Hello,

I have a project, where I have to write a driver for /dev/spidev0.0, but I have problems with fpioctl.

I believe that I have problems with the parameter passing or type casting of fpioctl.
In some forums, I've found mysterios Pointer(PtrInt(xx) syntax like that: fpioctl(fd,funcnum, Pointer(PtrInt(xy)) :
I have no idea why this construction is necesary

My code snipet is below:

spi_ioc_transfer_t = record
    tx_buf_ptr   : pointer;
    rx_buf_ptr   : pointer;
    len    : longword;
    delay_usec  : word;
    speed_hz     : longword;
    bits_per_word : byte;
    cs_change  : byte;
    pad    : longword;
  end;
var xfer : array[0..1] of spi_ioc_transfer_t; rx0,tx0 : array[0..42] of
byte;
tx0 [ 0]:=$00; tx0 [ 1]:=$00;
xfer[0].len:=2; xfer[0].speed_hz:=500000; xfer[0].bits_per_word:=8;
xfer[0].tx_buf_ptr := addr(tx0[ 0]); xfer[0].rx_buf_ptr := addr(rx0[
0]);
fd:=fpOpen('/dev/spidev0.0',O_RdWr);
...
result := fpioctl(fd, (*SPI_IOC_MESSAGE(1)*) 1075866368, @xfer[0]);
(* function number 107.. 368 taken from operating c example *)

I get -1 as result
What's wrong.

Stefan Fischer wrote on Tue, 19 Jun 2012:

The speed_hz and delay_usec fields are switched around. Furthermore, make sure to add add {$packrecords C} to guarantee the same alignment as in a C compiler.

Jonas

Also, the buffers need to be u64. Is the pointer type in pascal always 64 bit?

Henry

Henry Vermaak wrote on Tue, 19 Jun 2012:

Also, the buffers need to be u64. Is the pointer type in pascal always 64 bit?

u64 is defined as "unsigned long". "unsigned long" is the same size as a pointer on Linux.

Jonas

I've changed to following:
added packrecord c
flipped speed_hz and delay_usec fields

same problem.
I don't know whats really wrong.
Is there any debug possibility?

Have you tried looking at errno? Do any of the other ioctls succeed (e.g. SPI_IOC_WR_MAX_SPEED_HZ)? Do you have permissions to write to this file?

Henry

Henry Vermaak wrote

Have you tried looking at errno?  Do any of the other ioctls succeed

Sorry, errno -> GetLastOSError()

Henry

Are you sure about the conversion (*SPI_IOC_MESSAGE(1)*) 1075866368? That is 40206B00 hex. 6B is the letter 'k' SPI_IOC_MAGIC but the 20 seems to indicate a size of 32 bytes while the record has only a size of 24 bytes on ARM (32 bit pointers). Also the 40 seems to be wrong as it corresponds to IOC_IN.

#define SPI_MSGSIZE(N) \
((((N)*(sizeof (struct spi_ioc_transfer))) < (1 << _IOC_SIZEBITS)) \ ? ((N)*(sizeof (struct spi_ioc_transfer))) : 0)
#define SPI_IOC_MESSAGE(N) _IOW(SPI_IOC_MAGIC, 0, char[SPI_MSGSIZE(N)]) #define _IOW(g,n,t) _IOC(IOC_IN, (g), (n), sizeof(t)) #define _IOC(inout,group,num,len) \
((unsigned long)(inout | ((len & IOCPARM_MASK) << 16) | ((group) <<
8) | (num)))
#define _IOR(g,n,t) _IOC(IOC_OUT, (g), (n), sizeof(t)) #define IOC_OUT 0x40000000 /* copy out parameters */ #define IOC_IN 0x80000000

Ludo

Ludo Brands wrote

Are you sure about the conversion (*SPI_IOC_MESSAGE(1)*) 1075866368? That is

I can confirm that a c program spits out this number for SPI_IOC_MESSAGE(1).

Henry

And what is sizeof (struct spi_ioc_transfer) in c? Because that would indicate that u64 needs to be indeed 64 bits. I have seen u64 defined as typedef unsigned long long for ARM.

Ludo

Ludo Brands wrote

And what is sizeof (struct spi_ioc_transfer) in c?

32.

Because that would indicate that u64 needs to be indeed 64 bits. I have seen u64 defined as typedef unsigned long long for ARM.

"long" is 32 bits on my arm laptop, so that makes sense.

Henry

So the struct should be translated as

spi_ioc_transfer_t = record
    tx_buf_ptr   : qword;
    rx_buf_ptr   : qword;
    len    : longword;
    speed_hz     : longword;
    delay_usec  : word;
    bits_per_word : byte;
    cs_change  : byte;
    pad    : longword;
  end;

Ludo

Yes, or use ctypes to make it more clear.

Henry

after some experiments, tx.. and rx_buf_ptr has to be 64 bits. On fps on arm, the pointer type is translated to 32 Bits. Ludo's suggestions to use qword (64Bit) is correct.

Is there a possibility to use pointer type with 64 Bits? How ?

spi_ioc_transfer_t = record
    tx_buf_ptr,dummytx    : pointer;     (* <------------ 64 Bits              dummytx / dummyrx for spaceing *)
    rx_buf_ptr,dummyrx 	: pointer;
    len				: longword;
	speed_hz    	: longword;
    delay_usecs		: word;
    bits_per_word	: byte;
    cs_change		: byte;
    pad				: longword;
  end;

Henry Vermaak wrote

Also, the buffers need to be u64.  Is the pointer type in pascal always 64 bit?

The answer to this is no, so you can't use pascal pointer types for the buffers.

Henry

I wouldn't do that. The kernel could use the part that you labeled as "dummy*x". Just simply cast a Pointer to QWord and be happy. As long as we don't have a 128-bit system this will work ;) (and C basically does the same)

Regards,
Sven