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VCLinux Library Documentation
3.13.0
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VCLinux Library Documentation
3.13.0
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These functions provide allocation and handling of contiguous memory needed for FPGA Operations like memory for images written by the sensor, etc. Cause is, in difference to our TI DSP based cameras, the memory handling at the ARM platform over a memory management unit (MMU). More...
Collaboration diagram for Contiguous Memory:Functions | |
| I32 | vc_memctg_init (I32 *fdMem, char *memCtgDev) |
| Opens the VCMemCtg Device for Memory Allocations. More... | |
| I32 | vc_memctg_deinit (I32 *fdMem) |
| Closes the VCMemCtg Device for Memory Allocations. More... | |
| I32 | vc_memctg_baseinfo (U8 **zeroAddr, U32 *totalBytes, I32 fdMem) |
| Overall Contiguous Memory Information over the VCMemCtg Device. More... | |
| I32 | vc_memctg_alloc (U8 **ptr, U32 requestByteSize, U32 *allocatedByteSize, I32 fdMem) |
| Allocates Contiguous Memory over the VCMemCtg Device. More... | |
| I32 | vc_memctg_free (U8 **ptr, U32 requestByteSize, I32 fdMem) |
| Frees Contiguous Memory over the VCMemCtg Device. More... | |
| I32 | vc_memctg_invalidate (U8 *ptr, U32 requestByteSize, I32 fdMem) |
| Invalidate Contiguous Memory over the VCMemCtg Device. More... | |
| I32 | vc_memctg_flush (U8 *ptr, U32 requestByteSize, I32 fdMem) |
| Flushes Cache Data to Contiguous Memory over the VCMemCtg Device. More... | |
| I32 | vc_memctg_containment_check (U8 *stPtr, U32 byteCount, I32 fdMem) |
| Checks if Pointer and Range lies fully in the Contiguous Memory Area. More... | |
| I32 | vc_memctg_map (U8 toDeviceIff1, U8 *ptr, U32 requestByteSize, I32 fdMem) |
| Map Contiguous Memory to Hardware over the VCMemCtg Device. More... | |
On a positive note is the controlled termination of a program by a so-called segmentation fault if memory access is undefined, e.g. if one accesses an array element over an index which is out of bounds; and the ability to allocate large blocks in a fragmented memory. On a negative note is the overhead of sharing memory between independent processes and the not-guaranteed physically contiguous memory.
The image visualizes two behaviours of the MMU:
The first mentioned behaviour is bad for transferring image data from the sensor to the user accessible memory, since the FPGA Hardware needs one contiguous block of memory. So you have to use the address pointers initialized, for example, by the vc_capt_init() routine for image acquisition since they point to contiguously allocated memory. The second mentioned behaviour is important for sharing memory between, for example, the image transfer server and the image processing program. By using the address returned by vc_imgnet_attach(), you use memory which can be accessed by both, the image transfer server and your program, at any time, since it is declared as shared memory. Note, that shared memory for inter-process-communication does not need to be contiguous!
This function opens the VCMem Device for Memory Allocations.
| memCtgDev | You may use the default define VCMemDev_Default. |
This function returns the total contiguous memory area and the byte size over the VCMemCtg device.
This function allocates contiguous memory over the VCMemCtg device. Due to its behaviour, the size is rounded to the next memory manager block size.
This function frees contiguous memory over the VCMemCtg device.
This function invalidates contiguous memory over the VCMemCtg device.
This function flushes cache data to contiguous memory over the VCMemCtg device.
This function checks, if a given pointer and range lies fully in the contiguous memory area. However it does not check the Allocation state, or the membership to a specific block.
