<Android> Android与Kernel之间使用proc/sysfs结点通信

Android与Kernel使用结点进行通信.

Android与Kernel通信

Linux中一切皆文件, Android上层与Kernel通信可以使用结点.

public boolean writeProcCmd(int cmd, int data) {
        String new_proc_path = "/proc/mydebug";
        File procFile = new File(new_proc_path);
        try {
            FileOutputStream fw = new FileOutputStream(procFile);
            byte buf[] = new byte[2];
            buf[0] = (byte)cmd;
            buf[1] = (byte)data;
            fw.write(buf);
            fw.flush();
            fw.close();
            return true;
        } catch (IOException e) {
            Log.e(MYTAG, "open output or input stream error");
            return false;
        }
    }

     public int readProcCmd(byte[] buf) {
        String new_proc_path = "/proc/mydebug";
        File procFile = new File(new_proc_path);

        try {
            FileInputStream fr = new FileInputStream(procFile);
            int ret = fr.read(buf);
            fr.close();
            if (ret < 0) {
                Log.e(MYTAG, "proc read input stream error");
                return -1 ;
            }
            return ret;
        } catch (IOException e) {
            Log.e(MYTAG, "open output or input stream error");
            return -1;
        }
    }

Kernel模块与模块通信

同理kernel间模块之间通讯也可以采用结点通讯的方法进行通讯.

#define IDC_BOARD_PROC          "/proc/mydebug"
#define PROC_MYCMD_1                    30
#define PROC_MYCMD_2                    31

static int fts_send_sd_cmd(int present) 
{
    struct file *idcfile;
    mm_segment_t old_fs;
    char opbuf[2] = {0};
    int ret;

    idcfile = filp_open(IDC_BOARD_PROC, O_RDWR, 0);

    if (IS_ERR(idcfile)) {
        pr_err("Open %s failed!\n", IDC_BOARD_PROC);
        return -EINVAL;
    }
    old_fs = get_fs();
    set_fs(KERNEL_DS);

    if (present) {
        opbuf[0] = PROC_MYCMD_1;
    } else {
        opbuf[0] = PROC_MYCMD_2;
    }

    ret = idcfile->f_op->write(idcfile, opbuf, 1, &idcfile->f_pos);

    filp_close(idcfile, NULL);
    set_fs(old_fs);
    if (ret < 0) {
        pr_err("send cmd failed, ret: %d\n", ret);
        return -EINVAL;
    }
    pr_err("send cmd success\n");

    return 0;
}

Kernel端创建结点

　1. 创建proc结点(注意有linux版本区别)

struct kernel_ts_data {
    struct i2c_client *client;
    struct proc_dir_entry *proc;
};
#define PROC_NAME   "mydebug"
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 10, 0))
/************************************************************************
*   Name: kernel_debug_write
*  Brief:interface of write proc
* Input: file point, data buf, data len, no use
* Output: no
* Return: data len
***********************************************************************/
static ssize_t kernel_debug_write(struct file *filp, const char __user *buff, size_t count, loff_t *ppos)
{
    u8 writebuf[PROC_WRITE_BUF_SIZE] = { 0 };
    int buflen = count;
    int writelen = 0;
    int ret = 0;
    char tmp[25];
    struct kernel_ts_data *ts_data = kernel_data;
    struct i2c_client *client = ts_data->client;

    if ((count == 0) || (count > PROC_WRITE_BUF_SIZE)) {
        pr_err("proc wirte count(%d) fail", (int)count);
        return -EINVAL;
    }

    if (copy_from_user(&writebuf, buff, count)) {
        pr_err("copy from user error!!");
        return -EFAULT;
    }

    ts_data->proc_opmode = writebuf[0];

    switch (ts_data->proc_opmode) {
    case PROC_READ_DATA:
    case PROC_WRITE_DATA:
        writelen = buflen - 1;
        if (writelen > 0) {
            ret = kernel_i2c_write(client, writebuf + 1, writelen);
            if (ret < 0) {
                pr_err("write iic error!!");
            }
        }
        break;
    default:
        break;
    }

