Messages in this thread | | | Date | Fri, 18 Feb 2005 15:35:17 +0100 | From | Jörn Engel <> | Subject | Re: gpio api |
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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 due to out-of-date or misconfigured drivers that would be prevented by 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.
Jörn
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