Re: [PATCH RFC 02/15 v5] gpio: Add sysfs support to block GPIO API

Greg KH
2012-10-17T19:05:26Z

On Wed, Oct 17, 2012 at 02:31:34PM +0200, Roland Stigge wrote:
> This patch adds sysfs support to the block GPIO API.
>
> Signed-off-by: Roland Stigge <stigge@antcom.de>
>
> ---
> Documentation/ABI/testing/sysfs-gpio | 6
> drivers/gpio/gpiolib.c | 214 +++++++++++++++++++++++++++++++++++
> include/asm-generic/gpio.h | 11 +
> include/linux/gpio.h | 13 ++
> 4 files changed, 243 insertions(+), 1 deletion(-)
>
> --- linux-2.6.orig/Documentation/ABI/testing/sysfs-gpio
> +++ linux-2.6/Documentation/ABI/testing/sysfs-gpio
> @@ -24,4 +24,8 @@ Description:
> /base ... (r/o) same as N
> /label ... (r/o) descriptive, not necessarily unique
> /ngpio ... (r/o) number of GPIOs; numbered N to N + (ngpio - 1)
> -
> + /blockN ... for each GPIO block #N
> + /ngpio ... (r/o) number of GPIOs in this group
> + /exported ... sysfs export state of this group (0, 1)
> + /value ... current value as 32 or 64 bit integer in decimal
> + (only available if /exported is 1)

I think you need some more documentation here, as I just noticed
something "odd":

> +static int gpio_block_value_unexport(struct gpio_block *block)
> +{
> + struct device *dev;
> + int i;
> +
> + dev = class_find_device(&gpio_block_class, NULL, block, match_export);
> + if (!dev)
> + return -ENODEV;
> +
> + for (i = 0; i < block->ngpio; i++)
> + gpio_free(block->gpio[i]);
> +
> + device_remove_file(dev, &dev_attr_block_value);
> +
> + return 0;
> +}

Wait, what? You are removing a sysfs file in this function, from within
a sysfs write:

> +static ssize_t gpio_block_exported_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + long value;
> + int status;
> + struct gpio_block *block = dev_get_drvdata(dev);
> + int exported = gpio_block_value_is_exported(block);
> +
> + status = kstrtoul(buf, 0, &value);
> + if (status < 0)
> + goto err;
> +
> + if (value != exported) {
> + if (value)
> + status = gpio_block_value_export(block);
> + else
> + status = gpio_block_value_unexport(block);

That looks like a recipie for disaster. Why do you allow userspace to
do this?

Anyway, the other fixups for how you create/destroy the attribute files
looks great, thanks for making those changes.

greg k-h