    if (ret < 0) {
        return ret;
    } else {
        return count;
    }
}

/************************************************************************
*   Name: kernel_debug_read
*  Brief:interface of read proc
* Input: point to the data, no use, no use, read len, no use, no use
* Output: page point to data
* Return: read char number
***********************************************************************/
static ssize_t kernel_debug_read(struct file *filp, char __user *buff, size_t count, loff_t *ppos)
{
    int ret = 0;
    int num_read_chars = 0;
    int readlen = 0;
    u8 buf[PROC_READ_BUF_SIZE] = { 0 };
    struct kernel_ts_data *ts_data = kernel_data;
    struct i2c_client *client = ts_data->client;

    if ((count == 0) || (count > PROC_READ_BUF_SIZE)) {
        pr_err("proc read count(%d) fail", (int)count);
        return -EINVAL;
    }

    switch (ts_data->proc_opmode) {
    case PROC_READ_DATA:
        readlen = count;
        ret = kernel_i2c_read(client, NULL, 0, buf, readlen);
        if (ret < 0) {
            pr_err("read iic error!!");
            return ret;
        }

        num_read_chars = readlen;
        break;
    case PROC_WRITE_DATA:
        break;
    default:
        break;
    }

    if (copy_to_user(buff, buf, num_read_chars)) {
        pr_err("copy to user error!!");
        return -EFAULT;
    }

    return num_read_chars;
}

static const struct file_operations kernel_proc_fops = {
    .owner  = THIS_MODULE,
    .read   = kernel_debug_read,
    .write  = kernel_debug_write,
};
#else
/* interface of write proc */
/************************************************************************
*   Name: kernel_debug_write
*  Brief:interface of write proc
* Input: file point, data buf, data len, no use
* Output: no
* Return: data len
***********************************************************************/
static int kernel_debug_write(struct file *filp,
                           const char __user *buff, unsigned long len, void *data)
{
    int ret = 0;
    u8 writebuf[PROC_WRITE_BUF_SIZE] = { 0 };
    int buflen = len;
    int writelen = 0;
    struct kernel_ts_data *ts_data = kernel_data;
    struct i2c_client *client = ts_data->client;

    if ((count == 0) || (count > PROC_WRITE_BUF_SIZE)) {
        pr_err("proc wirte count(%d) fail", (int)count);
        return -EINVAL;
    }

    if (copy_from_user(&writebuf, buff, buflen)) {
        pr_err("copy from user error!!");
        return -EFAULT;
    }

    ts_data->proc_opmode = writebuf[0];

    switch (ts_data->proc_opmode) {

    case PROC_READ_DATA:
    case PROC_WRITE_DATA:
        writelen = len - 1;
        if (writelen > 0) {
            ret = kernel_i2c_write(client, writebuf + 1, writelen);
            if (ret < 0) {
                pr_err(" write iic error!!");
            }
        }
        break;
    default:
        break;
    }

    if (ret < 0) {
        return ret;
    } else {
        return len;
    }
}

/* interface of read proc */
/************************************************************************
*   Name: kernel_debug_read
*  Brief:interface of read proc
* Input: point to the data, no use, no use, read len, no use, no use
* Output: page point to data
* Return: read char number
***********************************************************************/
static int kernel_debug_read( char *page, char **start,
                           off_t off, int count, int *eof, void *data )
{
    int ret = 0;
    u8 buf[PROC_READ_BUF_SIZE] = { 0 };
    int num_read_chars = 0;
    int readlen = 0;
    struct kernel_ts_data *ts_data = kernel_data;
    struct i2c_client *client = ts_data->client;

    if ((count == 0) || (count > PROC_READ_BUF_SIZE)) {
        pr_err("proc read count(%d) fail", (int)count);
        return -EINVAL;
    }

    switch (ts_data->proc_opmode) {
    case PROC_READ_DATA:
        readlen = count;
        ret = kernel_i2c_read(client, NULL, 0, buf, readlen);
        if (ret < 0) {
            pr_err("read iic error!!");
            return ret;
        }
        num_read_chars = readlen;
        break;
    case PROC_WRITE_DATA:
        break;
    default:
        break;
    }
    memcpy(page, buf, num_read_chars);
    return num_read_chars;
}
#endif

