Write USB Device Driver entry not called

Write USB Device Driver entry not called

[eshwar]

I am writing usb Device Driver for vendor specific Device for the kernel
2.6.8 ... When i have loaded my skelton usb driver
ioctl,read,probe,disconnect,release entry points are working fine but when i
issue write() returns as bad file descriptor.... even though i have open the
device file with S_IWUSR

The error message is comming vfs_wirte() function

 if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;

It seems to be f_mode is not set with FMODE_WRITE

Can any one help me to fix this problem.... Thanks in Advance

Regards
Eshwar


The skelton driver is as follows and application code follows the driver
code...

Driver.c

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/usb.h>
#include <asm/uaccess.h>


/* Function prototypes */
static int otg_cli_open ( struct inode *inode, struct file *file);
/* Function prototypes */
static int otg_cli_open ( struct inode *inode, struct file *file);
static void otg_cli_disconnect( struct usb_interface *intf);
static int otg_cli_release ( struct inode *inode, struct file *file);
static ssize_t otg_cli_read (struct file *file, char *buffer, size_t count,
                          loff_t *ppos);
static ssize_t otg_cli_write (struct file *file, const char *buffer,
                          size_t count, loff_t *ppos);
static int otg_cli_probe( struct usb_interface *intf,
                          const struct usb_device_id *id);

static struct usb_device_id otg_device_id[] = {
        { USB_INTERFACE_INFO(USB_CLASS_VENDOR_SPEC, 0x00, 0xff) },
        {},
 };

struct usb_driver otg_cli_driver = {
        .owner      =   THIS_MODULE,
        .name       =   "xyz",
        .probe      =   otg_cli_probe,
        .disconnect =   otg_cli_disconnect,
        .id_table   =   otg_device_id,
};

static struct file_operations otg_cli_fops = {
        .owner   =      THIS_MODULE,
        .write    =     otg_cli_write,
        .open    =      otg_cli_open,
        .read    =      otg_cli_read,
        .release =      otg_cli_release,
};

static struct usb_class_driver otg_cli_class = {
        .name =         "xyz",
        .fops =         &otg_cli_fops,
};

static struct usb_class_driver otg_cli_class = {
        .name =         "moschip-otg",
        .fops =         &otg_cli_fops,
        .mode =         S_IRWXU | S_IRWXG | S_IRWXO | S_IFCHR,
        .minor_base =   250,
};

static int otg_cli_ioctl ( struct inode *inode, struct file *file,
                       unsigned int cmd, unsigned long arg)
{

    printk("Eshwar: otg_cli_ioctl");
   return 0;
}

static ssize_t otg_cli_read (struct file *file, char *buffer,
          size_t count, loff_t *ppos)
{
     printk("Eshwar: otg_cli_read");
     return 0;
}

static ssize_t otg_cli_write (struct file *file, const char *buffer,
        size_t count,loff_t *ppos)
{
    printk("Eshwar: otg_cli_write");
    return 0;
}

static int otg_cli_open ( struct inode *inode, struct file *file)
{
    printk("Eshwar: otg_cli_open");
   return 0;
}

static int otg_cli_release ( struct inode *inode, struct file *file)
{
    printk("Eshwar: otg_cli_release");
    return 0;
}

static int otg_cli_probe( struct usb_interface *intf,
                         const struct usb_device_id *id)
{

    printk("Eshwar: otg_cli_probe\n");
    return 0;
}

static void otg_cli_disconnect( struct usb_interface *intf)
{
        printk("Eshwar: otg_cli_disconnect\n");
    usb_deregister_dev (intf, &otg_cli_class);
}

static int __init otg_cli_init(void)
{
    printk ("Eshwar: otg_cli_init\n");
    /* register this driver with the USB subsystem */
    usb_register(&otg_cli_driver);
    return 0;
}

/* OTG cleanup module */
static void __exit otg_cli_exit(void)
{
    usb_deregister(&otg_cli_driver);
}

module_init (otg_cli_init);
module_exit (otg_cli_exit);

app.c


int main(int argc, char *argv[])
{
    int devfd;
    char send[512];

    memset(send,'a',512);

  devfd = open("/dev/usb/dabusb10",O_APPEND | S_IRUSR| S_IWUSR );
  if ( write(devfd,send,512) < 0) {
       printf ("write Failed\n");
       return  -1;
  }

  return 0;

}

Re: Write USB Device Driver entry not called

[Raj]

> 
>   devfd = open("/dev/usb/dabusb10",O_APPEND | S_IRUSR| S_IWUSR );

Did your open() succeed here ??? i guess S_IRUSR etc is used when you
create a new file and not when you open a new one.

>   if ( write(devfd,send,512) < 0) {
>        printf ("write Failed\n");
>        return  -1;
>   }

well , if open fails above, then....

-- Raj

Re: Write USB Device Driver entry not called

[eshwar]

Open is sucessfull.... I don't think the problem the flags of open

Eshwar


----- Original Message ----- 
From: "Raj" <inguva@gmail.com>
To: "eshwar" <eshwar@moschip.com>
Cc: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Sent: Wednesday, October 13, 2004 11:45 AM
Subject: Re: Write USB Device Driver entry not called


> > 
> >   devfd = open("/dev/usb/dabusb10",O_APPEND | S_IRUSR| S_IWUSR );
> 
> Did your open() succeed here ??? i guess S_IRUSR etc is used when you
> create a new file and not when you open a new one.
> 
> >   if ( write(devfd,send,512) < 0) {
> >        printf ("write Failed\n");
> >        return  -1;
> >   }
> 
> well , if open fails above, then....
> 
> -- Raj

Re: Write USB Device Driver entry not called

[Raj]

