Re: [PATCH v7 05/12] mux: support simplified bindings for single-user gpio mux

[Jonathan Cameron <jic23@kernel.org>]

On 08/01/17 21:56, Peter Rosin wrote:
> On 2017-01-08 11:28, Jonathan Cameron wrote:
>> On 05/01/17 16:21, Peter Rosin wrote:
>>> On 2017-01-04 13:16, Peter Rosin wrote:
>>>> Signed-off-by: Peter Rosin <peda@axentia.se>
>>>> ---
>>>>  drivers/mux/mux-core.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++--
>>>>  drivers/mux/mux-gpio.c | 56 ++--------------------------------
>>>>  include/linux/mux.h    |  7 +++++
>>>>  3 files changed, 89 insertions(+), 55 deletions(-)
>>>>
>>>> diff --git a/drivers/mux/mux-core.c b/drivers/mux/mux-core.c
>>>> index 21da15a264ad..d887ae1c0e55 100644
>>>> --- a/drivers/mux/mux-core.c
>>>> +++ b/drivers/mux/mux-core.c
>>>> @@ -15,6 +15,7 @@
>>>>  #include <linux/device.h>
>>>>  #include <linux/err.h>
>>>>  #include <linux/idr.h>
>>>> +#include <linux/gpio/consumer.h>
>>>>  #include <linux/module.h>
>>>>  #include <linux/mux.h>
>>>>  #include <linux/of.h>
>>>> @@ -288,6 +289,63 @@ static struct mux_chip *of_find_mux_chip_by_node(struct device_node *np)
>>>>  	return dev ? to_mux_chip(dev) : NULL;
>>>>  }
>>>>  
>>>> +#ifdef CONFIG_MUX_GPIO
>>>> +
>>>> +static int mux_gpio_set(struct mux_control *mux, int state)
>>>> +{
>>>> +	struct mux_gpio *mux_gpio = mux_chip_priv(mux->chip);
>>>> +	int i;
>>>> +
>>>> +	for (i = 0; i < mux_gpio->gpios->ndescs; i++)
>>>> +		mux_gpio->val[i] = (state >> i) & 1;
>>>> +
>>>> +	gpiod_set_array_value_cansleep(mux_gpio->gpios->ndescs,
>>>> +				       mux_gpio->gpios->desc,
>>>> +				       mux_gpio->val);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static const struct mux_control_ops mux_gpio_ops = {
>>>> +	.set = mux_gpio_set,
>>>> +};
>>>> +
>>>> +struct mux_chip *mux_gpio_alloc(struct device *dev)
>>>> +{
>>>> +	struct mux_chip *mux_chip;
>>>> +	struct mux_gpio *mux_gpio;
>>>> +	int pins;
>>>> +	int ret;
>>>> +
>>>> +	pins = gpiod_count(dev, "mux");
>>>> +	if (pins < 0)
>>>> +		return ERR_PTR(pins);
>>>> +
>>>> +	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux_gpio) +
>>>> +				       pins * sizeof(*mux_gpio->val));
>>>> +	if (!mux_chip)
>>>> +		return ERR_PTR(-ENOMEM);
>>>> +
>>>> +	mux_gpio = mux_chip_priv(mux_chip);
>>>> +	mux_gpio->val = (int *)(mux_gpio + 1);
>>>> +	mux_chip->ops = &mux_gpio_ops;
>>>> +
>>>> +	mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW);
>>>> +	if (IS_ERR(mux_gpio->gpios)) {
>>>> +		ret = PTR_ERR(mux_gpio->gpios);
>>>> +		if (ret != -EPROBE_DEFER)
>>>> +			dev_err(dev, "failed to get gpios\n");
>>>> +		return ERR_PTR(ret);
>>>> +	}
>>>> +	WARN_ON(pins != mux_gpio->gpios->ndescs);
>>>> +	mux_chip->mux->states = 1 << pins;
>>>> +
>>>> +	return mux_chip;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(mux_gpio_alloc);
>>>> +
