On Mon, Mar 28, 2016 at 11:12 AM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
> On 24/03/16 13:18, Linus Walleij wrote:
>> +- st,int-pin-open-drain: the interrupt/data ready line will be configured
>> + as open drain, which is useful if several sensors share the same
>> + interrupt line.
>
> Really feels like this one ought to be more generic.. Mind you so does
> drdy-int-pin!
Sorry about drdy-int-pin, it wasn't me ;)
That one is a mux kind of thing: interrupt goes out on IRQ line
INT1 or INT2, select one...
> Hmm. Looks like most open drain controls are chip specific - other than
> your pinctrl ones and that doesn't really map to here I guess.
Both the muxing and the OD setting can be done with pin control,
it's just that it is like swatting a fly with a skyscraper - vast overkill
for two interrupt lines.
I came to the conclusion that with small chips or IP blocks just
randomly doing some muxing or biasing of a few pins isn't necessarily
worth all the trouble of implementing pin control, the latter was
conceived for real big arrays of pins really. There are already a
few of these all over the kernel, e.g. the ST Multi-Purpose expander
drivers/mfd/stmpe.c - could be pin control muxed but it'd be overkill.
So as pin control maintainer when this kind of hardware comes up
I usually just "think it over" and then "OK then".
>> + if (sdata->int_pin_open_drain) {
>> + dev_info(&indio_dev->dev,
>> + "set interrupt line to open drain mode\n");
>
> Hmm. Curriously I have a board with an lis3l02dq on it where the interrupt
> is shared, but doesn't explicitly support open drain. In that case it
> is done with some external circuitry.
That should run fine with just the status read patch from earlier
in the series I guess?
> Anyhow - I guess when I actually add support for that I'll just add a sanity
> check in here that addr_od and mask_od are specified :)
Hm, yeah. Otherwise just patch out my enforcement of the
OD flag for a shared line and add a comment in.
Yours,
Linus Walleij
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