Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #193
Difficulty: Easy
Python was selected the Programming Language of the Year in 2007, 2010, and 2018.
True or False?
Linux & Unix Commands - Search Man Pages

spi_alloc_master(9) [centos man page]

SPI_ALLOC_MASTER(9)					  Serial Peripheral Interface (S				       SPI_ALLOC_MASTER(9)

NAME
spi_alloc_master - allocate SPI master controller SYNOPSIS
struct spi_master * spi_alloc_master(struct device * dev, unsigned size); ARGUMENTS
dev the controller, possibly using the platform_bus size how much zeroed driver-private data to allocate; the pointer to this memory is in the driver_data field of the returned device, accessible with spi_master_get_devdata. CONTEXT
can sleep DESCRIPTION
This call is used only by SPI master controller drivers, which are the only ones directly touching chip registers. It's how they allocate an spi_master structure, prior to calling spi_register_master. This must be called from context that can sleep. It returns the SPI master structure on success, else NULL. The caller is responsible for assigning the bus number and initializing the master's methods before calling spi_register_master; and (after errors adding the device) calling spi_master_put and kfree to prevent a memory leak. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 SPI_ALLOC_MASTER(9)

Check Out this Related Man Page

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; struct list_head list; s16 bus_num; u16 num_chipselect; u16 dma_alignment; u16 mode_bits; u32 bits_per_word_mask; u16 flags; #define SPI_MASTER_HALF_DUPLEX BIT(0) #define SPI_MASTER_NO_RX BIT(1) #define SPI_MASTER_NO_TX BIT(2) spinlock_t bus_lock_spinlock; struct mutex bus_lock_mutex; bool bus_lock_flag; int (* setup) (struct spi_device *spi); int (* transfer) (struct spi_device *spi,struct spi_message *mesg); void (* cleanup) (struct spi_device *spi); bool queued; struct kthread_worker kworker; struct task_struct * kworker_task; struct kthread_work pump_messages; spinlock_t queue_lock; struct list_head queue; struct spi_message * cur_msg; bool busy; bool running; bool rt; int (* prepare_transfer_hardware) (struct spi_master *master); int (* transfer_one_message) (struct spi_master *master,struct spi_message *mesg); int (* unprepare_transfer_hardware) (struct spi_master *master); int * cs_gpios; }; MEMBERS
dev device interface to this driver list link with the global spi_master list 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 bits_per_word_mask A mask indicating which values of bits_per_word are supported by the driver. Bit n indicates that a bits_per_word n+1 is suported. If set, the SPI core will reject any transfer with an unsupported bits_per_word. If not set, this value is simply ignored, and it's up to the individual driver to perform any validation. flags other constraints relevant to this driver bus_lock_spinlock spinlock for SPI bus locking bus_lock_mutex mutex for SPI bus locking bus_lock_flag indicates that the SPI bus is locked for exclusive use 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 queued whether this master is providing an internal message queue kworker thread struct for message pump kworker_task pointer to task for message pump kworker thread pump_messages work struct for scheduling work to the message pump queue_lock spinlock to syncronise access to message queue queue message queue cur_msg the currently in-flight message busy message pump is busy running message pump is running rt whether this queue is set to run as a realtime task prepare_transfer_hardware a message will soon arrive from the queue so the subsystem requests the driver to prepare the transfer hardware by issuing this call transfer_one_message the subsystem calls the driver to transfer a single message while queuing transfers that arrive in the meantime. When the driver is finished with this message, it must call spi_finalize_current_message so the subsystem can issue the next transfer unprepare_transfer_hardware there are currently no more messages on the queue so the subsystem notifies the driver that it may relax the hardware by issuing this call cs_gpios Array of GPIOs to use as chip select lines; one per CS number. Any individual value may be -ENOENT for CS lines that are not GPIOs (driven by the SPI controller itself). 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 3.10 June 2014 STRUCT SPI_MASTER(9)

Featured Tech Videos