------------------------------------------------------------------
> >> +3 Driver for a master device on a non-self-enumerable bus
> >> +-----------------------------------------------------------------------------
> >> +In some cases, enumerating via ACPI brings new requirements in the
> >> driver.
> >> +For example, the driver for a master device on a non-self-enumerable
> >> bus is
> >> +responsible for enumerating the slave devices on this bus as well,
> >> which are
> >> +described as child devices of this master device in ACPI namespace.
> >> +
> >> +Taking SPI bus for example,
> >> +
> >> +-------------------------------------------------------------------
> >> +PNP/ACPI layer
> >> +
> >> + spi-acpi driver
> >> + |
> >> + |-----------------|
> >> + | |
> >> + | |
> >> + V V
> >> + register itself register its children
> >> + as a master as slave devices
> >> + device |
> >> + | |
> >> +---------|-----------------|---------------------------------------
> >> + | |
> >> + | |
> >> + | |
> >> + V V
> >> + -------------- -----------
> >> + | SPI | | SPI |
> >> + | master | | slave |
> >> + -------------- -----------
> >> + ^
> >> + |
> >> + |
> >> + V
> >> + -----------------------------
> >> + | SPI slave driver driver |
> >> + -----------------------------
> >> +SPI Bus layer
> >> +-------------------------------------------------------------------
> >> +
> >> +The figure above shows the components needed to make a SPI slave device
> >> work
> >> +a) an PNP/ACPI driver to probe the SPI master and its slaves.
> >> +b) a SPI slave device driver for the SPI slave device.
> >> +
> >> +[Case Study 2] SPI controller and its slave device
> >> +
> >> +This piece of ASL code shows the definition of a SPI controller and its
> >> slave device,
> >> +MAX3110, in ACPI namespace.
> >> +
> >> +Device (SPI1) {
> >> + Name (_ADR, 0)
> >> + Name (_HID, "PNPYYYY")
> >> + Name (_CID, "PNPYYYY")
> >> + Name (_UID, 1)
> >> +
> >> + Method (_CRS, 0x0, NotSerialized) {
> >> + Name (RBUF, ResourceTemplate ()
> >> + {
> >> + Memory32Fixed (ReadWrite, 0xff128400, 0x00000400)
> >> + Interrupt(ResourceConsumer, Level, ActiveHigh, Exclusive, , , )
> >> {0x09}
> >> + })
> >> + Return (RBUF)
> >> + }
> >> +
> >> + Method (_STA, 0x0, NotSerialized) {
> >> + Return(0xf)
> >> + }
> >> +
> >> + Device(MAX0)
> >> + {
> >> + Name(_HID, "PNPZZZZ") // Max3110 serial port
> >> + Name(_DDN, "Max3110 serial port")
> >> + Method(_CRS, 0x0, NotSerialized)
> >> + {
> >> + // SpiSerial Bus Connection Descriptor
> >> + Name(UBUF, ResourceTemplate () {
> >> + SPISerialBus(
> >> + 1, // Device selection
> >> + PolarityHigh, // Device selection polarity
> >> + ThreeWireMode, // wiremode
> >> + 8, // databit len
> >> + ControllerInitiated, // slave mode
> >> + 1000, // Connection speed
> >> + ClockPolarityHigh, // Clock polarity
> >> + ClockPhaseFirst, // clock phase
> >> + "\\_SB.SPI1", // ResourceSource: SPI bus controller name
> >> + 0, // ResourceSourceIndex
> >> + ResourceConsumer, // Resource usage
> >> + , // DescriptorName: creates name for offset
> >> of resource descriptor
> >> + ) // Vendor Data
> >> + // OUT pin, BT_EN pin Core GPIO 74
> >> + GpioIo(Exclusive, PullDefault, 0, 0, IoRestrictionOutputOnly, "\
> >> \_SB.GPIS", ) {0x4A}
> >> + })
> >> +
> >> + Return (UBUF)
> >> + }
> >> + }
> >> +}
> >> +
> >> +By reading the ASL code, we can see that
> >> +a) There is a SPI controller on this platform.
> >> + with IRQ 0x09, and a 0x400 bytes Memory space started from
> >> 0xff128400.
> >> +b) a MAX3110 device is connect to a SPI controller.
> >> + all the information required for probing a SPI slave device is
> >> described
> >> + in the "SPISerailBus" part of the MAX0._CRS method.
> >> +
> >> +We will talk about how to probe these two devices in this chapter.
> >> +
> >> +3.1 Probe the master device
> >> +
> >> +Please follow the Chapter 2 to probe the SPI master device.
> >> +
> >> +static int __devinit
> >> +dw_spi_pnp_probe(struct pnp_dev *pdev, const struct pnp_device_id
> >> *dev_id)
> >> +{
> >> +...
> >> + dws->paddr = pnp_mem_start(pdev, 0);
> >> + dws->iolen = pnp_mem_len(pdev, 0);
> >> + dws->irq = pnp_irq(pdev, 0);
> >> + dws->parent_dev = &pdev->dev;
> >> + dws->bus_num = index++;
> >> + dws->num_cs = 4;
> >> + dws->regs = ioremap_nocache((unsigned long)dws->paddr,
> >> + dws->iolen);
> >> +...
> >> + ret = dw_spi_mid_init(dws);
> >> +...
> >> + ret = dw_spi_add_host(dws);
> >> +...
> >> +}
> >> +
> >> +3.2 Walk ACPI namespace to probe all its child devices.
> >> +
> >> +As MAX3110 can not be enumerated automatically, we introduce
> >> +dw_spi_pnp_slaves_register() to find the MAX3110 device in ACPI
> >> namespace
> >> +
> >> +static int __devinit dw_spi_pnp_slaves_register(struct dw_spi_pnp*
> >> dwpnp)
> >> +{
> >> + ...
