DEVMEM Drivers

The devmem driver provides an interface for accessing memory-mapped I/O in an embedded system. This driver allows for reading, writing, and memory mapping of specific memory regions or device registers.

read(): This function reads data from the memory-mapped I/O address

space into the buffer provided by the caller. The first byte read corresponds to the address specified by the device’s “current memory address”. The addresses for subsequent bytes depend on the auto-increment behavior of the specific device.

write(): This function transfers data from the provided data buffer by

the caller to the memory-mapped I/O address space. The first byte written corresponds to the address specified by the device’s “current memory address”.

mmap(): The mmap() function provides a mechanism to map a device’s

memory region into the user space, allowing direct access to device registers or memory regions. The mapped region can be accessed using normal memory operations.

The function requires a base address and size for the memory region to be mapped. If successful, it returns a pointer to the mapped region. If mapping fails, it returns EINVAL and errno is set appropriately.