Re: [PATCH 10/20] gpio: pca953x: Add optional reset gpio control

From: Steve Longerbeam
Date: Fri Dec 30 2016 - 13:04:02 EST

Hi Linus, Lothar,

On 12/30/2016 05:17 AM, Linus Walleij wrote:
On Thu, Dec 29, 2016 at 11:27 PM, Steve Longerbeam
<slongerbeam@xxxxxxxxx> wrote:

Add optional reset-gpios pin control. If present, de-assert the
specified reset gpio pin to bring the chip out of reset.

Signed-off-by: Steve Longerbeam <steve_longerbeam@xxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
Cc: Alexandre Courbot <gnurou@xxxxxxxxx>
Cc: linux-gpio@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
This seems like a separate patch from the other 19 patches so please send it
separately so I can handle logistics easier in the future.

Ok, I'll send the next version separately.

@@ -133,6 +134,7 @@ struct pca953x_chip {
const char *const *names;
unsigned long driver_data;
struct regulator *regulator;
+ struct gpio_desc *reset_gpio;
Why do you even keep this around in the device state container?

As you only use it in the probe() function, use a local variable.

The descriptor will be free():ed by the devm infrastructure anyways.

I think my reasoning for putting the gpio handle into the device
struct was for possibly using it for run-time reset control at some
point. But that could be done later if needed, so I'll go ahead and
make it local.

+ /* see if we need to de-assert a reset pin */
+ chip->reset_gpio = devm_gpiod_get_optional(&client->dev,
+ "reset",
+ if (IS_ERR(chip->reset_gpio)) {
+ dev_err(&client->dev, "request for reset pin failed\n");
+ return PTR_ERR(chip->reset_gpio);
+ }

+ if (chip->reset_gpio) {
+ /* bring chip out of reset */
+ dev_info(&client->dev, "releasing reset\n");
+ gpiod_set_value(chip->reset_gpio, 0);
+ }
Is this really needed given that you set it low in the

Yep, this is left over from a previous iteration, but it isn't needed now.
I'll remove it.