diff mbox series

[3/5] i2c-mux-gpio: Save initial channel number to the idle data field

Message ID 20190424123414.25311-4-fancer.lancer@gmail.com
State Superseded
Headers show
Series i2c-mux-gpio: Split plat- and dt-specific code up | expand

Commit Message

Serge Semin April 24, 2019, 12:34 p.m. UTC
In case if the idle state has been specified in the data structure,
the idle variable is left untouched as before, so to keep a default
channel number enabled in the mux idle state. But if a platform doesn't
specify which channel is going to be enabled by default, we as before
don't setup the deselect callback, but the initial state is saved in the
idle variable for further initialization. We can safely do this here
since that variable is used for initial state setting only, when no
idling lane is specified.

The reason of this change is to prepare the code for future GPIOs request
path being split up into of- and plat- based methods. The idle variable
here is used as a container of the initial state for both of the paths in
case of idle-channel isn't specified.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
---
 drivers/i2c/muxes/i2c-mux-gpio.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

Comments

Peter Rosin April 24, 2019, 9:26 p.m. UTC | #1
On 2019-04-24 14:34, Serge Semin wrote:
> In case if the idle state has been specified in the data structure,
> the idle variable is left untouched as before, so to keep a default
> channel number enabled in the mux idle state. But if a platform doesn't
> specify which channel is going to be enabled by default, we as before
> don't setup the deselect callback, but the initial state is saved in the
> idle variable for further initialization. We can safely do this here
> since that variable is used for initial state setting only, when no
> idling lane is specified.

While this subtlety is *maybe* ok, a comment about it belongs in the
*code* where it will be seen when the next person makes changes.

But why not extend the struct with the initial state? How many of
these muxes do you expect to exist in a system? Multiplied by a
couple of bytes. Who cares?

Cheers,
Peter

> 
> The reason of this change is to prepare the code for future GPIOs request
> path being split up into of- and plat- based methods. The idle variable
> here is used as a container of the initial state for both of the paths in
> case of idle-channel isn't specified.
> 
> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> ---
>  drivers/i2c/muxes/i2c-mux-gpio.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
> index a14fe132b0c3..535c83c43371 100644
> --- a/drivers/i2c/muxes/i2c-mux-gpio.c
> +++ b/drivers/i2c/muxes/i2c-mux-gpio.c
> @@ -171,7 +171,6 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>  	struct gpiomux *mux;
>  	struct i2c_adapter *parent;
>  	struct i2c_adapter *root;
> -	unsigned initial_state;
>  	int i, ret;
>  
>  	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
> @@ -204,12 +203,14 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>  
>  	muxc->mux_locked = true;
>  
> -	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE) {
> -		initial_state = mux->data.idle;
> +	/*
> +	 * Set descelect callback if idle state has been setup otherwise just
> +	 * use the idle variable to store the initial muxer value.
> +	 */
> +	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE)
>  		muxc->deselect = i2c_mux_gpio_deselect;
> -	} else {
> -		initial_state = mux->data.values[0];
> -	}
> +	else
> +		mux->data.idle = mux->data.values[0];
>  
>  	for (i = 0; i < mux->data.n_gpios; i++) {
>  		struct device *gpio_dev;
> @@ -224,7 +225,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>  		}
>  
>  		ret = gpio_direction_output(mux->gpio_base + mux->data.gpios[i],
> -					    initial_state & (1 << i));
> +					    mux->data.idle & (1 << i));
>  		if (ret) {
>  			dev_err(&pdev->dev,
>  				"Failed to set direction of GPIO %d to output\n",
>
Serge Semin April 25, 2019, 3:53 p.m. UTC | #2
On Wed, Apr 24, 2019 at 09:26:22PM +0000, Peter Rosin wrote:
> On 2019-04-24 14:34, Serge Semin wrote:
> > In case if the idle state has been specified in the data structure,
> > the idle variable is left untouched as before, so to keep a default
> > channel number enabled in the mux idle state. But if a platform doesn't
> > specify which channel is going to be enabled by default, we as before
> > don't setup the deselect callback, but the initial state is saved in the
> > idle variable for further initialization. We can safely do this here
> > since that variable is used for initial state setting only, when no
> > idling lane is specified.
> 
> While this subtlety is *maybe* ok, a comment about it belongs in the
> *code* where it will be seen when the next person makes changes.
> 
> But why not extend the struct with the initial state? How many of
> these muxes do you expect to exist in a system? Multiplied by a
> couple of bytes. Who cares?
> 

I actually thought about this when started working on the patchset.
That time saving the initial value in the idle variable seemed like a
good idea. I even put a small comment in the code about this.

