举一个例程，关于linux spi 读写刷除 winbon flash 的例程，要有设备树和详细说明

以下是一个示例代码，演示了如何在Linux系统中使用SPI接口读写和擦除Winbond SPI Flash。这个示例代码使用设备树来描述SPI设备和SPI Flash，以便在Linux内核启动时自动加载SPI驱动程序。

设备树描述：

&spi0 {
    #address-cells = <1>;
    #size-cells = <0>;
    pinctrl-names = "default";
    pinctrl-0 = <&spi0_pins>;
    status = "okay";

    flash: w25q64@0 {
        compatible = "winbond,w25q64";
        spi-max-frequency = <10000000>;
        reg = <0>;
    };
};

&iomuxc {
    spi0_pins: spi0 {
        pinctrl-single,pins = <
            MX6QDL_PAD_EIM_D16__GPIO3_IO16   0x82
            MX6QDL_PAD_EIM_D17__ECSPI1_SS0  0x82
            MX6QDL_PAD_EIM_D18__ECSPI1_SCLK 0x82
            MX6QDL_PAD_EIM_D19__ECSPI1_MISO 0x82
            MX6QDL_PAD_EIM_D20__ECSPI1_MOSI 0x82
        >;
    };
};

其中，`&spi0`描述了SPI控制器和SPI Flash，`flash`节点的`compatible`属性指定了该节点对应的Flash型号。`spi-max-frequency`属性指定了SPI Flash的最大时钟频率，`reg`属性指定了Flash在SPI总线上的地址。`&iomuxc`节点描述了SPI控制器的引脚连接。

示例代码：

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/spi/spi.h>

#define WINBOND_W25Q64_ID 0xEF4017

static struct spi_device *flash_device;

static int flash_read_id(struct spi_device *spi)
{
    u8 tx_buf[4] = {0x9F, 0x00, 0x00, 0x00};
    u8 rx_buf[4] = {0};

    struct spi_message msg;
    struct spi_transfer xfers[2];

    xfers[0].tx_buf = tx_buf;
    xfers[0].len = 4;
    xfers[1].rx_buf = rx_buf;
    xfers[1].len = 4;

    spi_message_init(&msg);
    spi_message_add_tail(&xfers[0], &msg);
    spi_message_add_tail(&xfers[1], &msg);

    spi_sync(spi, &msg);

    return (rx_buf[1] << 16) | (rx_buf[2] << 8) | rx_buf[3];
}

static int flash_erase(struct spi_device *spi, unsigned int offset, unsigned int len)
{
    u8 tx_buf[4] = {0x20, (offset >> 16) & 0xFF, (offset >> 8) & 0xFF, offset & 0xFF};

    struct spi_message msg;
    struct spi_transfer xfer;

    xfer.tx_buf = tx_buf;
    xfer.len = 4;

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    spi_sync(spi, &msg);

    msleep(10);

    tx_buf[0] = 0xD8;

    xfer.tx_buf = tx_buf;
    xfer.len = 1;

    spi_message_init(&msg);
    spi_message_add_tail(&xfer, &msg);

    spi_sync(spi, &msg);

    return 0;
}

static int flash_write(struct spi_device *spi, unsigned int offset, unsigned int len, const u8 *buf)
{
    u8 tx_buf[4] = {0x02, (offset >> 16) & 0xFF, (offset >> 8) & 0xFF, offset & 0xFF};

    struct spi_message msg;
    struct spi_transfer xfers[2];

    xfers[0].tx_buf = tx_buf;
    xfers[0].len = 4;
    xfers[1].tx_buf = buf;
    xfers[1].len = len;

    spi_message_init(&msg);
    spi_message_add_tail(&xfers[0], &msg);
    spi_message_add_tail(&xfers[1], &msg);

    spi_sync(spi, &msg);

    return 0;
}

static int flash_probe(struct spi_device *spi)
{
    int ret;

    if (spi->dev.of_node) {
        struct device_node *np = spi->dev.of_node;
        const char *compat = of_device_get_match_data(&spi->dev);

        if (!of_device_is_compatible(np, compat)) {
            dev_err(&spi->dev, "device tree mismatch\n");
            return -EINVAL;
        }
    }

    if (spi->max_speed_hz > 10000000)
        spi->max_speed_hz = 10000000;

    if (spi->bits_per_word != 8)
        spi->bits_per_word = 8;

    ret = spi_setup(spi);
    if (ret < 0)
        return ret;

    ret = flash_read_id(spi);
    if (ret != WINBOND_W25Q64_ID) {
        dev_err(&spi->dev, "unknown flash id: %x\n", ret);
        return -ENODEV;
    }

    flash_device = spi;

    return 0;
}

static int flash_remove(struct spi_device *spi)
{
    if (flash_device == spi)
        flash_device = NULL;

    return 0;
}

static const struct spi_device_id flash_id_table[] = {
    {"w25q64", 0},
    {},
};
MODULE_DEVICE_TABLE(spi, flash_id_table);

static const struct of_device_id flash_of_match[] = {
    { .compatible = "winbond,w25q64", .data = "w25q64" },
    {},
};
MODULE_DEVICE_TABLE(of, flash_of_match);

static struct spi_driver flash_driver = {
    .driver = {
        .name = "winbond-flash",
        .owner = THIS_MODULE,
        .of_match_table = flash_of_match,
    },
    .probe = flash_probe,
    .remove = flash_remove,
    .id_table = flash_id_table,
};

static int __init flash_init(void)
{
    return spi_register_driver(&flash_driver);
}

static void __exit flash_exit(void)
{
    spi_unregister_driver(&flash_driver);
}

module_init(flash_init);
module_exit(flash_exit);

MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("Winbond W25Q64 SPI flash driver");
MODULE_LICENSE("GPL");

在这个示例代码中，`flash_read_id`函数用于读取Flash的ID，`flash_erase`函数用于擦除Flash的指定区域，`flash_write`函数用于向Flash写入数据。`flash_probe`函数用于在SPI设备匹配时初始化Flash设备，`flash_remove`函数用于在SPI设备卸载时清理Flash设备。`flash_driver`结构体定义了SPI驱动程序的属性，以及驱动程序的入口和出口函数。`flash_init`和`flash_exit`函数分别在驱动程序加载和卸载时调用。