Re: [patch 2.6.21-rc1] pxa2xx_udc: use generic gpio layer

On Wednesday 28 February 2007 6:36 am, Milan Svoboda wrote:
> On Monday 26 February 2007 5:35 am, Milan Svoboda wrote:
> 
> > > There is one problem, thought. Original code used:
> > > 
> > > static inline void udc_gpio_init_pullup(unsigned gpio)
> > > {
> > >        pxa_gpio_mode((gpio & GPIO_MD_MASK_NR) | GPIO_OUT | 
> GPIO_DFLT_LOW);
> > > }
> > > 
> > > But new generic gpio doesn't allows us to specify GPIO_DFLT_LOW. I'm 
> not 
> > > sure if this is a problem. Any thoughts?
> > 
> > Specifically here, not a problem ...
> > 
> > In general, that's a potential problem.  Not including a default
> > value for gpio_direction_output() was an oversight, and that should
> > probably get fixed before 2.6.21-final.  Andrew Victor raised that
> > issue offline in the context of AT91 (and AVR32).
> > 
> > If you felt like fixing that for the ixp4xx and pxa, I expect that
> > fixes could soon be forthcoming for other platforms and the docs.
> > 
> 
> How to fix it?
> 
> ...
> 2. Change the gpio_direction_output(int gpio) to
>    gpio_direction_output(int gpio, int level) and let the user to decide
>    if he want's low or high level?
> 
> What's preferable?

Only #2 can ensure there's never a glitch.  The boot firmware may
have set up a particular after-reset value; the GPIO controller may
reset to low or high depending on its implementation (likely high
via internal pullup, and configured as input, for power savings);
so another argument is needed.

- Dave

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