[ECOS] bugs on spi API

["liang rainti" <rainti_1212 at hotmail dot com>]

hi,all,
 i am writing a qspi drivers on mcf5272 for eCos, the qspi has a 
character:read and write in a transfer at one time. Referering generic SPI 
API, cyg_spi_transfer( ) function can read  spi device a transfer at one 
time or write that. But read operation and write operation can not be 
finished at the same time in the transfer( ) function.

eg.
A typical transaction might involve the following. First a command
should be sent to the device, consisting of four bytes. The device
will then respond with a single status byte, zero for failure,
non-zero for success. If successful then the device can accept another
n bytes of data, and will generate a 2-byte response including a
checksum. The device's chip select should remain asserted throughout.
The code for this would look something like:

#include <cyg/io/spi.h>
#include <cyg/hal/hal_io.h>    // Defines the SPI devices

   cyg_spi_transaction_begin(hal_spi_eprom);
   // Interrupt-driven transfer, four bytes of command
  !!! cyg_spi_transaction_transfer(hal_spi_eprom, 0, 4, command, NULL, 0);
   // Read back the status
  !!! cyg_spi_transaction_transfer(hal_spi_eprom, 0, 1, NULL, status, 0);
   
Why not be 
cyg_spi_transaction_transfer(hal_spi_eprom,0,4,command,status,0)???  This 
will be OK??? I am wondering.
  if (!status[0]) {
       // Command failed, generate some extra ticks to drop the chip 
select
       cyg_spi_transaction_tick(hal_spi_eprom, 0, 1);
   } else {
       // Transfer the data, then read back the final status. The
       // chip select should be dropped at the end of this.
       cyg_spi_transaction_transfer(hal_spi_eprom, 0, n, data, NULL, 0);
       cyg_spi_transaction_transfer(hal_spi_eprom, 0, 2, NULL, status, 1);
       // Code for checking the final status should go here 
   }

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