On Fri, 18 February 2005 08:46:08 -0500, Jamey Hicks wrote:
>
> GPIO Client Driver API
>
> The first two calls are analogous to request_irq/free_irq, so that
> driver can ensure that they have exclusive access to a GPIO and can
> specify asynchronous or synchronous access. I have run into problems
> due to out-of-date or misconfigured drivers that would be prevented by
> the use of these calls.
>
> #define GPIOF_SYNC (1 << 0)
> #define GPIOF_ASYNC (1 << 1)
> #define GPIOF_SYSFS (1 << 2)
> #define GPIOF_VALID (1 << 3)
>
> int request_gpio(int gpio_num, const char *name,
> void (*callback)(int gpionum, void *devid), int flags, void *devid);
> void free_gpio(int gpio_num, void *devid);
>
> It is a BUG to supply a NULL callback if GPIO is successfully
> requested with GPIOF_ASYNCH set. [Alternatively, split into sync and
> async calls and consider it a BUG to use the synchronous calls on a
> GPIO requested with GPIOF_ASYNC set.]
Don't split the interface. BUG_ON((flags&GPIOF_ASYNC) && !callback)
might be a good idea, but most likely there are valid reasons for NULL
callbacks as well.
Also, it's not unusual to request several pins at one. If the
requester can simply provide a bitmask, the calling code is *much*
simpler.
> int set_gpio_mode(int gpionum, int modeflags);
> int set_gpio_value(int gpionum, int value);
> int get_gpio_value(int gpionum);
These functions either lack a struct gpiochip argument or could be
omitted completely.
> GPIO Provider API
>
> struct gpiochip {
> int (*set)(struct gpiochip *chip, void *context, int value);
> int (*get)(struct gpiochip *chip void *context);
> int (*mode)(struct gpiochip *chip, void *context, int modeflags);
> };
A private structure is surely needed, no?
Overall, I like the idea. Having a standard interface for gpio
drivers makes life somewhat easier when writing a driver, and a *lot*
easier when using one. With every driver having their own custom
interface, some *will* end up broken and unusable.
J�rn
--
He that composes himself is wiser than he that composes a book.
-- B. Franklin
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