A generic, multi channel bridge between userspace Linux and PRU allowing for easy and efficient data tranfer.
Each channel is unidirectional and will be represented by sysfs files in userspace.Number of channels has been fixed at 10 but length of each channel can be varied.
int pru_bridge_init(int channel_sizes[NUM_CHANNELS]);
//channel_sizes is a array of 10 int which contain channel sizes
void pru_channel_open(int channel_no,int type);
//type is either PRU_READ or PRU_WRITE depending on channel type
void pru_channel_close(int channel_no);
int pru_write(int channel_no,uint8_t* pru_data,int length);
int pru_read(int channel_no,uint8_t* pru_data,int length);init(channel_sizes)
//channel_sizes is a array of 10 int which contain channel sizes
channel_open(channel_no,channel_type)
channel_close(channel_no)
read(channel_no,data,length)
write(channel_no,data,length)(not sure if all can be implemented due to code size constraints)
int check_init() //returns whether or not driver/channels have been initialisied until this is not '1' pru_bridge cannot be used
int read_buffer(int ring_no,uint8_t* pru_data,int length);
int write_buffer(int ring_no,uint8_t* pru_data,int length);
int check_index(int ring_no);-
- Initialisation : a character array containing the size of channels, seperated by spaces is input to the sysfs file init.The handler first extracts the numbers from the buf being returned by the handler.Then the pru_bridge_init function computes the physical memory locations of each ring of each channel and buffers withing the channels and maps(ioremap) it to kernel memory.Finally the flag for driver initislisation is set to 1.
- Write : write from pru to arm will take place via writing a single byte at a time to a channelno_write sysfs file.This inturn invokes the handler which pru_write function within the driver and writes to the appropriate memory locations. Since the buffers are circular buffers overfows will result in overwriting of oldest valid data.
- Read :To read from a channel libraries read from the channelno_read sysfs file.The handler then reads a single character and writes it to the sysfs file.If the buffer is empty or there is no value to be read -1 is written to the file
All data tranfer reads/writes are logged in the kernel message buffer
-
- Init_check :This simply checks if the driver has initialsied the channels or not
- Write : Multi-byte types can be written and overflow will result in overwritting of oldest data members.
- Read :Read involves passing of a byte pointer which will return a btye array of appropraite length.If there is no data to be read -1 is retuned