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NAMEown own_send_command own_commmand_wait own_self_command own_acquire_bus own crc own_release_bus OWN_ACQUIRE_BUS OWN_CRC OWN_RELEASE_BUS OWN_SEND_COMMAND - Dallas Semiconductor 1-Wire Network and Transport Interface
SYNOPSISIn sys/bus.h In dev/ow/own.h Ft int Fn own_send_command device_t pdev struct ow_cmd *cmd Ft int Fn own_command_wait device_t pdev struct ow_cmd *cmd Ft int Fn own_self_command device_t pdev struct ow_cmd *cmd uint8_t xpt_cmd Ft int Fn own_acquire_bus device_t pdev int how Ft int Fn own_release_bus device_t pdev Ft int Fn own_crc device_t pdev uint8_t *buffer size_t len Ft int Fn OWN_SEND_COMMAND device_t ndev device_t pdev struct ow_cmd *cmd Ft int Fn OWN_ACQUIRE_BUS device_t ndev device_t pdev int how Ft void Fn OWN_RELEASE_BUS device_t ndev device_t pdev Ft uint8_t Fn OWN_CRC device_t ndev device_t pdev uint8_t *buffer size_t len
DESCRIPTIONThe interface defines three sets of functions for interacting with 1-Wire devices: sending commands, reserving the bus, and ensuring data integrity. Wrappers are provided for the raw OWN kobj(9) interfaces and should be used for improved safety over the kobj(9) ones.
Bus CommandsThe 1-Wire bus defines different layers of access to the devices on the bus. The functions provide access to the network and transport layers. The network layer designates the next command as being either for all devices on the bus, or for a specific device. The network layer also specifies the speed used by the link layer.
Vt struct ow_cmd encapsulates network access, speed, and timing information. It specifies the commands to send and whether or not to read data. Its members are:
Flags controlling the interpretation of the structure.
These flags are defined in
In dev/ow/ow.h :
- Send xpt_cmd bytes and read xpt_read bytes at overdrive speed.
- Interpret xpt_read_len to be in bits to be read after xpt_cmd rather than bytes.
- ROM command bytes to send.
- Number of ROM command bytes to send.
- Number of bytes to read after sending the ROM command.
- Buffer for bytes read after the ROM command.
- Transport command to send.
- Length of the transport command bytes to send. Specify 0 for no transport command.
- Number of bytes to read after xpt_cmd bytes are sent. If the OW_FLAG_READ_BIT bit is set in flags then it is the number of bits to read. Bits read are packed into bytes.
- Buffer for data read.
Fn own_command_wait acquires the 1-Wire bus, waiting if necessary, sends the command, and then releases the bus. Fn own_send_command sends the command without bus reservation. Fa pdev is the client device (the presentation layer device) sending the command. The Fa cmd argument describes the transaction to send to the 1-Wire bus.
Fn own_self_command fills in Fa cmd with a MATCH_ROM ROM command, the ROM address of Fa pdev and the Fa xpt_cmd as a convenient way to create directed commands.
Bus ReservationThe 1-Wire system includes an advisory lock for the bus that presentation layer devices can use to coordinate access. Locking is purely advisory at this time.
Fn own_acquire_bus reserves the bus. It waits indefinitely if the Fa how argument is OWN_WAIT and returns the error EWOULDBLOCK if passed OWN_DONTWAIT when the bus is owned by another client.
Fn own_release_bus releases the bus.
Data IntegrityFn own_crc computes the 1-Wire standard CRC function over the data passed in Fa buffer and Fa len and returns the result.
NotesThe 1-Wire standard (Maxim AN937) defines layers that are akin to ISO networking layers. The lowest relevant layer, the link layer, defines the polling windows and the timing of the signaling of different modes. The network layer is built on top of the link layer and is used to address devices in a unicast or multicast manner. The transport layer defines commands and responses from the devices. The presentation layer is composed of the device specific commands and actions used to control the specific 1-Wire devices on bus.
These interfaces are implemented by the ow(4) device. Presentation layer devices (children of the newbus ow(4) device) should only call the functions described here. The functionality provided by the owc(4) device (specifically the owll(9) interface) should only be called by the ow(4) driver.