[linux-dvb] Re: no pwm entry in sysfs

[Holger Waechtler <holger@qanu.de>]

Johannes Stezenbach wrote:

> Holger Waechtler wrote:
>  
> > Heikki Manninen wrote:
> >    
> > > So, wrong answer to my question: How should I be able to have the pwm
> > > entries for Fujitsu-Siemens DVB-C cards in sysfs?
> > >
> > > If there is no such way anymore, please let us know.
> > >      
> > As far I remember from the discussion on the linux-dvb mailing list this 
> > has been removed in the overhauling process because it unecessairily 
> > complicated the code and the proper solution is trivial to implement -- 
> > workarounds for broken EEPROMs that are easy to fix in userspace really 
> > don't belong in kernelspace.
> >    
> I don't remember such a discussion.
>
> My guess is that it was removed because frontend drivers aren't
> i2c_clients anymore, so there is no sysfs directory for them.
>  
you can directly write to any address on every i2c bus, you don't need 
any i2c client registered at all:

---- /usr/src/linux-2.6.XXX/Documentation/i2c/dev-interface
Next thing, open the device file, as follows:
 int file;
 int adapter_nr = 2; /* probably dynamically determined */
 char filename[20];

 sprintf(filename,"/dev/i2c-%d",adapter_nr);
 if ((file = open(filename,O_RDWR)) < 0) {
   /* ERROR HANDLING; you can check errno to see what went wrong */
   exit(1);
 }

When you have opened the device, you must specify with what device
address you want to communicate:
 int addr = 0x40; /* The I2C address */
 if (ioctl(file,I2C_SLAVE,addr) < 0) {
   /* ERROR HANDLING; you can check errno to see what went wrong */
   exit(1);
 }
----

For EEPROMs the i2c address is usually something between 0x50...0x55.

Holger