Anyway lets add a new field to "struct gpiomux" structure and use
it as a container for initial value. It is also a good alternative.
I'll do this in a v2 patchset.

-Sergey

> Cheers,
> Peter
> 
> > 
> > The reason of this change is to prepare the code for future GPIOs request
> > path being split up into of- and plat- based methods. The idle variable
> > here is used as a container of the initial state for both of the paths in
> > case of idle-channel isn't specified.
> > 
> > Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
> > ---
> >  drivers/i2c/muxes/i2c-mux-gpio.c | 15 ++++++++-------
> >  1 file changed, 8 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
> > index a14fe132b0c3..535c83c43371 100644
> > --- a/drivers/i2c/muxes/i2c-mux-gpio.c
> > +++ b/drivers/i2c/muxes/i2c-mux-gpio.c
> > @@ -171,7 +171,6 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
> >  	struct gpiomux *mux;
> >  	struct i2c_adapter *parent;
> >  	struct i2c_adapter *root;
> > -	unsigned initial_state;
> >  	int i, ret;
> >  
> >  	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
> > @@ -204,12 +203,14 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
> >  
> >  	muxc->mux_locked = true;
> >  
> > -	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE) {
> > -		initial_state = mux->data.idle;
> > +	/*
> > +	 * Set descelect callback if idle state has been setup otherwise just
> > +	 * use the idle variable to store the initial muxer value.
> > +	 */
> > +	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE)
> >  		muxc->deselect = i2c_mux_gpio_deselect;
> > -	} else {
> > -		initial_state = mux->data.values[0];
> > -	}
> > +	else
> > +		mux->data.idle = mux->data.values[0];
> >  
> >  	for (i = 0; i < mux->data.n_gpios; i++) {
> >  		struct device *gpio_dev;
> > @@ -224,7 +225,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
> >  		}
> >  
> >  		ret = gpio_direction_output(mux->gpio_base + mux->data.gpios[i],
> > -					    initial_state & (1 << i));
> > +					    mux->data.idle & (1 << i));
> >  		if (ret) {
> >  			dev_err(&pdev->dev,
> >  				"Failed to set direction of GPIO %d to output\n",
> > 
>
Peter Rosin April 25, 2019, 7:32 p.m. UTC | #3
On 2019-04-25 17:53, Serge Semin wrote:
> On Wed, Apr 24, 2019 at 09:26:22PM +0000, Peter Rosin wrote:
>> On 2019-04-24 14:34, Serge Semin wrote:
>>> In case if the idle state has been specified in the data structure,
>>> the idle variable is left untouched as before, so to keep a default
>>> channel number enabled in the mux idle state. But if a platform doesn't
>>> specify which channel is going to be enabled by default, we as before
>>> don't setup the deselect callback, but the initial state is saved in the
>>> idle variable for further initialization. We can safely do this here
>>> since that variable is used for initial state setting only, when no
>>> idling lane is specified.
>>
>> While this subtlety is *maybe* ok, a comment about it belongs in the
>> *code* where it will be seen when the next person makes changes.
>>
>> But why not extend the struct with the initial state? How many of
>> these muxes do you expect to exist in a system? Multiplied by a
>> couple of bytes. Who cares?
>>
> 
> I actually thought about this when started working on the patchset.
> That time saving the initial value in the idle variable seemed like a
> good idea. I even put a small comment in the code about this.

Oh, I missed that. Crap, and sorry!

