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Describes the interface to the SDMA manager.
The sdma user interface library wraps file system calls to an associated kernel module (sdmak.ko), which needs to be loaded in order for calls to to this library to succeed.
To install sdmak.ko, enter % insmod sdmak.ko on a Linux command line.
SDMA channels are allocated (requested) from within the sdmak kernel driver through the SDMA_getChannels() API. This request is granted by way of the kernel's request_dma() functionality (omap_request_dma() for the OMAP35x), so it will work in conjuntion with independent kernel DMA usage without conflict or custom kernel configuration. The granted channel's registers are memory-mapped into the calling user address space to allow the application to directly access the DMA registers for that channel.
A DMA callback ISR is registered within the stock kernel DMA manager, and this ISR is used for completion notification (although it could be customized to handle any DMA-generated interrupt). Notification to the user interface layer is accomplished by way of a user state structure whose address is passed to the sdmak kernel driver and which is directly written upon completion. Atomic hand-shaking allows the kernel driver to know if the application is going to wait for the completion by way of the corresponding sdmak ioctl(), as opposed to just checking the user state structure, and post a channel-specific mutex only when needed (otherwise just the completion flag in the state structure is set).
Since the SDMA interface library doesn't use the GT tracing facility, there is one configuration option available for the SDMA module to control whether the debug or release interface library is used for building the application. This config parameter is named 'debug' and is of type bool, and the default value is 'false'.
The following line is an example of enabling usage of the debug interface library: var sdma = xdc.useModule('ti.sdo.linuxutils.sdma.SDMA'); sdma.debug = true; This will enable "SDMA Debug" statements to be printed to stdout.
Go to the source code of this file.
Data Structures | |
| struct | SDMA_transferState |
| State structure shared between SDMAK and SDMA user layers. More... | |
| union | SDMA_requestDmaParams |
| SDMAK ioctl input/output parameters. More... | |
| struct | SDMA_ChannelDescriptor |
| Descriptor for a channel granted with a SDMA_IOCREQUESTDMA ioctl(). More... | |
Defines | |
| #define | SDMA_VERSION 0x01010000U |
| #define | SDMA_IOCMAGIC 0x0000fb00 |
| SDMAK ioctl() commands. | |
| #define | SDMA_IOCCMDMASK 0x000000ff |
| #define | SDMA_IOCREQUESTDMA 1 |
| #define | SDMA_IOCRELEASEDMA 2 |
| #define | SDMA_IOCWAITFORCOMPLETION 3 |
| #define | SDMA_IOCGETVERSION 4 |
Typedefs | |
| typedef struct SDMA_ChannelDescriptor | SDMA_ChannelDescriptor |
| Descriptor for a channel granted with a SDMA_IOCREQUESTDMA ioctl(). | |
| typedef enum SDMA_Status | SDMA_Status |
| Status codes for SDMA API return values. | |
Enumerations | |
| enum | SDMA_Status { SDMA_OK = 0, SDMA_EFAIL, SDMA_ENOCHANNEL, SDMA_ENOINIT } |
Status codes for SDMA API return values. More... | |
Functions | |
| int | SDMA_init (void) |
| SDMA initialization API. | |
| int | SDMA_exit (void) |
| SDMA finalization API. | |
| SDMA_Status | SDMA_getChannels (int numChannels, SDMA_ChannelDescriptor chanArray[]) |
| Returns available logical channels. | |
| SDMA_Status | SDMA_freeChannels (int numChannels, SDMA_ChannelDescriptor chanArray[]) |
| Frees previously requested logical channels. | |
| SDMA_Status | SDMA_wait (SDMA_ChannelDescriptor *channel) |
| Waits for the transfer corresponding to this descriptor to complete. | |
| SDMA_Status | SDMA_check (SDMA_ChannelDescriptor *channel, int *pcompleted) |
| Checks the status of the transfer corresponding to this descriptor and returns it in the *pcompleted field. | |
| int | SDMA_getVersion (void) |
| Retrieve version from SDMA driver. | |
