mmc

Probes all eMMC devices listed in the sysfs /sys/bus/mmc/devices/.

Function Arguments

Name	Type	Description
dir_path	str, None	(optional; default: None) The path used to search for device sysfs data. First all symlinks are resolved, to the the “real” path. Then iteratively search toward parent folder until the remaining path contains the relevent data fields.

Description

This function goes through /sys/bus/mmc/devices/ to read attributes of each eMMC device listed there. Each result should contain these fields:

• device_path: Pathname of the sysfs directory.

• cid: Card Identification Register.

• csd: Card Specific Data Register.

• manfid: Manufacturer ID (from CID Register).

• name: Product Name (from CID Register).

• oemid: OEM/Application ID (from CID Register).

• serial: Product Serial Number (from CID Register).

The result might also contain these optional fields if they are exported in the sysfs entry:

• fwrev: Firmware/Product Revision (from CID Register, SD and MMCv1 only).

• hwrev: Hardware/Product Revision (from CID Register, SD and MMCv1 only).

Please reference the kernel document for more information.

Examples

Let’s say the Chromebook has two eMMC devices. One of which (at /sys/bus/mmc/devices/mmc0:0001) has the attributes:

• cid=123412341234

• ...

And the other one (at /sys/bus/mmc/devices/mmc1:0001) has the attributes:

• cid=246824682468

• ...

Then the probe statement:

{
  "eval": "mmc"
}

will have the corresponding probed result:

[
  {
    "bus_type": "mmc",
    "cid": "123412341234",
    ...
  },
  {
    "bus_type": "mmc",
    "cid": "246824682468",
    ...
  }
]

To verify if the Chromebook has the eMMC device which cid is 123412341234, you can write a probe statement like:

{
  "eval": "mmc",
  "expect": {
    "cid": "123412341234"
  }
}

The corresponding probed result will be empty if and only if there’s no eMMC device which cid is 123412341234 found.

Another use case is that you can ask this function to parse a specific eMMC device sysfs directly like

{
  "eval" "mmc:/sys/bus/mmc/devices/mmc1:0001"
}