Re: pca953x GPIO

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

On Thu, 24 Jun 2010 19:49:00 +0200, Giampaolo Bellini wrote:
> Hello Jean
> 
>   thanks you so much for your time!
> 
> > This means they refer to left-aligned addresses. Linux uses
> > right-aligned addresses, so your device lives at 0x20 as far as Linux
> > is concerned.
> 
> effectively, after hours and hours of testing, I found by myself that
> the correct addressed where 0x20 and 0x21 but was not able to

Just 0x20, not "0x20 and 0x21". The "address byte" that goes on the
wire is made of 7 bits of address and 1 bit of direction (read or
write). 0x40 is (0x20 << 1) | 0, 0x41 is (0x20 << 1) | 1.

> understand why the manufacturer gives me what I think was a wrong
> registers map !

These are device addresses, nothing to do with a "register map".

> > Check arch/arm/mach-ks8695/board-acs5k.c and
> > arch/arm/mach-pxa/cm-x300.c for examples.
> 
> I'll check these source in the next days... so pca953x driver could
> just export his services to other modules ? does it nothing alone
> and/or paired with gpiolib ? or it's just a question of give the
> pca953x some platforms data ?

It is indeed just a question of instantiating the pca953x device with
some platform data.

> > (Assuming i2c-0 is the bus on which the chip actually lives - you can
> > check with i2cdetect). That being said, I doubt that a GPIO chip can
> > really be instantiated from user-space, as it needs configuration
> > settings which you can't provide that way.
> 
> you are right... i've try yesterday with the correct addresses but
> with no success.

-- 
Jean Delvare