Re: aio_read() in character driver is not getting calls when making aio_read system call

[Parav Pandit <paravpandit@xxxxxxxxx>]

file_operations structure contains aio_read and aio_write function pointers.

You may be refering to some old sources.

check at latest 2.6.18 sources.

 

Additionally, when I comment the .read = dbg_read function, it comes to my dbg_aio_read().

Which is working also.

 

Somewhere I read about O_DIRECT flag to pass when open a device.

Actually, for character device files, it default diverts requests to the syncronous read if O_DIRECT flag is not passed.

 

it is defined in fcntl.h file with __USE_GNU flag.

But I am keep on getting compilation error when I pass O_DIRECT flag.

 

Any idea, how can I remove this O_DIRECT undefined error?

 

Regards,

Parav Pandit

 

Rajath N R <rajathnr@xxxxxxxxx> wrote:

Hi Parav Pandit,

     I don`t think file_operations structure contain aio_read variable. If any thing wrong please let me know.
 

struct file_operations {
         loff_t (*llseek) (struct file *, loff_t, int);
         ssize_t (*read) (struct file *, char *, size_t, loff_t *);
           ssize_t (*write) (struct file *, const char *, size_t, loff_t *);
         int (*readdir) (struct file *, void *, filldir_t);
         unsigned int (*poll) (struct file *, struct poll_table_struct *);
         int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);  
         int (*mmap) (struct file *, struct vm_area_struct *);
         int (*open) (struct inode *, struct file *);
         int (*flush) (struct file *);
  
       int (*release) (struct inode *, struct file *);  
         int (*fsync) (struct file *, struct dentry *);
         int (*fasync) (int, struct file *, int);
         int (*check_media_change) (kdev_t dev);
         int (*revalidate) (kdev_t dev);
         int (*lock) (struct file *, int, struct file_lock *);  
};

Regards,
Rajath.N.R

On 12/8/06, Parav Pandit <paravpandit@xxxxxxxxx> wrote:

Hi,

 

I am adding aio_read and aio_write hooks to my character driver.

 

When I make aio_read() system call, for some reason instead of dbg_aio_read(), kernel is calling the syncronous dbg_read() function.

 

Here is the application level code for opening the file:

 

fd = open("/dev/debug_driver", O_RDONLY );

 

Below is the file_operations structure:

static struct file_operations debug_fops = {

.owner = THIS_MODULE,

.aio_read = dbg_aio_read,

.read = dbg_read,

.ioctl = dbg_ioctl,

.open = dbg_open,

.release = dbg_release,

};

 

What additional thing I need to do so that my char driver aio_read is called when application calls aio_read() system call?

Interestingly same code is working if i open a normal text file.

 

Regards,

Parav Pandit

 

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