Re: [PATCH 09/15] twl4030_charger: allow max_current to be managed via sysfs.

NeilBrown
2015-03-05T06:26:14Z

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On Mon, 2 Mar 2015 22:05:26 +0100 Pavel Machek <pavel@ucw.cz> wrote:

> On Tue 2015-02-24 15:33:52, NeilBrown wrote:
> > 'max_current' sysfs attributes are created which allow the
> > max to be set.
> > Whenever a current source changes, the default is restored.
> > This will be followed by a uevent, so user-space can decide to
> > update again.
>
> Does this need Documentation update?

Oh all right... I've created the relevant documentation in Documentation/ABI.

It seems persistence pays off :-)

>
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> > drivers/power/twl4030_charger.c | 76 +++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 76 insertions(+)
> >
> > diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c
> > index bfc9b808301e..b0242786d047 100644
> > --- a/drivers/power/twl4030_charger.c
> > +++ b/drivers/power/twl4030_charger.c
> > @@ -527,6 +529,67 @@ static irqreturn_t twl4030_bci_interrupt(int irq, void *arg)
> > return IRQ_HANDLED;
> > }
> >
> > +/*
> > + * sysfs max_current store
> > + */
>
> That's not exactly useful comment.

Now:

* Provide "max_current" attribute in sysfs.

>
> > +static ssize_t
> > +twl4030_bci_max_current_store(struct device *dev, struct device_attribute *attr,
> > + const char *buf, size_t n)
> > +{
> > + struct twl4030_bci *bci = dev_get_drvdata(dev->parent);
> > + int cur = 0;
> > + int status = 0;
> > + status = kstrtoint(buf, 10, &cur);
> > + if (status)
> > + return status;
> > + if (cur < 0)
> > + return -EINVAL;
> > + if (dev == bci->ac.dev) {
> > + if (bci->ac_cur == cur)
> > + return n;
> > + bci->ac_cur = cur;
> > + } else {
> > + if (bci->usb_cur == cur)
> > + return n;
> > + bci->usb_cur = cur;
> > + }
> > + twl4030_charger_update_current(bci);
> > + return (status == 0) ? n : status;
> > +}
>
> Uff. but we know that status == 0 at this point, no?

Yes. Fixed.

> Also... is
> optimalization of not calling update_current() when nothing changed
> worth it?

Probably not... and code looks a lot nicer if I remove that.
So I have.

>
> > +/*
> > + * sysfs max_current show
> > + */
> > +static ssize_t twl4030_bci_max_current_show(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + int status = 0;
> > + int cur = -1;
> > + u8 bcictl1;
> > + struct twl4030_bci *bci = dev_get_drvdata(dev->parent);
> > +
> > + if (dev == bci->ac.dev) {
> > + if (!bci->ac_is_active)
> > + cur = bci->ac_cur;
> > + } else {
> > + if (bci->ac_is_active)
> > + cur = bci->usb_cur;
> > + }
> > + if (cur < 0) {
> > + cur = twl4030bci_read_adc_val(TWL4030_BCIIREF1);
> > + if (cur < 0)
> > + return cur;
> > + status = twl4030_bci_read(TWL4030_BCICTL1, &bcictl1);
> > + if (status < 0)
> > + return status;
> > + cur = regval2ua(cur, bcictl1 & TWL4030_CGAIN);
> > + }
> > + return scnprintf(buf, PAGE_SIZE, "%u\n", cur);
> > +}
>
> Is this in uA or mA? uA. Ok.

uA, now described in Documentation/ABI/testing/sysfs-class-power-twl4030

+What: /sys/class/power_supply/twl4030_ac/max_current
+ /sys/class/power_supply/twl4030_usb/max_current
+Description:
+ Read/Write limit on current which which may
+ be drawn from the ac (Accessory Charger) or
+ USB port.
+
+ Value is in micro-Amps.
+
+ Value is set automatically to an appropriate
+ value when a cable is plugged on unplugged.
+
+ Value can the set by writing to the attribute.
+ The change will only persist until the next
+ plug event. These event are reported via udev.

>
> Acked-by: Pavel Machek <pavel@ucw.cz>
> Pavel
>

Thanks,
NeilBrown

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