zhhyu7 opened a new pull request, #17667:
URL: https://github.com/apache/nuttx/pull/17667
## Summary
To avoid memory waste, can add support for using an independent iob buffer
The IP protocol often configures CONFIG_IOB_BUFSIZE to be relatively large,
such as 512, for higher throughput. However, the buffer required by CAN is
fixed at a length of 16 or 64. If the system's IOB is directly used,
a lot of memory will be wasted.
## Impact
net/can and can device driver
## Testing
qemu:local
test code:
```
#include <nuttx/can/can.h>
#include <nuttx/config.h>
#include <stdint.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#define CAN_RCV_BUF_MAX 1024
void dump_can_msg(struct can_msg_s* msg, bool tx)
{
if(tx)
printf("---> TX: ");
else
printf("<--- RX: ");
printf("ID 0x%02x, Data ", msg->cm_hdr.ch_id);
for(int i=0;i<can_dlc2bytes(msg->cm_hdr.ch_dlc);i++)
{
printf(" 0x%02x ", msg->cm_data[i]);
}
printf("\n");
}
void build_tx_msg(struct can_msg_s* msg)
{
static uint32_t echo_cnt = 0x120;
memset(msg, 0, sizeof(struct can_msg_s));
msg->cm_hdr.ch_id = 0x123;
msg->cm_hdr.ch_dlc = 8;
msg->cm_data[0] = echo_cnt & 0xff;
msg->cm_data[1] = (echo_cnt >> 8) & 0xff;
echo_cnt++;
}
int main(int argc, FAR char *argv[])
{
printf("Hello, World!!\n");
char buf[CAN_RCV_BUF_MAX];
int nbytes;
int ret;
struct can_msg_s* rxmsg;
struct can_msg_s txmsg;
int fd = open("/dev/can0", O_RDWR | O_CLOEXEC);
if (fd < 0) {
printf("open failed\n");
return -1;
}
while(1)
{
sleep(1);
build_tx_msg(&txmsg);
dump_can_msg(&txmsg, true);
ret = write(fd, &txmsg, sizeof(struct can_msg_s));
if(ret < 0)
{
printf("write failed\n");
return -1;
}
nbytes = read(fd, buf, CAN_RCV_BUF_MAX);
if(nbytes < 0)
{
printf("read failed\n");
return -1;
}
rxmsg = (struct can_msg_s*)buf;
dump_can_msg(rxmsg, false);
}
close(fd);
return 0;
}
```
test log:
```
NuttShell (NSH) NuttX-12.11.0
vela> hello
Hello, World!!
---> TX: ID 0x123, Data 0x20 0x01 0x00 0x00 0x00 0x00 0x00 0x00
<--- RX: ID 0x07, Data 0x20 0x01 0x00 0x00
...
```
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