linux-kernel - Re: [PATCH 1/4 v4] drivers: create a pin control subsystem

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Date:	Fri, 2 Sep 2011 09:02:32 +0200
From:	Stijn Devriendt <highguy@...il.com>
To:	Linus Walleij <linus.walleij@...ricsson.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Lee Jones <lee.jones@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	Joe Perches <joe@...ches.com>,
	Russell King <linux@....linux.org.uk>,
	Linaro Dev <linaro-dev@...ts.linaro.org>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH 1/4 v4] drivers: create a pin control subsystem

On Fri, Aug 19, 2011 at 11:53 AM, Linus Walleij
<linus.walleij@...ricsson.com> wrote:
> +
> +/**
> + * pin_request() - request a single pin to be muxed in, typically for GPIO
> + * @pin: the pin number in the global pin space
> + * @function: a functional name to give to this pin, passed to the driver
> + *     so it knows what function to mux in, e.g. the string "gpioNN"
> + *     means that you want to mux in the pin for use as GPIO number NN
> + * @gpio: if this request concerns a single GPIO pin
> + */
> +static int pin_request(struct pinctrl_dev *pctldev,
> +                      int pin, const char *function, bool gpio)
> +{
> +       struct pin_desc *desc;
> +       const struct pinmux_ops *ops;
> +       int status = -EINVAL;
> +
> +       pr_debug("request pin %d for %s\n", pin, function);
> +
> +       if (!pin_is_valid(pctldev, pin)) {
> +               pr_err("pin is invalid\n");
> +               return -EINVAL;
> +       }
> +
> +       if (!function) {
> +               pr_err("no function name given\n");
> +               return -EINVAL;
> +       }
> +
> +       desc = pin_desc_get(pctldev, pin);
> +       if (desc == NULL) {
> +               pr_err("pin is not registered so it cannot be requested\n");
> +               goto out;
> +       }
> +       if (desc->mux_requested) {
> +               pr_err("pin already requested\n");
> +               goto out;
> +       }

Isn't locking missing here?

> +       ops = pctldev->desc->pmxops;
> +
> +       /* Let each pin increase references to this module */
> +       if (!try_module_get(pctldev->owner)) {
> +               pr_err("could not increase module refcount for pin %d\n", pin);
> +               status = -EINVAL;
> +               goto out;
> +       }
> +
> +       /*
> +        * If there is no kind of request function for the pin we just assume
> +        * we got it by default and proceed.
> +        */
> +       if (gpio && ops->gpio_request_enable)
> +               /* This requests and enables a single GPIO pin */
> +               status = ops->gpio_request_enable(pctldev, pin);
> +       else if (ops->request)
> +               status = ops->request(pctldev, pin);
> +       else
> +               status = 0;
> +
> +       if (status) {
> +               pr_err("->request on device %s failed "
> +                      "for pin %d\n",
> +                      pctldev->desc->name, pin);
> +               goto out;
> +       }
> +
> +       desc->mux_requested = true;
> +       strncpy(desc->mux_function, function, sizeof(desc->mux_function));
> +
> +out:
> +       if (status)
> +               pr_err("pin-%d (%s) status %d\n",
> +                      pin, function ? : "?", status);
> +
> +       return status;
> +}
> +

Regards,
Stijn
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