49 lines
1.2 KiB
C
49 lines
1.2 KiB
C
/* Peek and poke using /dev/mem.
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*
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* Callers now ought to check the return values.
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*
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* Calling peek() requires read permission on /dev/mem, and consumes
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* a file descriptor. Calling poke() requires write permission, and
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* consumes another file descriptor.
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*/
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#include <sys/types.h>
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#include <fcntl.h>
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#include <unistd.h>
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_PROTOTYPE( int peek, (unsigned segment, unsigned offset));
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_PROTOTYPE( int poke, (unsigned segment, unsigned offset, unsigned value));
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#define SEGSIZE 0x10
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int peek(segment, offset)
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unsigned segment;
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unsigned offset;
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{
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unsigned char chvalue;
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static int infd = -1;
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if (infd < 0) infd = open("/dev/mem", O_RDONLY);
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if (infd < 0 ||
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lseek(infd, (unsigned long) segment * SEGSIZE + offset, SEEK_SET) < 0 ||
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read(infd, (char *) &chvalue, (unsigned) 1) != 1)
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return(-1);
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return(chvalue);
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}
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int poke(segment, offset, value)
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unsigned segment;
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unsigned offset;
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unsigned value;
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{
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unsigned char chvalue;
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static int outfd = -1;
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chvalue = value;
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if (outfd < 0) outfd = open("/dev/mem", O_WRONLY);
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if (outfd < 0 ||
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lseek(outfd, (unsigned long) segment * SEGSIZE + offset, SEEK_SET) < 0 ||
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write(outfd, (char *) &chvalue, (unsigned) 1) != 1)
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return(-1);
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return(chvalue);
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}
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