不知道这是否与C相关或与Linux内核有关。我正在使用Beaglebone的SPI库BlackLib,它具有SPI传输功能。
出于某种原因,当我第一次尝试时它不起作用。我玩了好几天,直到在[[function本身内声明了两个随机数组时,即使它的效果为零,它还是意外地起作用了。如果删除它们,该功能将在ioctl行再次中断。
例如,如果我打电话:uint8_t writeBuffer[2] = {0x00, 0x01};
uint8_t readBuffer[2] = {0,0};
transfer(writeBuffer, readBuffer, sizeof(readBuffer), 10, 0)
在:功能
bool BlackSPI::transfer(uint8_t *writeBuffer, uint8_t *readBuffer, size_t bufferSize, uint16_t wait_us, uint16_t pad)
{
uint8_t tempReadBuffer[ bufferSize ];
memset( tempReadBuffer, 0, bufferSize);
spi_ioc_transfer package;
package.tx_buf = (unsigned long)writeBuffer;
package.rx_buf = (unsigned long)tempReadBuffer;
package.len = bufferSize;
package.delay_usecs = wait_us;
package.speed_hz = 5000000; //uint32_t
package.bits_per_word = 8; //uint8_t
package.pad = pad;
// IF I DELETE THESE TWO DECLARATIONS, SPI transfer will fail.
// I have no idea why.. maybe causing a specific delay in the code that lets spi work, or overwriting old memory addresses that c++ attemps to access?
uint8_t arr[4] = {0x02, 0x03, 0x04, 0x05};
uint8_t arrr[4] = {0x03, 0x04, 0x05, 0x06};
//ioctl call
if( ::ioctl(this->spiFD, SPI_IOC_MESSAGE(1), &package) >= 0){
memcpy(readBuffer, tempReadBuffer, bufferSize+pad);
return true;
} else {
return false;
}
}
它返回true(有效)。但是,如果我像这样注释掉2个数组,则>]
//uint8_t arr[4] = {0x02, 0x03, 0x04, 0x05}; //uint8_t arrr[4] = {0x03, 0x04, 0x05, 0x06};
该函数返回false(无效),并且strace
输出包含:
ioctl(4, 0x40206b00, 0xbe899b80) = -1 EINVAL (Invalid argument)
这会在我的代码中引起问题,因为如果我在其他链接库甚至我自己的代码中进行了某些更改,它将导致此SPI传递函数停止工作。这超出了我的C / C ++代码如何与linux OS交互的知识,因此不胜感激。
不知道这是否与C相关或与Linux内核有关。我正在使用Beaglebone的SPI库BlackLib,它具有SPI传输功能。由于某些原因,它无法正常工作...
memset
和memcpy
也可能无法保证。由于ioctl
结构在某些成员中包含不正确的值,因此package
调用返回错误。