/************************************************************************
* Name: kernel_create_apk_debug_channel
* Brief:  create apk debug channel
* Input: i2c info
* Output:
* Return: return 0 if success
***********************************************************************/
int kernel_create_apk_debug_channel(struct kernel_ts_data *ts_data)
{
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 10, 0))
    ts_data->proc = proc_create(PROC_NAME, 0777, NULL, &kernel_proc_fops);
#else
    ts_data->proc = create_proc_entry(PROC_NAME, 0777, NULL);
#endif
    if (NULL == ts_data->proc) {
        pr_err("create proc entry fail");
        return -ENOMEM;
    } else {
        pr_info("Create proc entry success!");

#if (LINUX_VERSION_CODE < KERNEL_VERSION(3, 10, 0))
        ts_data->proc->write_proc = kernel_debug_write;
        ts_data->proc->read_proc = kernel_debug_read;
#endif
    }

    return 0;
}

/************************************************************************
* Name: kernel_release_apk_debug_channel
* Brief:  release apk debug channel
* Input:
* Output:
* Return:
***********************************************************************/
void kernel_release_apk_debug_channel(struct kernel_ts_data *ts_data)
{

    if (ts_data->proc) {
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3, 10, 0))
        proc_remove(ts_data->proc);
#else
        remove_proc_entry(PROC_NAME, NULL);
#endif
    }
}

2. 创建sysfs结点, 以I2C设备为例

enum {
    RWREG_OP_READ = 0,
    RWREG_OP_WRITE = 1,
};
static struct rwreg_operation_t {
    int type;         /*  0: read, 1: write */
    int reg;        /*  register */
    int len;        /*  read/write length */
    int val;      /*  length = 1; read: return value, write: op return */
    int res;     /*  0: success, otherwise: fail */
    char *opbuf;        /*  length >= 1, read return value, write: op return */
} rw_op;
/************************************************************************
* Name: kernel_rwreg_show
* Brief:  no
* Input: device, device attribute, char buf
* Output: no
* Return: EPERM
***********************************************************************/
static ssize_t kernel_rwreg_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    int count;
    int i;
    struct input_dev *input_dev = kernel_data->input_dev;

    mutex_lock(&input_dev->mutex);

    if (rw_op.len < 0) {
        count = snprintf(buf, PAGE_SIZE, "Invalid cmd line\n");
    } else if (rw_op.len == 1) {
        if (RWREG_OP_READ == rw_op.type) {
            if (rw_op.res == 0) {
                count = snprintf(buf, PAGE_SIZE, "Read %02X: %02X\n", rw_op.reg, rw_op.val);
            } else {
                count = snprintf(buf, PAGE_SIZE, "Read %02X failed, ret: %d\n", rw_op.reg,  rw_op.res);
            }
        } else {
            if (rw_op.res == 0) {
                count = snprintf(buf, PAGE_SIZE, "Write %02X, %02X success\n", rw_op.reg,  rw_op.val);
            } else {
                count = snprintf(buf, PAGE_SIZE, "Write %02X failed, ret: %d\n", rw_op.reg,  rw_op.res);
            }
        }
    } else {
        if (RWREG_OP_READ == rw_op.type) {
            count = snprintf(buf, PAGE_SIZE, "Read Reg: [%02X]-[%02X]\n", rw_op.reg, rw_op.reg + rw_op.len);
            count += snprintf(buf + count, PAGE_SIZE, "Result: ");
            if (rw_op.res) {
                count += snprintf(buf + count, PAGE_SIZE, "failed, ret: %d\n", rw_op.res);
            } else {
                if (rw_op.opbuf) {
                    for (i = 0; i < rw_op.len; i++) {
                        count += snprintf(buf + count, PAGE_SIZE, "%02X ", rw_op.opbuf[i]);
                    }
                    count += snprintf(buf + count, PAGE_SIZE, "\n");
                }
            }
        } else {
            ;
            count = snprintf(buf, PAGE_SIZE, "Write Reg: [%02X]-[%02X]\n", rw_op.reg, rw_op.reg + rw_op.len - 1);
            count += snprintf(buf + count, PAGE_SIZE, "Write Data: ");
            if (rw_op.opbuf) {
                for (i = 1; i < rw_op.len; i++) {
                    count += snprintf(buf + count, PAGE_SIZE, "%02X ", rw_op.opbuf[i]);
                }
                count += snprintf(buf + count, PAGE_SIZE, "\n");
            }
            if (rw_op.res) {
                count += snprintf(buf + count, PAGE_SIZE, "Result: failed, ret: %d\n", rw_op.res);
            } else {
                count += snprintf(buf + count, PAGE_SIZE, "Result: success\n");
            }
        }
        /*if (rw_op.opbuf) {
            kernel_kfree(rw_op.opbuf);
            rw_op.opbuf = NULL;
        }*/
    }
    mutex_unlock(&input_dev->mutex);