>>>> +#endif /* CONFIG_MUX_GPIO */
>>>> +
>>>>  struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
>>>>  {
>>>>  	struct device_node *np = dev->of_node;
>>>> @@ -307,9 +365,28 @@ struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
>>>>  	ret = of_parse_phandle_with_args(np,
>>>>  					 "mux-controls", "#mux-control-cells",
>>>>  					 index, &args);
>>>> +
>>>> +#ifdef CONFIG_MUX_GPIO
>>>> +	if (ret == -ENOENT && !mux_name && gpiod_count(dev, "mux") > 0) {
>>>> +		mux_chip = mux_gpio_alloc(dev);
>>>> +		if (!IS_ERR(mux_chip)) {
>>>> +			ret = devm_mux_chip_register(dev, mux_chip);
>>>> +			if (ret < 0) {
>>>> +				dev_err(dev, "failed to register mux-chip\n");
>>>> +				return ERR_PTR(ret);
>>>> +			}
>>>> +			get_device(&mux_chip->dev);
>>>> +			return mux_chip->mux;
>>>> +		}
>>>> +
>>>> +		ret = PTR_ERR(mux_chip);
>>>> +	}
>>>> +#endif
>>>> +
>>>>  	if (ret) {
>>>> -		dev_err(dev, "%s: failed to get mux-control %s(%i)\n",
>>>> -			np->full_name, mux_name ?: "", index);
>>>> +		if (ret != -EPROBE_DEFER)
>>>> +			dev_err(dev, "%s: failed to get mux-control %s(%i)\n",
>>>> +				np->full_name, mux_name ?: "", index);
>>>>  		return ERR_PTR(ret);
>>>>  	}
>>>>  
>>>> diff --git a/drivers/mux/mux-gpio.c b/drivers/mux/mux-gpio.c
>>>> index 76b52bc63470..8a7bfbc0c4bb 100644
>>>> --- a/drivers/mux/mux-gpio.c
>>>> +++ b/drivers/mux/mux-gpio.c
>>>> @@ -11,37 +11,12 @@
>>>>   */
>>>>  
>>>>  #include <linux/err.h>
>>>> -#include <linux/gpio/consumer.h>
>>>>  #include <linux/module.h>
>>>>  #include <linux/mux.h>
>>>>  #include <linux/of_platform.h>
>>>>  #include <linux/platform_device.h>
>>>>  #include <linux/property.h>
>>>
>>> Instead of moving the mux-gpio guts from mux-gpio.c to mux-core.c, I
>>> will instead make CONFIG_MUX_GPIO a bool option (no module possible)
>>> and call it from the mux-core. That will be cleaner and less of a
>>> break of abstractions in my opinion.
>> Hmm. I wonder if the balance is right here or whether we should just not have the
>> simplified binding at all as it breaks the assumption that all muxes are of the
>> same level...
>>
>> I like the binding, but it is causing significant complexity in here.
> 
> Yes, in this patch it looks pretty bad. But with the suggested
> changes it at least looks fine (apart from the remaining ifdef
> in mux_control_get). But then there's of course the conceptual
> badness of the core depending on a specific driver that you
> mention...
> 
> But. I expect that gpio based muxes will be in vast majority, and
> giving them some extra freedoms is probably not wrong considering
> the upside of the simpler binding.
> 
Difficult balance. As you are going to be the poor soul who has
to maintain this I'm not that bothered either way ;)
Probably worth gathering a few more opinions on this though if
they are forthcoming.

