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[spi] Add address-length autodetection to the SPI bit-bashing code

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Several SPI chips will respond to an SPI read command with a dummy
zero bit immediately prior to the first real data bit.  This can be
used to autodetect the address length, provided that the command
length and data length are already known, and that the MISO data line
is tied high.

Tested-by: Thomas Miletich <thomas.miletich@gmail.com>
Debugged-by: Thomas Miletich <thomas.miletich@gmail.com>
This commit is contained in:
Michael Brown
2009-05-28 14:45:32 +01:00
parent 8afafb6532
commit 92a9978b44
4 changed files with 95 additions and 18 deletions
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8
src/include/gpxe/spi.h
View File

@@ -104,6 +104,14 @@ struct spi_device {
unsigned int munge_address : 1;
};
/**
* SPI magic autodetection address length
*
* Set @c spi_device::address_len to @c SPI_AUTODETECT_ADDRESS_LEN if
* the address length should be autodetected.
*/
#define SPI_AUTODETECT_ADDRESS_LEN 0
static inline __attribute__ (( always_inline )) struct spi_device *
nvs_to_spi ( struct nvs_device *nvs ) {
return container_of ( nvs, struct spi_device, nvs );

1
src/include/gpxe/threewire.h
View File

@@ -45,6 +45,7 @@ extern int threewire_read ( struct nvs_device *nvs, unsigned int address,
void *data, size_t len );
extern int threewire_write ( struct nvs_device *nvs, unsigned int address,
const void *data, size_t len );
extern int threewire_detect_address_len ( struct spi_device *device );
/**
* @defgroup tdevs Three-wire device types