    return count;
}

static int shex_to_int(const char *hex_buf, int size)
{
    int i;
    int base = 1;
    int value = 0;
    char single;

    for (i = size - 1; i >= 0; i--) {
        single = hex_buf[i];

        if ((single >= '0') && (single <= '9')) {
            value += (single - '0') * base;
        } else if ((single >= 'a') && (single <= 'z')) {
            value += (single - 'a' + 10) * base;
        } else if ((single >= 'A') && (single <= 'Z')) {
            value += (single - 'A' + 10) * base;
        } else {
            return -EINVAL;
        }

        base *= 16;
    }

    return value;
}


static u8 shex_to_u8(const char *hex_buf, int size)
{
    return (u8)shex_to_int(hex_buf, size);
}
/*
 * Format buf:
 * [0]: '0' write, '1' read(reserved)
 * [1-2]: addr, hex
 * [3-4]: length, hex
 * [5-6]...[n-(n+1)]: data, hex
 */
static int kernel_parse_buf(const char *buf, size_t cmd_len)
{
    int length;
    int i;
    char *tmpbuf;

    rw_op.reg = shex_to_u8(buf + 1, 2);
    length = shex_to_int(buf + 3, 2);

    if (buf[0] == '1') {
        rw_op.len = length;
        rw_op.type = RWREG_OP_READ;
        kernel_DEBUG("read %02X, %d bytes", rw_op.reg, rw_op.len);
    } else {
        if (cmd_len < (length * 2 + 5)) {
            pr_err("data invalided!\n");
            return -EINVAL;
        }
        kernel_DEBUG("write %02X, %d bytes", rw_op.reg, length);

        /* first byte is the register addr */
        rw_op.type = RWREG_OP_WRITE;
        rw_op.len = length + 1;
    }

    if (rw_op.len > 0) {
        tmpbuf = (char *)kzalloc(rw_op.len, GFP_KERNEL);
        if (!tmpbuf) {
            pr_err("allocate memory failed!\n");
            return -ENOMEM;
        }

        if (RWREG_OP_WRITE == rw_op.type) {
            tmpbuf[0] = rw_op.reg & 0xFF;
            kernel_DEBUG("write buffer: ");
            for (i = 1; i < rw_op.len; i++) {
                tmpbuf[i] = shex_to_u8(buf + 5 + i * 2 - 2, 2);
                kernel_DEBUG("buf[%d]: %02X", i, tmpbuf[i] & 0xFF);
            }
        }
        rw_op.opbuf = tmpbuf;
    }

