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2012-04-16 12:18:24

原文地址:spi网站2 作者:dingzerong


==========================================================
[spi driver]
[Linux下spi驱动开发(1)]
Sailor_forever Forward My Dreams( long lifetime)
http://blog.csdn.net/sailor_8318/article/details/5977733

Linux下SPI从设备驱动的编写

如果你需要使用spi驱动的接口,不是去修改驱动的实现代码,因为它只负责完成spi的硬件交互功能。
你使用spi功能的代码只需要用到spi.h中定义的方法就可以了,这就是linux driver layers framework的可人之处。
我们通过一个简单的例子来实际理解一下:
#include
#include
#include
#define TEST_REG 0x02
static int test_read_reg(struct spi_device *spi, int reg)
{
char buf[2];
buf[0] = reg << 2;
buf[1] = 0;
spi_write_then_read(spi, buf, 2, buf, 2);
return buf[1] << 8 | buf[0];
}
static int spi_test_probe(struct spi_device *spi)
{
printk("TEST_REG: 0x%02x\n", test_read_reg(spi, TEST_REG));
return 0;
}
static int spi_test_remove(struct spi_device *spi)
{
return 0;
}
static struct spi_driver spi_test_driver = {
.probe = spi_test_probe,
.remove = spi_test_remove,
.driver = {
.name = "testHW",
},
};
static int __init spi_test_init(void)
{
return spi_register_driver(&spi_test_driver);
}
static void __exit spi_test_exit(void)
{
spi_unregister_driver(&spi_test_driver);
}
module_init(spi_test_init);
module_exit(spi_test_exit);
MODULE_DESCRIPTION("spi device test");
MODULE_LICENSE("GPL");

在这个驱动中,你只需要用spi_register_driver向系统进行注册,就可以让系统用你指定的与 .name 相匹配的硬件交互代码
去执行你的读写请求。
几乎在所有与spi相关的函数中都会用到struct spi_device *spi这个指针,probe函数正好把这个指针传给你,保存好这个指针,你就可以在驱动的任何地方通过他去处理与spi设备相关的操作。
 
 
 
==============================================
四、m25p10驱动测试
    目标:在华清远见的FS_S5PC100平台上编写一个简单的spi驱动模块,在probe阶段实现对m25p10的ID号探测、flash擦除、flash状态读取、flash写入、flash读取等操作。代码已经经过测试,运行于2.6.35内核。理解下面代码需要参照m25p10的芯片手册。其实下面的代码和处理器没有太大关系,这也是spi子系统的分层特点。

view plaincopy to clipboardprint?#include   
#include   
#include  
#include  
#include  
#include  
#include  
#include    // kzalloc 
#include  
 
#define FLASH_PAGE_SIZE     256 
 
/* Flash Operating Commands */ 
#define CMD_READ_ID         0x9f 
#define CMD_WRITE_ENABLE    0x06     
#define CMD_BULK_ERASE      0xc7 
#define CMD_READ_BYTES      0x03 
#define CMD_PAGE_PROGRAM    0x02 
#define CMD_RDSR            0x05     
 
/* Status Register bits. */ 
#define SR_WIP          1   /* Write in progress */ 
#define SR_WEL          2   /* Write enable latch */ 
 
/* ID Numbers */ 
#define MANUFACTURER_ID     0x20 
#define DEVICE_ID           0x1120 
 
/* Define max times to check status register before we give up. */ 
#define MAX_READY_WAIT_COUNT    100000 
#define CMD_SZ  4 
 
struct m25p10a { 
    struct spi_device   *spi; 
    struct mutex        lock; 
    char    erase_opcode; 
    char    cmd[ CMD_SZ ]; 
}; 
 
/* 
 * Internal Helper functions  
 */ 
 
/* 
 * Read the status register, returning its value in the location 
 * Return the status register value. 
 * Returns negative if error occurred. 
 */ 
static int read_sr(struct m25p10a *flash) 

    ssize_t retval; 
    u8 code = CMD_RDSR; 
    u8 val; 
 
    retval = spi_write_then_read(flash->spi, &code, 1, &val, 1); 
 
    if (retval < 0) { 
        dev_err(&flash->spi->dev, "error %d reading SR\n", 
                (int) retval); 
        return retval; 
    } 
 
    return val; 

