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L4Re Operating System Framework
Interface and Usage Documentation
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L4Re Operating System Framework
Interface and Usage Documentation
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The eMMC driver is a driver for PCI Express eMMC controllers.
The eMMC driver can be started with Lua like this:
First, an IPC gate (emmc_bus) is created which is used between the eMMC driver and a client to request access to a particular disk or partition. The server side is assigned to the mandatory svr capability of the eMMC driver. See the section below on how to configure access to a disk or partition.
The eMMC driver needs access to a virtual bus capability (vbus). On the virtual bus the eMMC driver searches for eMMC compliant storage controllers. Please see io's documentation about how to setup a virtual bus.
The eMMC driver supports SDHCI and SDHI controllers, in particular
vbus
Required for finding the device which should be driven by this driver.
Mandatory capability.
client
Static client
Multiple capability names can be provided by the --client command line parameter.
bbds
Only used by the SDHCI driver. Certain SDHCI devices cannot handle DMA requests with DMA buffers beyond 4GiB. The provided dataspace is used as bounce buffer if the driver detects that a certain request needs it. Note: The bounce buffer needs to be able to hold the memory for an entire read/write request. That means that the buffer is divided into the number of maximum segments (see --max-seg parameter).
sdhci_adma_buf
Only used by the SDHCI driver. Page (4096 bytes) for storing DMA descriptors for the SDHCI driver. If this capability is not provided, the driver will allocate an arbitrary page.
bcm2835_mbox_mem
Only used by the SDHCI driver when attaching to an bcm2711-compatible device. Page (4096 bytes) for storing bcm2835 mbox messages. The firmware mbox is used to perform voltage switching for certain SD card configurations. If this capability is not provided, the driver will allocate an arbitrary page.
svr
Server Capability of application. Endpoint for IPC calls
Mandatory capability.
In the example above the eMMC driver is started in its default configuration. To customize the configuration of the eMMC driver it accepts the following command line options:
-v, --verbose
Enable verbose mode. You can repeat this option to increase verbosity up to trace level.
Can be used up to 3 times.
Flag. True if provided.
-q, --quiet
This option enables the quiet mode. All output is silenced.
Flag. True if provided.
--disable-mode <mode>
This option allows to disable certain eMMC/SD card modes from autodetection. Modes with the hs-prefix are determined for eMMC devices, others are for SD card devices.
Can be used multiple times.
Possible values for <mode> are hs26, hs52, hs52_ddr, hs200, hs400, sdr12, sdr25, sdr50, sdr104, ddr50
--max-seg <max>
Maximum number of segments per request. This number is announced to the virtio interface and is also relevant for the required bounce buffer size, see below.
Numerical value.
Default: 64
--client <cap_name>
Connect a static client.
Can be used multiple times.
Name of a provided capability with server rights that adheres to the ipc protocol.
This parameter opens a scope for the following subparameters:
--device <UUID>
This option denotes the partition UUID of the partition to be exported for the client specified in the preceding client option.
String value.
--ds-max <max>
This option sets the upper limit of the number of dataspaces the client is able to register with the eMMC driver for virtio DMA.
Numerical value.
Default: 2
--readonly
This option sets the access to disks or partitions to read only for the preceding client option.
Flag. True if provided.
--dma-map-all
Map the entire client dataspace into the DMA space at the first I/O request and never unmap the dataspace until the client is destroyed. The default behavior is to map the relevant part of the dataspace before an I/O request and unmap it after the request.
Flag. True if provided.
Prior to connecting a client to a virtual block session it has to be created using the following Lua function. It has to be called on the client side of the IPC gate capability whose server side is bound to the eMMC driver.
Call: create(0, "device=<UUID>" [, "ds-max=<max>", "readonly", "dma-map- all"])
"device=<UUID>"
This string denotes a partition UUID the client wants to be exported via the Virtio block interface.
String value.
"ds-max=<max>"
Specifies the upper limit of the number of dataspaces the client is allowed to register with the eMMC driver for virtio DMA.
Numerical value.
Default: 2
"readonly"
This option sets the access to disks or partitions to read only for this client connection.
Flag. True if provided.
"dma-map-all"
Map the entire client dataspace into the DMA space at the first I/O request and never unmap the dataspace until the client is destroyed. The default behavior is to map the relevant part of the dataspace before an I/O request and unmap it after the request.
Flag. True if provided.
If the create() call is successful, a new capability which references an eMMC virtio driver is returned. A client uses this capability to communicate with the eMMC driver using the Virtio block protocol.
A couple of examples on how to request different disks or partitions are listed below.
A more elaborate example with a static client. The client uses the client side of the emmc_cl1 capability to communicate with the eMMC driver.
Accessing a device from QEMU:
The file pcie-ecam.io contains an IO config file which is able to use the QEMU PCI controller to search for attached eMMC devices.
eMMC emulation with QEMU:
The attached patch extends QEMU SD card emulation to emulate eMMC devices. After applying the patch and recompiling QEMU, attach the following parameters to your QEMU command line (assuming that $HOME/foobar.img is the eMMC medium):
1.15.0