I get errno 13 when I try and open the /dev/i2c-0 special character
file that gets created on insmod i2c-0.ko.
errno=0;
file = open("/dev/i2c-0", O_RDWR);
if(file < 0) {
return errno;
}
The above code returns with errno as 13.
Any ideas as to why?
Thanks!
On Nov 11, 9:38 am, Pubudu <[email protected]> wrote:
> I think what you are referring as error code being -1 is the return
> code of ioctl being -1.
> check the value of 'errno' at that point against the error.h
>
> regards..
>
> On Nov 11, 3:01 am, shootingatshadow <[email protected]>
> wrote:
>
> > Ok so, I grabbed the kernel source, built and installed kernel with
> > loadable module support and had it built the i2c modules. I then
> > insmod the i2c-dev.ko and it worked fine. It created a character
> > special file 89 0 under /dev/i2c-0.
>
> > I can open the file just fine with file = open("/dev/i2c-0", O_RDWR),
> > however the ioctl(file, I2C_SLAVE, address) fails with error code -1.
> > I looked at (i think) error.h and all errors were positive. I have not
> > been able to find a list of ioctl error codes, nor do I know what I am
> > doing wrong here.
>
> > Also, a big thanks to everyone here, you pointed me in the right
> > direction and helped me out!
>
> > On Oct 30, 7:18 am, Deva R <[email protected]> wrote:
>
> > > now, what exactly is the blocking issue?
>
> > > On Wed, Oct 27, 2010 at 10:30 PM, shootingatshadow <
>
> > > [email protected]> wrote:
> > > > Thanks for your help, I spent the last few weeks doing more research
> > > > and am still stuck.
>
> > > > 1.) I went to The Linux Documentation Project, and was unable to find
> > > > anything on I2C development, any suggestions on where to go would be
> > > > appreciated.
>
> > > its right in ./Documentation/i2c folder.. did u miss more than
> > > that?http://lxr.linux.no/linux+v2.6.36/Documentation/i2c/dev-interface
>
> > > > 2.) My second question, is that the i2c-dev.h header, which from my
> > > > understanding is required for user space i2c access, is distributed in
> > > > the lm-sensors project for Debian based systems. Is their an
> > > > alternative for an Arm based Android system?
>
> > > <linux/*.h> are generic headers which are platform agnostic..
> > > if at all a header is architecture specific (say cpu.h, cache.h) - goes
> > > into
> > > arch/x86/include/asm/, arch/arm/include/asm/
>
> > > only platform specific driver implementation goes under
> > > ./arch/arm/<>/<i2c>
>
> > > > Thanks again!
>
> > > > On Oct 13, 2:15 am, kavitha bk <[email protected]> wrote:
> > > > > Hi,
> > > > > U can go through Linux Documentation for i2c
> > > > > Plain I2C communication
> > > > > -----------------------
> > > > > int i2c_master_send(struct i2c_client *client, const char
> > > > > *buf,
> > > > > int count);
> > > > > int i2c_master_recv(struct i2c_client *client, char *buf, int
> > > > > count);
> > > > > These routines read and write some bytes from/to a client. The client
> > > > > contains the i2c address, so you do not have to include it. The second
> > > > > parameter contains the bytes to read/write, the third the number of
> > > > > bytes
> > > > > to read/write (must be less than the length of the buffer.) Returned
> > > > > is
> > > > > the actual number of bytes read/written.
> > > > > int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg
> > > > > *msg,
> > > > > int num);
> > > > > This is if u r doing from kernel.
>
> > > > > If u want to communicate to a i2c device from user space
>
> > > > > I2C device files are character device files with major device number
> > > > > 89 and a minor device number corresponding to the number assigned as
> > > > > explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ...,
>
> > > > > i2c-10, ...). All 256 minor device numbers are reserved for i2c.
>
> > > > > Usually, i2c devices are controlled by a kernel driver. But it is also
> > > > > possible to access all devices on an adapter from userspace, through
> > > > > the /dev interface. You need to load module i2c-dev for this.
>
> > > > > Each registered i2c adapter gets a number, counting from 0. You can
> > > > > examine /sys/class/i2c-dev/ to see what number corresponds to which
> > > > > adapter.
>
> > > > > int file = open(/dev/i2c-0, O_RDWR);
>
> > > > > When you have opened the device, you must specify with what device
> > > > > address you want to communicate:
>
> > > > > int addr = 0x40; /* The I2C address */
>
> > > > > ioctl(file, I2C_SLAVE, addr)
>
> > > > > Then u can communicate with the device
>
> > > > > Regards,
>
> > > > > Kavitha
>
> > > > > On Tue, Oct 12, 2010 at 5:42 PM, shootingatshadow <
> > > > [email protected]
>
> > > > > > wrote:
> > > > > > I am a bit new to Linux device drivers, been doing some research and
> > > > > > trying things out. (Read Linux Device Drivers Book, digging around
> > > > > > forums)
>
> > > > > > So I have found at i2c address 0x38 a chip which I would like to
> > > > > > talk
> > > > > > to. There is already a driver in place for that chip. I have the
> > > > > > spec
> > > > > > sheet in hand for that chip as well. However, the device shows up
> > > > > > under /proc/bus and in the devices file. How can I access this
> > > > > > device
> > > > > > and send it information? My only other experience is opening a file
> > > > > > under /dev/DEVICE and read and write bytes to it, any suggestions
> > > > > > would be greatly appreciated.
>
> > > > > > --
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>
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>
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>
> > > --
> > > Regards,
> > > Devawww.bittoggler.com
>
>
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