 
/* 
 * Service routine to read status register until ready, or timeout occurs. 
 * Returns non-zero if error. 
 */ 
static int wait_till_ready(struct m25p10a *flash) 

    int count; 
    int sr;  
 
    /* one chip guarantees max 5 msec wait here after page writes, 
     * but potentially three seconds (!) after page erase. 
     */ 
    for (count = 0; count < MAX_READY_WAIT_COUNT; count++) { 
        if ((sr = read_sr(flash)) < 0) 
            break; 
        else if (!(sr & SR_WIP)) 
            return 0; 
 
        /* REVISIT sometimes sleeping would be best */ 
    }    
    printk( "in (%s): count = %d\n", count ); 
 
    return 1; 

 
/* 
 * Set write enable latch with Write Enable command. 
 * Returns negative if error occurred. 
 */ 
static inline int write_enable( struct m25p10a *flash ) 

    flash->cmd[0] = CMD_WRITE_ENABLE; 
    return spi_write( flash->spi, flash->cmd, 1 ); 

 
/* 
 * Erase the whole flash memory 
 * 
 * Returns 0 if successful, non-zero otherwise. 
 */ 
static int erase_chip( struct m25p10a *flash ) 

    /* Wait until finished previous write command. */ 
    if (wait_till_ready(flash)) 
        return -1; 
 
    /* Send write enable, then erase commands. */ 
    write_enable( flash ); 
    flash->cmd[0] = CMD_BULK_ERASE; 
    return spi_write( flash->spi, flash->cmd, 1 ); 

 
/* 
 * Read an address range from the flash chip.  The address range 
 * may be any size provided it is within the physical boundaries. 
 */ 
static int m25p10a_read( struct m25p10a *flash, loff_t from,  
        size_t len, char *buf ) 

    int r_count = 0, i; 
 
    flash->cmd[0] = CMD_READ_BYTES; 
    flash->cmd[1] = from >> 16; 
    flash->cmd[2] = from >> 8; 
    flash->cmd[3] = from; 
     
#if 1 
    struct spi_transfer st[2]; 
    struct spi_message  msg; 
     
    spi_message_init( &msg ); 
    memset( st, 0, sizeof(st) ); 
 
    flash->cmd[0] = CMD_READ_BYTES; 
    flash->cmd[1] = from >> 16; 
    flash->cmd[2] = from >> 8; 
    flash->cmd[3] = from; 
 
    st[ 0 ].tx_buf = flash->cmd; 
    st[ 0 ].len = CMD_SZ; 
    spi_message_add_tail( &st[0], &msg ); 
 
    st[ 1 ].rx_buf = buf; 
    st[ 1 ].len = len; 
    spi_message_add_tail( &st[1], &msg ); 
 
    mutex_lock( &flash->lock ); 
     
    /* Wait until finished previous write command. */ 
    if (wait_till_ready(flash)) { 
        mutex_unlock( &flash->lock ); 
        return -1; 
    } 
 
    spi_sync( flash->spi, &msg ); 
    r_count = msg.actual_length - CMD_SZ; 
    printk( "in (%s): read %d bytes\n", __func__, r_count ); 
    for( i = 0; i < r_count; i++ ) { 
        printk( "0x%02x\n", buf[ i ] ); 
    } 
 
    mutex_unlock( &flash->lock ); 
#endif 
 
    return 0; 

