UM0851 datasheet(95/245 Pages) STMICROELECTRONICS

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UM0851

Communication device drivers

Doc ID 16604 Rev 2

95/245

Figure 24.

SD/SDIO/MMC Linux protocol stack

4.7.3

SDIO/SD/MMC usage in Linux

You can interact with the SDIO/SD/MMC card inserted in the SDIO slot on SPEAr board

from two levels: either from the user level (using the block device interface exposed by the

existing card driver) or from the core driver interface (creating a new card driver).

Using the block device interface

There are few card drivers present in Linux that expose the block device interface to the user

application. You can use /dev/mmcblkp1, /dev/mmcblkp2, etc nodes provided by this layer

for any interaction with the SDIO/SD/MMC card. Once the card is inserted, you can mount

its file system using the above nodes and access it like a normal mass storage device.

Usual operations like cp, mv, rm, etc work fine. You could also create a new file system

structure on the memory card.

# mount /dev/mmcblkp1 /mnt/

Using the MMC core driver interface

The core driver layer provides function calls to use the underlying SDIO hardware. This

section explains how you can create a new card driver. There are few sample drivers

present in Linux which use this interface. They are present at the drivers/mmc/card folder.

The card driver can use functions exposed by the underlying core driver layer. It must

include the following files to access the internal structures of the MMC framework:

include/linux/mmc/core.h, include/linux/mmc/card.h, include/linux/mmc/host.h,

include/linux/mmc/mmc.h

●

Driver registration:

The card driver must register itself with the MMC core layer in order to use the core

driver layer interface. This can be done using the following function.

/* drv: MMC media driver. */

int mmc_register_driver(struct mmc_driver *drv);

struct mmc_driver {

struct device_driver drv;

int (*probe)(struct mmc_card *);

void (*remove)(struct mmc_card *);

User applications

Hardware

Kernel space

User space

SDIO/SD/MMC core

SDIO controller driver

Arasan SDIO controller

Block

UART

WLAN

SDIO

MMC

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