Visible to Intel only — GUID: iga1401397708039
Ixiasoft
Visible to Intel only — GUID: iga1401397708039
Ixiasoft
30.4.1. HAL System Library Support
If your program uses the HAL device driver to access the DMA controller, accessing the device registers directly interferes with the correct behavior of the driver.
The HAL DMA driver provides both ends of the DMA process; the driver registers itself as both a receive channel (alt_dma_rxchan) and a transmit channel (alt_dma_txchan). The Nios® II Software Developer’s Handbook provides complete details of the HAL system library and the usage of DMA devices.
ioctl() Operations
ioctl() operation requests are defined for both the receive and transmit channels, which allows you to control the hardware-dependent aspects of the DMA controller. Two ioctl() functions are defined for the receiver driver and the transmitter driver: alt_dma_rxchan_ioctl() and alt_dma_txchan_ioctl(). The table below lists the available operations. These are valid for both the transmit and receive channels.
Request | Meaning |
---|---|
ALT_DMA_SET_MODE_8 | Transfers data in units of 8 bits. The parameter arg is ignored. |
ALT_DMA_SET_MODE_16 | Transfers data in units of 16 bits. The parameter arg is ignored. |
ALT_DMA_SET_MODE_32 | Transfers data in units of 32 bits. The parameter arg is ignored. |
ALT_DMA_SET_MODE_64 | Transfers data in units of 64 bits. The parameter arg is ignored. |
ALT_DMA_SET_MODE_128 | Transfers data in units of 128 bits. The parameter arg is ignored. |
ALT_DMA_RX_ONLY_ON (1) | Sets a DMA receiver into streaming mode. In this case, data is read continuously from a single location. The parameter arg specifies the address to read from. |
ALT_DMA_RX_ONLY_OFF (1) | Turns off streaming mode for a receive channel. The parameter arg is ignored. |
ALT_DMA_TX_ONLY_ON (1) | Sets a DMA transmitter into streaming mode. In this case, data is written continuously to a single location. The parameter arg specifies the address to write to. |
ALT_DMA_TX_ONLY_OFF (1) | Turns off streaming mode for a transmit channel. The parameter arg is ignored. |
Notes :
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Limitations
Currently the Intel-provided drivers do not support 64-bit and 128-bit DMA transactions.
This function is not thread safe. If you want to access the DMA controller from more than one thread then you should use a semaphore or mutex to ensure that only one thread is executing within this function at any time.