Updated: April 19, 2023

Generic information for SDHI memory card, MMC, and eMMC drivers

Note: You must be root or have the right abilities to start this driver.


devb-sdmmc-variant [blk option[,option]..
                   [cam option[,option]...]
                   [disk option[,option]...]
                   [sdmmc option[,option]...]
                   [sdio option[,option]...]
                   [fs_type options]

Runs on:

QNX Neutrino


Note: Use commas (,) to separate the options. You can put the blk, cam, sdmmc, sdio, and disk groups of options in any order.
blk options
The blk options control the driver. If specified, they must follow the blk keyword. For more information, see
cam options
The cam options control If specified, they must follow the cam keyword.
disk options
The disk options control the driver's interface to If specified, they must follow the disk keyword.
sdmmc options:
The sdmmc options control the driver's interface to the SD/MMC device. If there are multiple SD/MMC devices, you can repeat these options for each controller. Remember, however, to specify the sdmmc keyword before each controller's set of options.
This option is specific to the firmware that runs on the eMMC device. With this option, you enable the background operations using one of the following values:
  • on—indicates to the firmware that background operations are required and that the driver will issue commands to allow the eMMC device to perform background operations
  • auto—indicates to the firmware to handle all operations autonomously (as supported in the eMMC 5.1 specification)
By default, this option isn’t enabled.
The bus number of the SDIO controller.
Enable eMMC volatile cache. The default is off.
Enable the eMMC partitions. The default is off.
Set the priority of the processing thread. The default is 21.
Set power off notification mode for the eMMC. The notification can either be short or long.
Set the verbosity level.
sdio options:
The sdio options control the driver's interface to the SD/MMC host controller. If there are multiple host controllers, you can repeat these options for each controller. Remember, however, to specify the sdio keyword before each controller's set of options.
Disable AC12. The default is on.
Disable AC23. The default is on.
The address of the interface.
Disable DMA.
Board-specific options. Run the use message on the target to get more information about the board-specific options available on your target for your driver.
Set/Clear bus widths (4, 8).
Set the operational clock.
The device ID of the controller.
The DMA channel to use.
Set the driver strength value for the HS_TIMING register. The driver strength value controls the impedance at which the HS200- or HS400-compatible eMMC chip drives communication lines to the SoC. The accepted values are 0–4. These values align with the I/O driver strength types listed in the JEDEC eMMC standard (document JESD84).
Note: Not all eMMC chips support driver strength values greater than 0. The default value is 0.
An eMMC device is connected to the interface.
The index of the controller in the machine, where idx is a value between 0 and the number of adapters.
The interrupt used by the controller.
The name of the host controller.
Set the power management idle/sleep time in milliseconds (ms). The default is 100:10000 ms.
Set/Clear timings. The valid values to use are hs, ddr, sdr12, sdr25, sdr50, sdr104, hs200, hs400.
Set the SDIO verbosity level.
fs_type options
The fs_type options control any filesystem (fs-*.so) module being loaded. Here, fs_type is the filesystem type, such as qnx6 for the Power-Safe filesystem. For the list of supported filesystem options, see the reference for the corresponding shared object. For example, for qnx6, see


These are examples for the devb-sdmmc-rcar-gen3 driver.

For an SD memory card:
devb-sdmmc-rcar_gen3 blk cache=64m cam pnp, bounce=128k sdio idx=0
For eMMC Flash:
devb-sdmmc-rcar_gen3 blk cache=64m cam bounce=128k mem name=below4G
                     sdio idx=2, emmc disk name=mmc