    return rw_op.len;
}



/************************************************************************
* Name: kernel_rwreg_store
* Brief:  read/write register
* Input: device, device attribute, char buf, char count
* Output: print register value
* Return: char count
***********************************************************************/
static ssize_t kernel_rwreg_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct input_dev *input_dev = kernel_data->input_dev;
    struct i2c_client *client = container_of(dev, struct i2c_client, dev);
    ssize_t cmd_length = 0;

    mutex_lock(&input_dev->mutex);
    cmd_length = count - 1;

    if (rw_op.opbuf) {
        kernel_kfree(rw_op.opbuf);
        rw_op.opbuf = NULL;
    }

    kernel_DEBUG("cmd len: %d, buf: %s", (int)cmd_length, buf);
    /* compatible old ops */
    if (2 == cmd_length) {
        rw_op.type = RWREG_OP_READ;
        rw_op.len = 1;

        rw_op.reg = shex_to_int(buf, 2);
    } else if (4 == cmd_length) {
        rw_op.type = RWREG_OP_WRITE;
        rw_op.len = 1;
        rw_op.reg = shex_to_int(buf, 2);
        rw_op.val = shex_to_int(buf + 2, 2);

    } else if (cmd_length < 5) {
        pr_err("Invalid cmd buffer");
        mutex_unlock(&input_dev->mutex);
        return -EINVAL;
    } else {
        rw_op.len = kernel_parse_buf(buf, cmd_length);
    }

    if (rw_op.len < 0) {
        pr_err("cmd buffer error!");

    } else {
        if (RWREG_OP_READ == rw_op.type) {
            if (rw_op.len == 1) {
                u8 reg, val;
                reg = rw_op.reg & 0xFF;
                rw_op.res = kernel_i2c_read_reg(client, reg, &val);
                rw_op.val = val;
            } else {
                char reg;
                reg = rw_op.reg & 0xFF;

                rw_op.res = kernel_i2c_read(client, &reg, 1, rw_op.opbuf, rw_op.len);
            }

            if (rw_op.res < 0) {
                pr_err("Could not read 0x%02x", rw_op.reg);
            } else {
                pr_info("read 0x%02x, %d bytes successful", rw_op.reg, rw_op.len);
                rw_op.res = 0;
            }

        } else {
            if (rw_op.len == 1) {
                u8 reg, val;
                reg = rw_op.reg & 0xFF;
                val = rw_op.val & 0xFF;
                rw_op.res = kernel_i2c_write_reg(client, reg, val);
            } else {
                rw_op.res = kernel_i2c_write(client, rw_op.opbuf, rw_op.len);
            }
            if (rw_op.res < 0) {
                pr_err("Could not write 0x%02x", rw_op.reg);

            } else {
                pr_info("Write 0x%02x, %d bytes successful", rw_op.val, rw_op.len);
                rw_op.res = 0;
            }
        }
    }

    mutex_unlock(&input_dev->mutex);

    return count;
}
/* add your attr in here*/
static struct attribute *fts_attributes[] = {
    &dev_attr_rw_reg.attr,
    NULL
};

static struct attribute_group fts_attribute_group = {
    .attrs = fts_attributes
};
/************************************************************************
* Name: kernel_create_sysfs
* Brief: create sysfs interface
* Input:
* Output:
* Return: return 0 if success
***********************************************************************/
int kernel_create_sysfs(struct i2c_client *client)
{
    int ret = 0;

    ret = sysfs_create_group(&client->dev.kobj, &kernel_attribute_group);
    if (ret) {
        pr_err("[EX]: sysfs_create_group() failed!!");
        sysfs_remove_group(&client->dev.kobj, &kernel_attribute_group);
        return -ENOMEM;
    } else {
        pr_info("[EX]: sysfs_create_group() succeeded!!");
    }

    return ret;
}
/************************************************************************
* Name: kernel_remove_sysfs
* Brief: remove sysfs interface
* Input:
* Output:
* Return:
***********************************************************************/
int kernel_remove_sysfs(struct i2c_client *client)
{
    sysfs_remove_group(&client->dev.kobj, &kernel_attribute_group);
    return 0;
}