Q: We are converting our Nubus card to a PCI card, and we need to know how to
implement read-modify-write to lock the PCI target device.
A: Designing PCI Cards and Drivers, which is on the PCI Driver Development
Kit (DDK), explains this as follows:
Atomic Memory Operations
The Driver Services Library provides the following 32-, 16-, and 8-bit atomic
memory operations for use by device drivers.
Boolean CompareAndSwap(long oldValue, long newValue, long *Value);
SInt32 IncrementAtomic( SInt32 *value );
SInt32 DecrementAtomic( SInt32 *value );
SInt32 AddAtomic( SInt32 amount, SInt32 *value );
UInt32 BitAndAtomic( UInt32 mask, UInt32 *value );
UInt32 BitOrAtomic( UInt32 mask, UInt32 *value );
UInt32 BitXorAtomic( UInt32 mask, UInt32 *value );
SInt8 IncrementAtomic8( SInt8 *value );
SInt8 DecrementAtomic8( SInt8 *value );
SInt8 AddAtomic8( SInt32 amount, SInt8 *value );
UInt8 BitAndAtomic8( UInt32 mask, UInt8 *value );
UInt8 BitOrAtomic8( UInt32 mask, UInt8 *value );
UInt8 BitXorAtomic8( UInt32 mask, UInt8 *value );
SInt16 IncrementAtomic16( SInt16 *value );
SInt16 DecrementAtomic16( SInt16 *value );
SInt16 AddAtomic16( SInt32 amount, SInt16 *value );
UInt16 BitAndAtomic16( UInt32 mask, UInt16 *value );
UInt16 BitOrAtomic16( UInt32 mask, UInt16 *value );
UInt16 BitXorAtomic16( UInt32 mask, UInt16 *value );
|
The
atomic routines perform various operations on the memory address specified by
value:
IncrementAtomic increments the value by one and DecrementAtomic decrements it
by one. These functions return the value as it was before the change.AddAtomic adds the specified amount to the value at the specified address and returns the result.BitAndAtomic performs a logical and operation between the bits of the specified mask and the value at the specified address, returning the result. Similarly, BitOrAtomic performs a logical or operation and BitXorAtomic performs a logical XOR operation.- The
CompareAndSwap routine compares the value at the specified address with oldValue. The value of newValue is written to the specified address only if oldValue and the value at the specified address are equal. CompareAndSwap returns true if newValue is written to the specified address; otherwise it returns false. A false return value does not imply that oldValue and the value at the specified address are not equal; it only implies that CompareAndSwap did not write newValue to the specified address.
These routines take logical address pointers and ensure that the operations are
atomic with respect to all devices (for example, other processors, DMA engines)
that participate in the coherency architecture of the Macintosh system.
TestAndSet (UInt32 theBit
UInt8 *theAddress);
TestAndClear (UInt32 theBit
UInt8 *theAddress);
theBit The bit number in the range 0 through 7.
theAddress The address of the byte in which the bit is located.
|
TestAndSet and TestAndClear set and clear a single bit in a byte at a specified
address.
|