 
/* 
 * Write an address range to the flash chip.  Data must be written in 
 * FLASH_PAGE_SIZE chunks.  The address range may be any size provided 
 * it is within the physical boundaries. 
 */ 
static int m25p10a_write( struct m25p10a *flash, loff_t to,  
        size_t len, const char *buf ) 

    int w_count = 0, i, page_offset; 
    struct spi_transfer st[2]; 
    struct spi_message  msg; 
#if 1 
    if (wait_till_ready(flash)) {    //读状态,等待ready 
        mutex_unlock( &flash->lock ); 
        return -1; 
    } 
#endif 
    write_enable( flash );  //写使能 
     
    spi_message_init( &msg ); 
    memset( st, 0, sizeof(st) ); 
 
    flash->cmd[0] = CMD_PAGE_PROGRAM; 
    flash->cmd[1] = to >> 16; 
    flash->cmd[2] = to >> 8; 
    flash->cmd[3] = to; 
 
    st[ 0 ].tx_buf = flash->cmd; 
    st[ 0 ].len = CMD_SZ; 
    spi_message_add_tail( &st[0], &msg ); 
 
    st[ 1 ].tx_buf = buf; 
    st[ 1 ].len = len; 
    spi_message_add_tail( &st[1], &msg ); 
 
    mutex_lock( &flash->lock ); 
 
    /* get offset address inside a page */ 
    page_offset = to % FLASH_PAGE_SIZE;      
 
    /* do all the bytes fit onto one page? */ 
    if( page_offset + len <= FLASH_PAGE_SIZE ) { // yes 
        st[ 1 ].len = len;  
        printk("%d, cmd = %d\n", st[ 1 ].len, *(char *)st[0].tx_buf); 
        //while(1) 
        { 
        spi_sync( flash->spi, &msg ); 
        } 
        w_count = msg.actual_length - CMD_SZ; 
    } 
    else {  // no 
    } 
    printk( "in (%s): write %d bytes to flash in total\n", __func__, w_count ); 
    mutex_unlock( &flash->lock ); 
    return 0; 

 
static int check_id( struct m25p10a *flash )  
{  
    char buf[10] = {0};  
    flash->cmd[0] = CMD_READ_ID; 
    spi_write_then_read( flash->spi, flash->cmd, 1, buf, 3 );  
    printk( "Manufacture ID: 0x%x\n", buf[0] ); 
    printk( "Device ID: 0x%x\n", buf[1] | buf[2]  << 8 ); 
    return buf[2] << 16 | buf[1] << 8 | buf[0];  
}  
 
static int m25p10a_probe(struct spi_device *spi)  
{  
    int ret = 0; 
    struct m25p10a  *flash; 
    char buf[ 256 ]; 
    printk( "%s was called\n", __func__ ); 
    flash = kzalloc( sizeof(struct m25p10a), GFP_KERNEL ); 
    if( !flash ) { 
        return -ENOMEM; 
    } 
    flash->spispi = spi; 
    mutex_init( &flash->lock ); 
    /* save flash as driver's private data */ 
    spi_set_drvdata( spi, flash ); 
     
    check_id( flash );    //读取ID 
#if 1 
    ret = erase_chip( flash );  //擦除 
    if( ret < 0 ) { 
        printk( "erase the entirely chip failed\n" ); 
    } 
    printk( "erase the whole chip done\n" ); 
    memset( buf, 0x7, 256 ); 
    m25p10a_write( flash, 0, 20, buf); //0地址写入20个7 
    memset( buf, 0, 256 ); 
    m25p10a_read( flash, 0, 25, buf ); //0地址读出25个数 
#endif 
    return 0;  
}  
 
static int m25p10a_remove(struct spi_device *spi)  
{  
    return 0;  
}  
 
static struct spi_driver m25p10a_driver = {  
    .probe = m25p10a_probe,  
    .remove = m25p10a_remove,  
    .driver = {  
        .name = "m25p10a",  
    },  
};  
 
static int __init m25p10a_init(void)  
{  
    return spi_register_driver(&m25p10a_driver);  
}  
 
static void __exit m25p10a_exit(void)  
{  
    spi_unregister_driver(&m25p10a_driver);  
}  
 
module_init(m25p10a_init);  
module_exit(m25p10a_exit);  
 
MODULE_DESCRIPTION("m25p10a driver for FS_S5PC100");  
MODULE_LICENSE("GPL");
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