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

[Linus Walleij]

On Thu, Oct 18, 2012 at 12:07 PM, Roland Stigge <stigge@xxxxxxxxx> wrote:
> On 10/17/2012 09:05 PM, Greg KH wrote:
>>>
>>> +    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?
>
> Exporting for gpio blocks is done as follows: writing "1" to the
> "exported" _device_ attribute of the gpio block creates the "values"
> attribute and at the same time requests the whole block (including all
> of its gpios) as "sysfs".

To me it reads like Greg's comment is basically pinpointing a flaw
in Brownell's initial design of gpio sysfs: that new sysfs files are
created and destroyed by writing into sysfs */export files from
userspace?

See commit: d8f388d8dc8d4f36539dd37c1fff62cc404ea0fc

The block GPIO stuff is just following that design pattern.

Yours,
Linus Walleij
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