DMA_Slot Class Reference

#include <dma_slot.h>

Collaboration diagram for DMA_Slot:


Public Member Functions
	DMA_Slot ()
void	deny_use ()
void	allow_use ()
void	detach_camera ()
void	attach_camera (Mr1394_Hw_Camera *pcam_ptr, float bandwidth)
Static Public Member Functions
static float	get_available_isochronous_bus_bandwidth ()
static DMA_Slot *	wait_for_dma_slot ()
Static Public Attributes
static const int	DMA_SLOT_COUNT = 4
Private Attributes
Mr1394_Hw_Camera *	_pcam_ptr
float	_bandwidth
bool	_allow_usage
Classes
class	DMA_Resource_Guard

Detailed Description

Definition at line 3 of file dma_slot.h.

Constructor & Destructor Documentation

DMA_Slot::DMA_Slot ( )

Definition at line 53 of file dma_slot.cc.

00054   : _pcam_ptr(NULL),
00055     _bandwidth(0.0),
00056     _allow_usage(true)
00057 { }

Member Function Documentation

float DMA_Slot::get_available_isochronous_bus_bandwidth ( ) [static]

Definition at line 66 of file dma_slot.cc.

References global_available_bandwidth.

00067 {
00068   return global_available_bandwidth;
00069 }

DMA_Slot * DMA_Slot::wait_for_dma_slot ( ) [static]

Definition at line 161 of file dma_slot.cc.

References _allow_usage, _pcam_ptr, detach_camera(), dma_slot, DMA_SLOT_COUNT, global_available_slot_counting_sem(), global_next_dma_slot, Mr1394_Hw_Camera::lock(), and Mr1394_Hw_Camera::unlock().

Referenced by grab_all_resources().

00162 {
00163   // Wait for a slot to become available.
00164   global_available_slot_counting_sem.acquire();
00165 
00166   // We know there is an available slot.  Find it.
00167   int j = global_next_dma_slot;
00168   do {
00169     if (dma_slot[j]._allow_usage) {
00170       Mr1394_Hw_Camera* pcam_ptr = dma_slot[j]._pcam_ptr;
00171       if (pcam_ptr != NULL) {
00172         // dma_slot is available ==> its camera will be unlocked.
00173         // Consequently, pcam_ptr->lock() will not block.
00174         pcam_ptr->lock();
00175         dma_slot[j].detach_camera();
00176         pcam_ptr->unlock();
00177       }
00178       dma_slot[j]._allow_usage = false;
00179       ++global_next_dma_slot;
00180       if (global_next_dma_slot >= DMA_SLOT_COUNT) global_next_dma_slot = 0;
00181       return &dma_slot[j];
00182     }
00183     ++j;
00184     if (j >= DMA_SLOT_COUNT) j = 0;
00185   } while (j != global_next_dma_slot);
00186   assert(false);
00187   return NULL;
00188 }

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void DMA_Slot::deny_use ( )

Definition at line 81 of file dma_slot.cc.

References _allow_usage, and global_available_slot_counting_sem().

Referenced by grab_all_resources().

00082 {
00083   if (_allow_usage) {
00084     // This DMA slot is not use exclusively, so the following acquire
00085     // should not block.
00086     global_available_slot_counting_sem.acquire();
00087     _allow_usage = false;
00088   }
00089 }

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void DMA_Slot::allow_use ( )

Definition at line 103 of file dma_slot.cc.

References _allow_usage, and global_available_slot_counting_sem().

Referenced by Mr1394_Camera::~Mr1394_Camera().

00104 {
00105   if (!_allow_usage) {
00106     _allow_usage = true;
00107     global_available_slot_counting_sem.release();
00108   }
00109 }

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void DMA_Slot::detach_camera ( )

Definition at line 118 of file dma_slot.cc.

References _bandwidth, _pcam_ptr, Mr1394_Hw_Camera::dma_slot_ptr, global_available_bandwidth, and Mr1394_Hw_Camera::to_unready_state().

Referenced by wait_for_dma_slot(), and Mr1394_Camera::~Mr1394_Camera().

00119 {
00120   if (_pcam_ptr != NULL) {
00121     _pcam_ptr->to_unready_state();
00122     global_available_bandwidth += _bandwidth;
00123     _bandwidth = 0.0;
00124     _pcam_ptr->dma_slot_ptr = NULL;
00125     _pcam_ptr = NULL;
00126   }
00127 }

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void DMA_Slot::attach_camera	(	Mr1394_Hw_Camera *	pcam_ptr,
		float	bandwidth
	)

Definition at line 141 of file dma_slot.cc.

References _bandwidth, _pcam_ptr, Mr1394_Hw_Camera::dma_slot_ptr, and global_available_bandwidth.

Referenced by dma_slot_attach_camera().

00142 {
00143   // dma_slot may already be active
00144   assert(_pcam_ptr == NULL || _pcam_ptr == pcam_ptr);
00145   _pcam_ptr = pcam_ptr;
00146   _pcam_ptr->dma_slot_ptr = this;
00147   global_available_bandwidth += _bandwidth;
00148   _bandwidth = bandwidth;
00149   global_available_bandwidth -= _bandwidth;
00150 }