SPI_NBITS_SINGLE ?

I am looking for better explanation what tx_nbits and rx_nbits do.
Perhaps they are talking about "bytes"?

tx_nbits
number of bits used for writing. If 0 the default (SPI_NBITS_SINGLE) is used.
rx_nbits
number of bits used for reading. If 0 the default (SPI_N






struct spi_transfer {
const void * tx_buf;
void * rx_buf;
unsigned len;
dma_addr_t tx_dma;
dma_addr_t rx_dma;
struct sg_table tx_sg;
struct sg_table rx_sg;
unsigned cs_change:1;
unsigned tx_nbits:3;
unsigned rx_nbits:3;
#define SPI_NBITS_SINGLE 0x01
#define SPI_NBITS_DUAL 0x02
#define SPI_NBITS_QUAD 0x04
u8 bits_per_word;
u16 delay_usecs;
u32 speed_hz;
struct list_head transfer_list;
};


FYI here is a link to ONE of few copies of SAME article on the web

https://manpages.debian.org/wheezy-b...sfer.9.en.html

No. The :3 declares a member that is 3 bits wide. http://en.cppreference.com/w/c/language/bit_field

Maybe the following will help. From here: https://github.com/torvalds/linux/bl...spi/spi.h#L765

Thanks
You made a reference to resource I have been using.

" When SPI can transfer (what ?) in 1x,2x or 4x" - seems incomplete sentence.
Transfer in ...what ?

Any data in "small parts" - not a whole 8 bit word at once - as configured elsewhere?

Which member of the struct are they talking about?
The #defines are 1,2,4 and the value for x_nbits is 3

No, I still do not get it, sorry.

1x is 1, 2x is 2, and 4x is 3.