On Thu, 21 Oct 2004 23:22:02 +0530, eshwar <eshwar@moschip.com> wrote:
> Open is sucessfull.... I don't think the problem the flags of open
> 
Try this: open("/dev/usb/dabusb10",O_WRONLY | O_APPEND );

######
raj
######

Re: Write USB Device Driver entry not called

[Alan Cox]

On Iau, 2004-10-21 at 18:52, eshwar wrote:
> Open is sucessfull.... I don't think the problem the flags of open

I do. See any book on C/Unix style file opening. For an existing file
you want
		open("foo", O_flags)

for a new file possibly

		open("foo", O_CREAT|o_flags, S_Iblah)

Re: Write USB Device Driver entry not called

[eshwar]

I agree but the return value from the vfs_write should not be the -EBADF
(Bad File descriptor) it might be -EACCES (premission denied)... Correct me
if I am wrong...

this can be code in fs/read_write.c vfs_write()

 if (!(file->f_mode & FMODE_WRITE))
  return -EACCES;

Eshwar

----- Original Message -----
From: "Alan Cox" <alan@lxorguk.ukuu.org.uk>
To: "eshwar" <eshwar@moschip.com>
Cc: "Raj" <inguva@gmail.com>; "Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>
Sent: Wednesday, October 13, 2004 4:07 PM
Subject: Re: Write USB Device Driver entry not called


> On Iau, 2004-10-21 at 18:52, eshwar wrote:
> > Open is sucessfull.... I don't think the problem the flags of open
>
> I do. See any book on C/Unix style file opening. For an existing file
> you want
> open("foo", O_flags)
>
> for a new file possibly
>
> open("foo", O_CREAT|o_flags, S_Iblah)
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: Write USB Device Driver entry not called

[Raj]

On Sat, 23 Oct 2004 07:12:56 +0530, eshwar <eshwar@moschip.com> wrote:
> I agree but the return value from the vfs_write should not be the -EBADF
> (Bad File descriptor) it might be -EACCES (premission denied)... Correct me
> if I am wrong...
> 
> this can be code in fs/read_write.c vfs_write()
> 
>  if (!(file->f_mode & FMODE_WRITE))
>   return -EACCES;

Wrong. You are confused between file perms & mode of access to files. 
If you cannot open a file due to insufficient perms, then EACCESS is
what you get.
If you opened a file for reading, but you tried to write, the you get a EBADF.

Run the following code, after you create two files, 'foo' ( perms 0400
) and 'bar' ( 0700 ).

#include <fcntl.h>

int main()
{
        int fd;

        fd = open("foo",O_WRONLY);

        if(fd < 0)
                perror("Opening foo:");
        else
                close (fd);

        fd = open("bar",O_RDONLY);

        if(fd < 0)
                perror("Opening bar: ");
        else {
                if(write(fd,'a',1) < 0)
                        perror("Write to bar failed: ");
                close(fd);
        }

}

Output would be:
Opening foo:: Permission denied
Write to bar failed: : Bad file descriptor
-- 
######
raj
######

Re: Write USB Device Driver entry not called

[eshwar]

if I modify the code like this

char abc;
                 if(read(fd,&abc,1) < 0)
                         perror("read to bar failed: ");
                 close(fd);

Which will be sucess... This intern states that my file descriptor is right
.... but write returns EBADF... both are contradicting statements....

Eshwar

----- Original Message -----
From: "Raj" <inguva@gmail.com>
To: "eshwar" <eshwar@moschip.com>
Cc: "Alan Cox" <alan@lxorguk.ukuu.org.uk>; "Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>
Sent: Thursday, October 14, 2004 9:09 AM
Subject: Re: Write USB Device Driver entry not called


> On Sat, 23 Oct 2004 07:12:56 +0530, eshwar <eshwar@moschip.com> wrote:
> > I agree but the return value from the vfs_write should not be the -EBADF
> > (Bad File descriptor) it might be -EACCES (premission denied)... Correct
me
> > if I am wrong...
> >
> > this can be code in fs/read_write.c vfs_write()
> >
> >  if (!(file->f_mode & FMODE_WRITE))
> >   return -EACCES;
>
> Wrong. You are confused between file perms & mode of access to files.
> If you cannot open a file due to insufficient perms, then EACCESS is
> what you get.
> If you opened a file for reading, but you tried to write, the you get a
EBADF.
>
> Run the following code, after you create two files, 'foo' ( perms 0400
> ) and 'bar' ( 0700 ).
>
> #include <fcntl.h>
>
> int main()
> {
>         int fd;
>
>         fd = open("foo",O_WRONLY);
>
>         if(fd < 0)
>                 perror("Opening foo:");
>         else
>                 close (fd);
>
>         fd = open("bar",O_RDONLY);
>
>         if(fd < 0)
>                 perror("Opening bar: ");
>         else {
>                 if(write(fd,'a',1) < 0)
>                         perror("Write to bar failed: ");
>                 close(fd);
>         }
>
> }
>
> Output would be:
> Opening foo:: Permission denied
> Write to bar failed: : Bad file descriptor
> --
> ######
> raj
> ######
> -
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

Re: Write USB Device Driver entry not called

[Raj]

On Thu, 21 Oct 2004 09:24:52 +0530, eshwar <eshwar@moschip.com> wrote:
> if I modify the code like this
> 
> char abc;
>                  if(read(fd,&abc,1) < 0)
>                          perror("read to bar failed: ");
>                  close(fd);
> 
> Which will be sucess... This intern states that my file descriptor is right
> .... but write returns EBADF... both are contradicting statements....

It's this simple. File was opened for Read-Only. So for vfs_read it is
a 'good' file
descriptor. And for vfs_write it is a 'BAD' file descriptor. 

-- 
######
raj
######