Linux kernel about SPI device Tree parameter resolution

• Recently made an SPI device driver upgrade from board-level device driver to device-tree device driver, which needs to understand the parsing of the SPI Device tree code.
• The device tree is configured as follows:

  503&spi0 {504Status ="Okay";505Pinctrl-name ="Default";506Pinctrl-0= <&spi0_pins>;507ti,pindir-d0-out-d1-in;508509wk2124a {510Compatible ="wk2124a";//Match string511Reg = <0>;//CS +# Spi-cpha = <1>;//Configure the SPI mode513# Spi-tx-bus-width = <1>;//This is the bus width of the spi-tx514# Spi-rx-bus-width = <1>;515Spi-max-frequency = <10000000>;//SPI max rate configuration516};517};

• Code tracking

  //Drivers/spi/spi.c2772Postcore_initcall (Spi_init);2733 Static int__init Spi_init (void)2734{2735     intStatus27362737BUF = Kmalloc (Spi_bufsiz, Gfp_kernel);2738     if(!BUF) {2739status =-enomem;2740         GotoErr0;2741}27422743Status = Bus_register (&spi_bus_type);2744     if(Status <0)2745         GotoERR1;27462747Status = Class_register (&spi_master_class);2748     if(Status <0)2749         GotoERR2;27502751     if(is_enabled (config_of_dynamic))2752Warn_on (Of_reconfig_notifier_register (&spi_of_notifier));27532754     return 0;27552756ERR2:2757Bus_unregister (&spi_bus_type);2758ERR1:2759Kfree (BUF);2760BUF = NULL;2761ERR0:2762     returnStatus2763}2726 Static structNotifier_block Spi_of_notifier = {2727. Notifier_call = Of_spi_notify,2728};2686 Static intOf_spi_notify (structNotifier_block *NB,unsigned LongAction2687              void*ARG)2688{2689     structOf_reconfig_data *rd = arg;2690     structSpi_master *master;2691     structSpi_device *spi;26922693     Switch(Of_reconfig_get_state_change (Action, ARG)) {2694      CaseOf_reconfig_change_add:2695master = Of_find_spi_master_by_node (rd->dn->parent);2696         if(Master = = NULL)2697             returnNOTIFY_OK;/* Not for US * /26982699SPI = Of_register_spi_device (master, RD-&GT;DN);//---> Registration equipment2700Put_device (&master->dev);// ... ... 27222723     returnNOTIFY_OK;2724}1428#if defined (config_of)1429 Static structSpi_device *1430Of_register_spi_device (structSpi_master *master,structDevice_node *NC)1431{1432     structSpi_device *spi;1433     intRc1434U32 value;14351436     / * Alloc an spi_device * /1437SPI = Spi_alloc_device (master);1438     if(!SPI) {1439Dev_err (&master->dev,"Spi_device alloc error for%s\ n",1440Nc->full_name);1441rc =-enomem;1442         GotoErr_out;1443}14441445     / * Select Device driver * /1446rc = Of_modalias_node (NC, Spi->modalias,1447                 sizeof(Spi->modalias));1448     if(RC <0) {1449Dev_err (&master->dev,"Cannot find Modalias for%s\ n",1450Nc->full_name);1451         GotoErr_out;1452}14531454     / * Device address * /1455rc = Of_property_read_u32 (NC,"Reg", &value);1456     if(RC) {1457Dev_err (&master->dev,"%s have no valid ' Reg ' property (%d)\ n",1458Nc->full_name, RC);1459         GotoErr_out;1460}1461Spi->chip_select = value;14621463     /* Mode (Clock phase/polarity/etc.) */1464     if(Of_find_property (NC,"Spi-cpha", NULL))1465Spi->mode |= Spi_cpha;1466     if(Of_find_property (NC,"Spi-cpol", NULL))1467Spi->mode |= Spi_cpol;1468     if(Of_find_property (NC,"Spi-cs-high", NULL))1469Spi->mode |= Spi_cs_high;1470     if(Of_find_property (NC,"Spi-3wire", NULL))1471Spi->mode |= Spi_3wire;1472     if(Of_find_property (NC,"Spi-lsb-first", NULL))1473Spi->mode |= Spi_lsb_first;14741475     / * Device dual/quad mode * /1476     if(!of_property_read_u32 (NC,"Spi-tx-bus-width", &value)) {1477         Switch(value) {1478          Case 1:1479              Break;1480          Case 2:1481Spi->mode |= spi_tx_dual;1482              Break;1483          Case 4:1484Spi->mode |= Spi_tx_quad;1485              Break;1486         default:1487Dev_warn (&master->dev,1488                 "Spi-tx-bus-width%d not supported\ n",1489Value);1490              Break;1491}1492}14931494     if(!of_property_read_u32 (NC,"Spi-rx-bus-width", &value)) {1495         Switch(value) {1496          Case 1:1497              Break;1498          Case 2:1499Spi->mode |= spi_rx_dual; the              Break;1501          Case 4:1502Spi->mode |= Spi_rx_quad;1503              Break;1504         default:1505Dev_warn (&master->dev,1506                 "Spi-rx-bus-width%d not supported\ n",1507Value);1508              Break;1509}1510}15111512     / * Device speed * /1513rc = Of_property_read_u32 (NC,"Spi-max-frequency", &value);1514     if(RC) {1515Dev_err (&master->dev,"%s have no valid ' spi-max-frequency ' property (%d)\ n",1516Nc->full_name, RC);1517         GotoErr_out;1518}1519Spi->max_speed_hz = value;15201521     / * Store A pointer to the node in the device structure * /1522Of_node_get (NC);1523Spi->dev.of_node = NC;15241525     / * Register the new device * /1526rc = Spi_add_device (SPI);1527     if(RC) {1528Dev_err (&master->dev,"Spi_device Register error%s\ n",1529Nc->full_name);1530         GotoErr_out;1531}15321533     returnSpi15341535Err_out:1536Spi_dev_put (SPI);1537     returnErr_ptr (RC);1538}

Linux kernel about SPI device Tree parameter resolution