Jonathan
>>>
>>> Cheers,
>>> Peter
>>>
>>>> -struct mux_gpio {
>>>> -	struct gpio_descs *gpios;
>>>> -	int *val;
>>>> -};
>>>> -
>>>> -static int mux_gpio_set(struct mux_control *mux, int state)
>>>> -{
>>>> -	struct mux_gpio *mux_gpio = mux_chip_priv(mux->chip);
>>>> -	int i;
>>>> -
>>>> -	for (i = 0; i < mux_gpio->gpios->ndescs; i++)
>>>> -		mux_gpio->val[i] = (state >> i) & 1;
>>>> -
>>>> -	gpiod_set_array_value_cansleep(mux_gpio->gpios->ndescs,
>>>> -				       mux_gpio->gpios->desc,
>>>> -				       mux_gpio->val);
>>>> -
>>>> -	return 0;
>>>> -}
>>>> -
>>>> -static const struct mux_control_ops mux_gpio_ops = {
>>>> -	.set = mux_gpio_set,
>>>> -};
>>>> -
>>>>  static const struct of_device_id mux_gpio_dt_ids[] = {
>>>>  	{ .compatible = "mux-gpio", },
>>>>  	{ /* sentinel */ }
>>>> @@ -51,38 +26,13 @@ MODULE_DEVICE_TABLE(of, mux_gpio_dt_ids);
>>>>  static int mux_gpio_probe(struct platform_device *pdev)
>>>>  {
>>>>  	struct device *dev = &pdev->dev;
>>>> -	struct device_node *np = dev->of_node;
>>>>  	struct mux_chip *mux_chip;
>>>> -	struct mux_gpio *mux_gpio;
>>>> -	int pins;
>>>>  	u32 idle_state;
>>>>  	int ret;
>>>>  
>>>> -	if (!np)
>>>> -		return -ENODEV;
>>>> -
>>>> -	pins = gpiod_count(dev, "mux");
>>>> -	if (pins < 0)
>>>> -		return pins;
>>>> -
>>>> -	mux_chip = devm_mux_chip_alloc(dev, 1, sizeof(*mux_gpio) +
>>>> -				       pins * sizeof(*mux_gpio->val));
>>>> -	if (!mux_chip)
>>>> -		return -ENOMEM;
>>>> -
>>>> -	mux_gpio = mux_chip_priv(mux_chip);
>>>> -	mux_gpio->val = (int *)(mux_gpio + 1);
>>>> -	mux_chip->ops = &mux_gpio_ops;
>>>> -
>>>> -	mux_gpio->gpios = devm_gpiod_get_array(dev, "mux", GPIOD_OUT_LOW);
>>>> -	if (IS_ERR(mux_gpio->gpios)) {
>>>> -		ret = PTR_ERR(mux_gpio->gpios);
>>>> -		if (ret != -EPROBE_DEFER)
>>>> -			dev_err(dev, "failed to get gpios\n");
>>>> -		return ret;
>>>> -	}
>>>> -	WARN_ON(pins != mux_gpio->gpios->ndescs);
>>>> -	mux_chip->mux->states = 1 << pins;
>>>> +	mux_chip = mux_gpio_alloc(dev);
>>>> +	if (IS_ERR(mux_chip))
>>>> +		return PTR_ERR(mux_chip);
>>>>  
>>>>  	ret = device_property_read_u32(dev, "idle-state", &idle_state);
>>>>  	if (ret >= 0) {
>>>> diff --git a/include/linux/mux.h b/include/linux/mux.h
>>>> index 3b9439927f11..3bfee23cfb8c 100644
>>>> --- a/include/linux/mux.h
>>>> +++ b/include/linux/mux.h
>>>> @@ -241,4 +241,11 @@ struct mux_control *devm_mux_control_get(struct device *dev,
>>>>   */
>>>>  void devm_mux_control_put(struct device *dev, struct mux_control *mux);
>>>>  
>>>> +struct mux_gpio {
>>>> +	struct gpio_descs *gpios;
>>>> +	int *val;
>>>> +};
>>>> +
>>>> +struct mux_chip *mux_gpio_alloc(struct device *dev);
>>>> +
>>>>  #endif /* _LINUX_MUX_H */
>>>>
>>>
>>
>