lkml.org 
[lkml]   [2005]   [Feb]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: gpio api
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 due to out-of-date or misconfigured drivers that would be prevented by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

--
He that composes himself is wiser than he that composes a book.
-- B. Franklin
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:10    [W:0.140 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site