Re: [PATCH v2 08/12] gpio: add ti-ssp virtual gpio driver

[Cyril Chemparathy <cyril-l0cyMroinI0@public.gmane.org>]

Hi David,

On 10/21/2010 06:41 PM, David Brownell wrote:
> On Mon, 2010-10-18 at 15:25 -0400, Cyril Chemparathy wrote:
>> This patch adds a GPIO driver based on TI's SSP device.  This driver does not
>> support GPIO-IRQs.
> 
> Doesn't look particularly evil, except I don't much like the notion of
> needing a "stack" if it's not being used like an MFD where numerous
> functions are accessed concurrently, better IMO to just have each
> function's driver bind exclusively to the chip (and drive it in the
> mode it supports -- SPI, GPIO etc).

SPI and GPIO are not the only modes that this hardware can be programmed
to behave in.  In future, other functions may be added as needed.  I
thought it would be best to keep the shared stuff reusable.

> Also, the patch description is weak/confusing.  First, there's not a
> thing "virtual" about this.  Second, just say that this GPIO driver is
> bypassing pretty much everything in the SSP module (notably, all the
> silicon support for serial protocols) and just driving some of the
> pins as GPIOs.  (Right?)

Sure.

[...]
>> +config GPIO_TI_SSP
>> +	tristate "TI SSP Controller GPIO Driver"
>> +	depends on GPIOLIB && TI_SSP
>> +	help
>> +	  Say yes here to support a virtual GPIO interface on TI SSP ports.
>> +	  Each SSP port translates into 4 GPIOs, with no IRQ support.
> 
> Don't emphasize the "no IRQ part so much; lots of GPIOs don't do IRQs.
> If a board uses SSP this way, it won't care; Kconfig users have no
> control over such board wiring issues.

Agreed.

Thanks
Cyril.