lkml.org 
[lkml]   [2008]   [Sep]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [patch 2.6.27-rc7] gpiolib: request/free hooks
Hi David,

On Thu, Sep 25, 2008 at 7:08 AM, David Brownell <david-b@pacbell.net> wrote:
> From: David Brownell <dbrownell@users.sourceforge.net>
>
> Add a new internal mechanism to gpiolib to support low power
> operations by letting gpio_chip instances see when their GPIOs
> are in use. When no GPIOs are active, chips may be able to
> enter lower powered runtime states by disabling clocks and/or
> power domains.
>
> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

Looking good. I'm currently hacking on some pinmuxed gpio code for
SuperH, and I'd like to use these request/free callbacks to select
proper pinmux state.

I have one comment below though:

> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -781,6 +785,7 @@ EXPORT_SYMBOL_GPL(gpiochip_remove);
> int gpio_request(unsigned gpio, const char *label)
> {
> struct gpio_desc *desc;
> + struct gpio_chip *chip;
> int status = -EINVAL;
> unsigned long flags;
>
> @@ -789,22 +794,31 @@ int gpio_request(unsigned gpio, const ch
> if (!gpio_is_valid(gpio))
> goto done;
> desc = &gpio_desc[gpio];
> - if (desc->chip == NULL)
> + chip = desc->chip;
> + if (chip == NULL)
> goto done;
>
> - if (!try_module_get(desc->chip->owner))
> + if (!try_module_get(chip->owner))
> goto done;
>
> /* NOTE: gpio_request() can be called in early boot,
> - * before IRQs are enabled.
> + * before IRQs are enabled, for non-sleeping (SOC) GPIOs.
> */
>
> + if (chip->request) {
> + status = chip->request(chip, gpio - chip->base);
> + if (status < 0) {
> + module_put(chip->owner);
> + goto done;
> + }
> + }
> +
> if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
> desc_set_label(desc, label ? : "?");
> status = 0;
> } else {
> status = -EBUSY;
> - module_put(desc->chip->owner);
> + module_put(chip->owner);
> }
>
> done:

The code above doesn't catch double gpio_request() user calls
properly. Or rather, the user will receive an error but the
chip->request() callback may get called twice.

What about modifying the gpiolib code to handle that? I think that
sounds like a better idea than cover ing that case in the chip code...

Thanks!

/ magnus


\
 
 \ /
  Last update: 2008-09-27 17:03    [W:0.046 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site