blk_queue_make_request(9) [suse man page]

BLK_QUEUE_MAKE_REQUE(9) 					   Block Devices					   BLK_QUEUE_MAKE_REQUE(9)

NAME

       blk_queue_make_request - define an alternate make_request function for a device

SYNOPSIS

       void blk_queue_make_request(struct request_queue * q, make_request_fn * mfn);

ARGUMENTS

       q
	   the request queue for the device to be affected

       mfn
	   the alternate make_request function

DESCRIPTION

       The normal way for struct bios to be passed to a device driver is for them to be collected into requests on a request queue, and then to
       allow the device driver to select requests off that queue when it is ready. This works well for many block devices. However some block
       devices (typically virtual devices such as md or lvm) do not benefit from the processing on the request queue, and are served best by
       having the requests passed directly to them. This can be achieved by providing a function to blk_queue_make_request.

CAVEAT

       The driver that does this *must* be able to deal appropriately with buffers in "highmemory". This can be accomplished by either calling
       __bio_kmap_atomic to get a temporary kernel mapping, or by calling blk_queue_bounce to create a buffer in normal memory.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						   BLK_QUEUE_MAKE_REQUE(9)

STRUCT 
SPI_MASTER(9)					  Serial Peripheral Interface (S				      STRUCT SPI_MASTER(9)

NAME

       struct_spi_master - interface to SPI master controller

SYNOPSIS

       struct spi_master {
	 struct device dev;
	 s16 bus_num;
	 u16 num_chipselect;
	 u16 dma_alignment;
	 u16 mode_bits;
	 u16 flags;
       #define SPI_MASTER_HALF_DUPLEX	  BIT(0)
       #define SPI_MASTER_NO_RX BIT(1)
       #define SPI_MASTER_NO_TX BIT(2)
	 int (* setup) (struct spi_device *spi);
	 int (* transfer) (struct spi_device *spi,struct spi_message *mesg);
	 void (* cleanup) (struct spi_device *spi);
       };

MEMBERS

       dev
	   device interface to this driver

       bus_num
	   board-specific (and often SOC-specific) identifier for a given SPI controller.

       num_chipselect
	   chipselects are used to distinguish individual SPI slaves, and are numbered from zero to num_chipselects. each slave has a chipselect
	   signal, but it's common that not every chipselect is connected to a slave.

       dma_alignment
	   SPI controller constraint on DMA buffers alignment.

       mode_bits
	   flags understood by this controller driver

       flags
	   other constraints relevant to this driver

       setup
	   updates the device mode and clocking records used by a device's SPI controller; protocol code may call this. This must fail if an
	   unrecognized or unsupported mode is requested. It's always safe to call this unless transfers are pending on the device whose settings
	   are being modified.

       transfer
	   adds a message to the controller's transfer queue.

       cleanup
	   frees controller-specific state

DESCRIPTION

       Each SPI master controller can communicate with one or more spi_device children. These make a small bus, sharing MOSI, MISO and SCK signals
       but not chip select signals. Each device may be configured to use a different clock rate, since those shared signals are ignored unless the
       chip is selected.

       The driver for an SPI controller manages access to those devices through a queue of spi_message transactions, copying data between CPU
       memory and an SPI slave device. For each such message it queues, it calls the message's completion function when the transaction completes.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010						      STRUCT SPI_MASTER(9)