On 10/09/2016 02:31 AM, Rob Herring wrote:
> On Thu, Oct 06, 2016 at 01:44:32AM +0530, Nayna wrote:
>>
>>
>> On 09/29/2016 04:34 PM, Jarkko Sakkinen wrote:
>>> On Wed, Sep 28, 2016 at 04:30:40AM -0400, Nayna Jain wrote:
>>>> Virtual TPM, which is being used on IBM POWER7+ and POWER8 systems running
>>>> POWERVM, is currently supported by tpm device driver but lacks the
>>>> documentation. This patch adds the missing documentation for the existing
>>>> support.
>>>>
>>>> Suggested-by: Jason Gunthorpe <jguntho...@obsidianresearch.com>
>>>> Signed-off-by: Nayna Jain <na...@linux.vnet.ibm.com>
>>>> ---
>>>> Changelog v2:
>>>>
>>>> - New Patch
>>>>
>>>> .../devicetree/bindings/security/tpm/ibmvtpm.txt | 41
>>>> ++++++++++++++++++++++
>>>> 1 file changed, 41 insertions(+)
>>>> create mode 100644
>>>> Documentation/devicetree/bindings/security/tpm/ibmvtpm.txt
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/security/tpm/ibmvtpm.txt
>>>> b/Documentation/devicetree/bindings/security/tpm/ibmvtpm.txt
>>>> new file mode 100644
>>>> index 0000000..d89f999
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/security/tpm/ibmvtpm.txt
>>>> @@ -0,0 +1,41 @@
>>>> +* Device Tree Bindings for IBM Virtual Trusted Platform Module(vtpm)
>>>> +
>>>> +Required properties:
>>>> +
>>>> +- compatible : property name that conveys the platform
>>>> architecture
>>>> + identifiers, as 'IBM,vtpm'
>>>> +- device_type : specifies type of virtual device
>>>
>>> A generic device tree question. What is the difference between
>>> these fields? Why the I2C one does have 'device_type'?
>>
>> Please find the details as below:
>>
>> compatible - Standard property name as per IEEE 1275, specifying the
>> interface compatible with this device. This property is consumed by linux
>> kernel for selection of device driver.
>>
>> device_type - Standard property name as per IEEE 1275, specifying the device
>> type. This property MAY be used by linux kernel for device driver selection.
>> It is used in the case of IBM virtual TPM driver.
>
> AIUI, this should be a standard value such as serial, pci, etc. I don't
> think your use here is correct, but I could be wrong. I'm not certain
> what you do with devices that don't have a standard type.
Actually, the vtpm node is a unique device and did not have a standard
type that could be used. That is why the definition in the PAPR gave it
the a new value. The intention was to provide a reasonable type value.
The "IBM," portion of the property value is intended to identify it as
a specific IBM implementation.
Thanks & Regards,
- Nayna
>
>>
>> /**
>> * vio_register_device_node: - Register a new vio device.
>> * @of_node: The OF node for this device.
>> *
>> * Creates and initializes a vio_dev structure from the data in
>> * of_node and adds it to the list of virtual devices.
>> * Returns a pointer to the created vio_dev or NULL if node has
>> * NULL device_type or compatible fields.
>> */
>> struct vio_dev *vio_register_device_node(struct device_node *of_node)
>>
>> and vtpm device table being defined as below:
>>
>> static struct vio_device_id tpm_ibmvtpm_device_table[] = {
>> { "IBM,vtpm", "IBM,vtpm"}, ----------------------------------->
>> type,compat
>> { "", "" }
>> };
>>
>> So, vio (virtual) devices uses both device_type and compatible property for
>> device registration and driver selection.
>> In case of physical TPM, it is only compatible property being used for
>> device driver selection
>>
>> Also, please note that device_type property is now deprecated in latest
>> Device Tree specs.
>
> Deprecated for Flattened DT only. OpenFirmware implementations
> can/should still use this.
>
> Rob
>
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