Linux kernel 有关 spi 设备树参数解析

503 &spi0 {
504     status = "okay";
505     pinctrl-name = "default";
506     pinctrl-0 = <&spi0_pins>;
507     ti,pindir-d0-out-d1-in;
508
509     wk2124A {
510         compatible = "wk2124A";    //  匹配字符串
511         reg = <0>;                    // cs 
512         # spi-cpha = <1>;              // 配置 spi  的模式
513         # spi-tx-bus-width = <1>;   // 这是是 spi-tx 的总线宽度
514         # spi-rx-bus-width = <1>;
515         spi-max-frequency = <10000000>;        // spi 最大速率配置
516     };
517 };

// drivers/spi/spi.c
2772 postcore_initcall(spi_init);

2733 static int __init spi_init(void)
2734 {
2735     int status;
2736
2737     buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
2738     if (!buf) {
2739         status = -ENOMEM;
2740         goto err0;
2741     }
2742
2743     status = bus_register(&spi_bus_type);
2744     if (status < 0)
2745         goto err1;
2746
2747     status = class_register(&spi_master_class);
2748     if (status < 0)
2749         goto err2;
2750
2751     if (IS_ENABLED(CONFIG_OF_DYNAMIC))
2752         WARN_ON(of_reconfig_notifier_register(&spi_of_notifier));
2753
2754     return 0;
2755
2756 err2:
2757     bus_unregister(&spi_bus_type);
2758 err1:
2759     kfree(buf);
2760     buf = NULL;
2761 err0:
2762     return status;
2763 }

2726 static struct notifier_block spi_of_notifier = {
2727     .notifier_call = of_spi_notify,
2728 };

2686 static int of_spi_notify(struct notifier_block *nb, unsigned long action,
2687              void *arg)
2688 {
2689     struct of_reconfig_data *rd = arg;
2690     struct spi_master *master;
2691     struct spi_device *spi;
2692
2693     switch (of_reconfig_get_state_change(action, arg)) {
2694     case OF_RECONFIG_CHANGE_ADD:
2695         master = of_find_spi_master_by_node(rd->dn->parent);
2696         if (master == NULL)
2697             return NOTIFY_OK;   /* not for us */
2698
2699         spi = of_register_spi_device(master, rd->dn);   // ---> 注册设备
2700         put_device(&master->dev);
                // ... ... 
2722
2723     return NOTIFY_OK;
2724 }

1428 #if defined(CONFIG_OF)
1429 static struct spi_device *
1430 of_register_spi_device(struct spi_master *master, struct device_node *nc)
1431 {
1432     struct spi_device *spi;
1433     int rc;
1434     u32 value;
1435
1436     /* Alloc an spi_device */
1437     spi = spi_alloc_device(master);
1438     if (!spi) {
1439         dev_err(&master->dev, "spi_device alloc error for %s\n",
1440             nc->full_name);
1441         rc = -ENOMEM;
1442         goto err_out;
1443     }
1444
1445     /* Select device driver */
1446     rc = of_modalias_node(nc, spi->modalias,
1447                 sizeof(spi->modalias));
1448     if (rc < 0) {
1449         dev_err(&master->dev, "cannot find modalias for %s\n",
1450             nc->full_name);
1451         goto err_out;
1452     }
1453
1454     /* Device address */
1455     rc = of_property_read_u32(nc, "reg", &value);
1456     if (rc) {
1457         dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
1458             nc->full_name, rc);
1459         goto err_out;
1460     }
1461     spi->chip_select = value;
1462
1463     /* Mode (clock phase/polarity/etc.) */
1464     if (of_find_property(nc, "spi-cpha", NULL))
1465         spi->mode |= SPI_CPHA;
1466     if (of_find_property(nc, "spi-cpol", NULL))
1467         spi->mode |= SPI_CPOL;
1468     if (of_find_property(nc, "spi-cs-high", NULL))
1469         spi->mode |= SPI_CS_HIGH;
1470     if (of_find_property(nc, "spi-3wire", NULL))
1471         spi->mode |= SPI_3WIRE;
1472     if (of_find_property(nc, "spi-lsb-first", NULL))
1473         spi->mode |= SPI_LSB_FIRST;
1474
1475     /* 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:
1481             spi->mode |= SPI_TX_DUAL;
1482             break;
1483         case 4:
1484             spi->mode |= SPI_TX_QUAD;
1485             break;
1486         default:
1487             dev_warn(&master->dev,
1488                 "spi-tx-bus-width %d not supported\n",
1489                 value);
1490             break;
1491         }
1492     }
1493
1494     if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
1495         switch (value) {
1496         case 1:
1497             break;
1498         case 2:
1499             spi->mode |= SPI_RX_DUAL;
1500             break;
1501         case 4:
1502             spi->mode |= SPI_RX_QUAD;
1503             break;
1504         default:
1505             dev_warn(&master->dev,
1506                 "spi-rx-bus-width %d not supported\n",
1507                 value);
1508             break;
1509         }
1510     }
1511
1512     /* Device speed */
1513     rc = of_property_read_u32(nc, "spi-max-frequency", &value);
1514     if (rc) {
1515         dev_err(&master->dev, "%s has no valid 'spi-max-frequency' property      (%d)\n",
1516             nc->full_name, rc);
1517         goto err_out;
1518     }
1519     spi->max_speed_hz = value;
1520
1521     /* Store a pointer to the node in the device structure */
1522     of_node_get(nc);
1523     spi->dev.of_node = nc;
1524
1525     /* Register the new device */
1526     rc = spi_add_device(spi);
1527     if (rc) {
1528         dev_err(&master->dev, "spi_device register error %s\n",
1529             nc->full_name);
1530         goto err_out;
1531     }
1532
1533     return spi;
1534
1535 err_out:
1536     spi_dev_put(spi);
1537     return ERR_PTR(rc);
1538 }