1. Kernel MMC/SD driver framework
There are three subdirectories under the kernel drivers/mmc directory: card/, core/, and host/, which just represent the three levels of MMC/SD drivers, as follows:
1) Block layer
Provides file operation interfaces to the file system layer and user space. The main file is block.c in the card/directory. queue.c provides it with several functions to operate the queue.
The block layer calls the interfaces provided by core.c and sysfs.c in the core/directory to identify the partitions of the storage card, read and write the storage card, and other functions.
2) Core layer
The core layer code is in the core/directory. It encapsulates the MMC/SD commands and implements the MMC/SD protocol. It calls the interface of the host controller layer to complete the identification, setting, reading and writing of the memory card.
It can be seen that the MMC/SD interface connection on the development board is: nCD is connected to the external interrupt pin EINT16, and an interrupt will be triggered when the memory card is connected or removed.
Porting the MMC/SD/SDIO controller driver is divided into three steps: patching, adding MMC/SD platform devices, and modifying the host controller driver to specify the nCD interrupt in the above figure.
1) Patch the kernel
2) Add MMC/SD platform equipment
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Professor at Beihang University, dedicated to promoting microcontrollers and embedded systems for over 20 years.
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