> >> + struct acpi_device *adev;
> >> + adev = dwpnp->pdev->data;
> >> +
> >> + /*
> >> + * find spi child devices given in ACPI namespace, one lower level
> >> only
> >> + */
> >> + status = acpi_walk_namespace(ACPI_TYPE_DEVICE, adev->handle, 1,
> >> + spi_slave_register, NULL,
> >> + spi_slave_info, NULL);
> >> + ...
> >> +}
> >> +
> >> +3.3 Register its child devices as slave devices
> >> +
> >> +As spi_slave_register is invoked for each SPI1 child device,
> >> +we introduce spi_slave_fill_resourcetry and try to register
> >> +SPI slave devices in spi_slave_register.
> >> +
> >> +acpi_status __init spi_slave_register(acpi_handle spi_slave_handle, u32
> >> level,
> >> + void* data, void** return_value)
> >> +{
> >> + ...
> >> + struct spi_board_info *spi_slave_info;
> >> + ...
> >> + status = acpi_walk_resources(spi_slave_handle, METHOD_NAME__CRS,
> >> + spi_slave_fill_resource, data);
> >> + ...
> >> + /* register SPI slave device */
> >> + ret = spi_register_board_info(spi_slave_info, 1);
> >> + ...
> >> +}
> >> +
> >> +acpi_status __devinit spi_slave_fill_resource(struct acpi_resource
> >> *resource, void* data)
> >> +{
> >> + struct spi_board_info *spi_slave_info;
> >> + struct acpi_resource_spi_serialbus *spi_resource;
> >> + ...
> >> + spi_resource = &resource->data.spi_serial_bus;
> >> + spi_slave_info->chip_select = spi_resource->device_selection;
> >> + spi_slave_info->max_speed_hz = spi_resource->connection_speed;
> >> + spi_slave_info->mode = (spi_resource->clock_phase ? SPI_CPHA : 0) |
> >> + (spi_resource->clock_polarity ? SPI_CPOL : 0) |
> >> + (spi_resource->device_polarity ? SPI_CS_HIGH : 0) |
> >> + (spi_resource->wire_mode ? SPI_3WIRE : 0);
> >> + ...
> >> +}
> >> +
> >> +3.4 Write the slave device driver
> >> +
> >> +After 3.3 is done, the MAX3110 device is an slave device in the SPI
> >> bus,
> >> +but to make it work properly, we still need a SPI slave device driver.
> >> +
> >> +Note that this is a general SPI drivers independent of ACPI.
> >> +
> >> +We will not go into details of the slave device driver here as
> >> +this piece of code is bus/device specific.
> >> +
> >> +-----------------------------------------------------------------------------
> >> +4 Misc
> >> +-----------------------------------------------------------------------------
> >> +
> >> +4.1 Note
> >> +
> >> +As ACPI 5.0 is still in heavily developing, if you are unable to find
> >> out all the
> >> +required information for probing a device in ACPI namespace, it is
> >> possible
> >> +that the ASL code is not well written.
> >> +Please contact Zhang Rui <rui.zhang@...el.com> with the acpidump output
> >> of your
> >> +platform attached if you suspect it's an BIOS problem.
> >> +
> >> +4.2 Some important ACPICA APIs for device driver implementation:
> >> +
> >> +-- acpi_status
> >> + acpi_walk_namespace(acpi_object_type type,
> >> + acpi_handle start_object,
> >> + u32 max_depth,
> >> + acpi_walk_callback pre_order_visit,
> >> + acpi_walk_callback post_order_visit,
> >> + void *context, void **return_value);
> >> +Traverse ACPI namespace subtree rooted at start_object, go down
> >> max_depth level
> >> +at most. Call pre_order_visit when the proper node with type is found
> >> the first
> >> +time, call post_order_visit is the node is previously visited. Context
> >> and
> >> +return_value is passed down during the traverse.
> >> +
> >> +And the prototype of acpi_walk_callback:
> >> +typedef
> >> +acpi_status(*acpi_walk_callback) (acpi_handle object,
> >> + u32 nesting_level,
> >> + void *context, void **return_value);
> >> +
> >> +-- acpi_status
> >> + acpi_get_handle(acpi_handle parent,
> >> + acpi_string pathname, acpi_handle * ret_handle);
> >> +Try to get handle with specified pathname under node parent. Usually
> >> used to
> >> +check whether a particular node is available or not.
> >> +
> >> +-- acpi_status
> >> + acpi_get_object_info(acpi_handle object,
> >> + struct acpi_device_info **return_buffer);
> >> +Get acpi_device_info from object handle. Useful for retrieving ACPI
> >> object
> >> +name, type, and status etc.
> >> +
> >> +-- acpi_status
> >> + acpi_walk_resources(acpi_handle device,
> >> + char *name,
> >> + acpi_walk_resource_callback user_function, void *context);
> >> +Traverse resource node specified by name(e.g. METHOD_NAME__CRS) in ACPI
> >> +namespace subtree rooted at device. Call user_function for each entry
> >> in
> >> +acpi_resource list. The list may containe acpi_resource entries with
> >> various
> >> +types. So it is important to handle the interested resource type
> >> properly.
> >> +The acpi_resource with ACPI_RESOURCE_TYPE_END_TAG indicates
> >> end-of-list.
> >> +
> >> +And the prototype of acpi_walk_resource_callback:
> >> +typedef
> >> +acpi_status(*acpi_walk_resource_callback) (struct acpi_resource *
> >> resource,
> >> + void *context);
> >> +
> >> +More ACPICA external interfaces available in include/acpi/acpixf.h
> >
> >
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