> Anyway lets add a new field to "struct gpiomux" structure and use
> it as a container for initial value. It is also a good alternative.
> I'll do this in a v2 patchset.

Good. Thanks!

Cheers,
Peter

> -Sergey
> 
>> Cheers,
>> Peter
>>
>>>
>>> The reason of this change is to prepare the code for future GPIOs request
>>> path being split up into of- and plat- based methods. The idle variable
>>> here is used as a container of the initial state for both of the paths in
>>> case of idle-channel isn't specified.
>>>
>>> Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
>>> ---
>>>  drivers/i2c/muxes/i2c-mux-gpio.c | 15 ++++++++-------
>>>  1 file changed, 8 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
>>> index a14fe132b0c3..535c83c43371 100644
>>> --- a/drivers/i2c/muxes/i2c-mux-gpio.c
>>> +++ b/drivers/i2c/muxes/i2c-mux-gpio.c
>>> @@ -171,7 +171,6 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>>>  	struct gpiomux *mux;
>>>  	struct i2c_adapter *parent;
>>>  	struct i2c_adapter *root;
>>> -	unsigned initial_state;
>>>  	int i, ret;
>>>  
>>>  	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
>>> @@ -204,12 +203,14 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>>>  
>>>  	muxc->mux_locked = true;
>>>  
>>> -	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE) {
>>> -		initial_state = mux->data.idle;
>>> +	/*
>>> +	 * Set descelect callback if idle state has been setup otherwise just

Spelling "deselect"

>>> +	 * use the idle variable to store the initial muxer value.
>>> +	 */
>>> +	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE)
>>>  		muxc->deselect = i2c_mux_gpio_deselect;
>>> -	} else {
>>> -		initial_state = mux->data.values[0];
>>> -	}
>>> +	else
>>> +		mux->data.idle = mux->data.values[0];
>>>  
>>>  	for (i = 0; i < mux->data.n_gpios; i++) {
>>>  		struct device *gpio_dev;
>>> @@ -224,7 +225,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
>>>  		}
>>>  
>>>  		ret = gpio_direction_output(mux->gpio_base + mux->data.gpios[i],
>>> -					    initial_state & (1 << i));
>>> +					    mux->data.idle & (1 << i));
>>>  		if (ret) {
>>>  			dev_err(&pdev->dev,
>>>  				"Failed to set direction of GPIO %d to output\n",
>>>
>>
diff mbox series

Patch

diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c
index a14fe132b0c3..535c83c43371 100644
--- a/drivers/i2c/muxes/i2c-mux-gpio.c
+++ b/drivers/i2c/muxes/i2c-mux-gpio.c
@@ -171,7 +171,6 @@  static int i2c_mux_gpio_probe(struct platform_device *pdev)
 	struct gpiomux *mux;
 	struct i2c_adapter *parent;
 	struct i2c_adapter *root;
-	unsigned initial_state;
 	int i, ret;
 
 	mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
@@ -204,12 +203,14 @@  static int i2c_mux_gpio_probe(struct platform_device *pdev)
 
 	muxc->mux_locked = true;
 
-	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE) {
-		initial_state = mux->data.idle;
+	/*
+	 * Set descelect callback if idle state has been setup otherwise just
+	 * use the idle variable to store the initial muxer value.
+	 */
+	if (mux->data.idle != I2C_MUX_GPIO_NO_IDLE)
 		muxc->deselect = i2c_mux_gpio_deselect;
-	} else {
-		initial_state = mux->data.values[0];
-	}
+	else
+		mux->data.idle = mux->data.values[0];
 
 	for (i = 0; i < mux->data.n_gpios; i++) {
 		struct device *gpio_dev;
@@ -224,7 +225,7 @@  static int i2c_mux_gpio_probe(struct platform_device *pdev)
 		}
 
 		ret = gpio_direction_output(mux->gpio_base + mux->data.gpios[i],
-					    initial_state & (1 << i));
+					    mux->data.idle & (1 << i));
 		if (ret) {
 			dev_err(&pdev->dev,
 				"Failed to set direction of GPIO %d to output\n",