Re: [RESEND PATCH] iio: light: add support for TI's opt3001 light sensor

[Felipe Balbi <balbi@ti.com>]

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Hi,

On Sat, Sep 13, 2014 at 05:52:02PM +0100, Jonathan Cameron wrote:
> On 02/09/14 16:17, Felipe Balbi wrote:
> > TI's opt3001 light sensor is a simple and yet powerful
> > little device. The device provides 99% IR rejection,
> > Automatic full-scale, very low power consumption and
> > measurements from 0.01 to 83k lux.
> > 
> > This patch adds support for that device using the IIO
> > framework.
> > 
> > Signed-off-by: Felipe Balbi <balbi@ti.com>
> > ---
> > 
> > Resending as I saw no changes on the thread.
> Hi Felipe,
> 
> Sorry for the delay on this, entirely my fault - been busy and forgot
> I still had questions about what was going on in here (yup its the
> hysteresis bit again!)

right, this is starting to become way too much headache for such a
simple device. Sorry will not help me getting this driver upstream. When
I first sent this (August 6), we didn't even have v3.17-rc1, now we're
about to tag -rc5 and I'm worried this driver will not hit v3.18 merge
window.

> Anyhow, I'm afraid I am still a little confused about the meaning you
> have assigned to Hysteresis in this driver.
> 
> Let me conjecture on what might be going on here (I may be entirely
> wrong).
> 
> Normally a hysteresis value in IIO is defined as the 'distance' back
> from a threshold that a signal must go before it may retrip the
> threshold.
> This threshold value is separately controlled. Thus if we have a
> rising threshold of 10 and an hysteresis of 2 - to get two events the
> signal must first rise past 10, then drop back below 8 and rise again
> past 10.
> If it drops below 10 but not 8 and rises again past 10 then we will
> not get an event.
> 
> So having the same register for both the hysteresis and the threshold
> doesn't with this description make much sense.  It would mean that you
> could only have a threshold of say 10 and a hysteresis of 10, thus in
> effect meaning the signal would always have to cross 0 before the next
> event whatever the combined threshold / hysteresis value?
> 
> Perhaps instead the device is automatically adjusting the threshold
> when we cross it and the 'hysteresis' here is with respect to a the
> previous threshold?
> 
> Thus if we start with a value of 0 and hysteresis is set to 2 it will
> trigger an event at:
> 
> 2, 4, 6, 8, 10 as we rise?
> 
> This sort of auto adjustment of levels isn't uncommon in light sensors
> (where the point of the interrupt is to notify the operating system
> that a 'significant' change has occurred and things like screen
> brightness may need adjusting.
> 
> If so then the current hysteresis interface does not apply, nor does
> the Rate of Change (ROC) interface as this is dependent on amount of
> change, not how fast it changed.  Hence we needs something new to
> handle this cleanly. I would suggest a new event type.  Perhaps
> something with sysfs attr naming along the lines of
> What:		/sys/.../iio:deviceX/events/in_light_change_rising_en
> What:           /sys/.../iio:deviceX/events/in_light_change_rising_value
> 
> etc?

will you just tell me what you want ? I really cannot give a crap
anymore. This has already taken me over a month of my time for such a
simple little device, not to mention your confusing and contradicting
change requests.

(could you also trim your responses ? it's very annoying to scroll so
much)

> > +#define OPT3001_RESULT		0x00
> > +#define OPT3001_CONFIGURATION	0x01
> > +#define OPT3001_LOW_LIMIT	0x02
> > +#define OPT3001_HIGH_LIMIT	0x03
> > +#define OPT3001_MANUFACTURER_ID	0x7e
> > +#define OPT3001_DEVICE_ID	0x7f
> > +
> > +#define OPT3001_CONFIGURATION_RN_MASK (0xf << 12)
> > +#define OPT3001_CONFIGURATION_RN_AUTO (0xc << 12)
> > +
> > +#define OPT3001_CONFIGURATION_CT	BIT(11)
> > +
> > +#define OPT3001_CONFIGURATION_M_MASK	(3 << 9)
> > +#define OPT3001_CONFIGURATION_M_SHUTDOWN (0 << 9)
> > +#define OPT3001_CONFIGURATION_M_SINGLE (1 << 9)
> > +#define OPT3001_CONFIGURATION_M_CONTINUOUS (2 << 9) /* also 3 << 9 */
> > +
> 
> I guess this naming is straight off the datasheet, but it is rather
> more cryptic than perhaps it needs to be!  That's kind of an issue
> with the datasheet choices rather than what you have here however!

man, are you nit-picky!! These are named as such to make grepping on
documentation easier. It's better to have something that matches
documentation, don't you think ? otherwise, future users/developers of
these driver will need either a shit ton of comments explaining that A
maps to B in docs, or will need a fscking crystal ball to read my mind.
Assuming I'll still remember what I meant.

> > +static int opt3001_remove(struct i2c_client *client)
> > +{
> > +	struct iio_dev *iio = i2c_get_clientdata(client);
> > +	struct opt3001 *opt = iio_priv(iio);
> > +	int ret;
> > +	u16 reg;
> > +
> > +	free_irq(client->irq, iio);
> > +	iio_device_unregister(iio);
> > +
> > +	ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
> > +	if (ret < 0) {
> > +		dev_err(opt->dev, "failed to read register %02x\n",
> > +				OPT3001_CONFIGURATION);
> > +		return ret;
> > +	}
> > +
> > +	reg = ret;
> > +	opt3001_set_mode(opt, &reg, OPT3001_CONFIGURATION_M_SHUTDOWN);
> > +
> > +	ret = i2c_smbus_write_word_swapped(opt->client, OPT3001_CONFIGURATION,
> > +			reg);
> > +	if (ret < 0) {
> > +		dev_err(opt->dev, "failed to write register %02x\n",
> > +				OPT3001_CONFIGURATION);
> > +		return ret;
> > +	}
> > +
> > +	iio_device_free(iio);
>
> Use the devm_iio_device_alloc and you can drop the need to free it.
> I don't really mind, but I'll almost guarantee that someone will post
> a follow up patch doing this if you don't.  As it will be ever so
> slightly cleaner, I'll probably take that patch.

here's the original driver:

http://www.spinics.net/lists/linux-iio/msg14331.html

notice that it *WAS* *USING* devm_iio_device_alloc(), until:

http://www.spinics.net/lists/linux-iio/msg14421.html

you *SPECIFICALLY* asked for *NON* *DEVM* versions!!

So figure out what you really want, let me know and I'll code it all up
quickly and hopefully still get this into v3.18 merge window. I sent
this driver *very* early to be doubly sure it would hit v3.18 and there
was a long hiatus from yourself which is now jeopardizing what I was
expecting. That, coupled with your contradicting requests, has just put
me in a bad mood, even before Monday, hurray.

cheers

-- 
balbi

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