linux-kernel - Re: [PATCH] drivers: create a pin control subsystem v8

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Message-ID: <CACRpkdYyyqB6=5M8reqgwpMxXJz5ttXWyOav6K58dQ0CrxwCNA@mail.gmail.com>
Date:	Fri, 30 Sep 2011 17:05:20 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	Linus Walleij <linus.walleij@...ricsson.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Barry Song <21cnbao@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Joe Perches <joe@...ches.com>,
	Russell King <linux@....linux.org.uk>,
	Linaro Dev <linaro-dev@...ts.linaro.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	David Brown <davidb@...eaurora.org>,
	Stijn Devriendt <highguy@...il.com>
Subject: Re: [PATCH] drivers: create a pin control subsystem v8

On Fri, Sep 30, 2011 at 4:07 AM, Grant Likely <grant.likely@...retlab.ca> wrote:

> Comments below, some a bit nitpicky, but overall I think it looks
> good.  I haven't dug into it nearly deeply enough though.  :-(

Hopefully we can patch the remaining bugs as we go along  :-)

>> +/**
>> + * Looks up a pin control device matching a certain device name or
>> + * pure device pointer.
>
> May as well actually do kerneldoc formatting here on the comment
> blocks.

OK.

>> +struct pinctrl_dev *get_pctldev_from_dev(struct device *dev,
>> +                                      const char *devname)
>
> Nit: I'm not too fond of a single function doing both name and pointer
> lookup at the same time.  Presumably the caller would have one or the
> other and know what it needs to do.  I'd prefer to see one by-name
> function and one by-reference.  I'm not going to make a big deal about
> it though.

The caller currently does not know what it has or
what to do.

This is basically an interator function that is called on
a member tuple of device and device name to check
which one you have and return a matching controller
device for the key you do have.

>> +     /* Register device with sysfs */
>> +     pctldev->dev.parent = dev;
>> +     pctldev->dev.bus = &pinctrl_bus;
>
> I don't think there is an actual need for a pinctrl bus type.  There
> aren't any drivers that are going to be bound to these things which is
> the primary functionality that a bus type provides.  Am I missing
> something?

That is not the reason it's there actually, what we have
discussed on the mailing list is getting sysfs entries for the same
reason gpiolib registers a class: handle pin control from userspace,
we can already see that coming and I already have a use case
for it. (Modem SIM connector control from userspace daemon.)

So first it was registering a class, then Greg said classes are
deprecated and we should use a bus instead. So it is
registering a bus to get sysfs so we can get userspace
controls.

>> +out_err:
>> +     put_device(&pctldev->dev);
>> +     kfree(pctldev);
>
> Once a device is initialized, it cannot be kfree()'ed directly.  The
> .release method needs to do that.

OK. And I already had a proper .release() method doing
exactly that, so deleting this.

>> +/**
>> + * pin_free() - release a single muxed in pin so something else can be muxed in
>> + *   instead
>
> Nit: the summary line in kerneldoc should fit on one line.

OK.

Went over the code and fixed a few other sites too.

>> +int __init
>> +pinmux_register_mappings(struct pinmux_map const *maps, unsigned num_maps)
>
> Nit: keep line breaks in the parameter lists.  More grep friendly.

OK fixed it.

Yours,
Linus Walleij
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