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Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional

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  Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional Uwe Kleine-König   <u.kleine-koenig@pengutronix.de> - 2016-01-15 09:00 +0100
    Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional Li Yang <leoli@freescale.com> - 2016-01-15 09:50 +0100
      Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional Uwe Kleine-König   <u.kleine-koenig@pengutronix.de> - 2016-01-15 10:10 +0100
        Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional Li Yang <leoli@freescale.com> - 2016-01-18 09:30 +0100
          Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional Uwe Kleine-König   <u.kleine-koenig@pengutronix.de> - 2016-01-18 09:40 +0100

#1309931 — Re: [PATCH v3] i2c: imx: make bus recovery through pinctrl optional

Hello,

On Fri, Jan 15, 2016 at 01:27:24AM -0600, Li Yang wrote:
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index a2b132c..1239bfa 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -1081,8 +1081,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	/* optional bus recovery feature through pinctrl */
>  	i2c_imx->pinctrl = devm_pinctrl_get(&pdev->dev);
> -	if (IS_ERR(i2c_imx->pinctrl)) {
> +	/* bailout on -ENOMEM or -EPROBE_DEFER, continue for other errors */
> +	if (PTR_ERR(i2c_imx->pinctrl) == -ENOMEM ||
> +			PTR_ERR(i2c_imx->pinctrl) == -EPROBE_DEFER) {
>  		ret = PTR_ERR(i2c_imx->pinctrl);
>  		goto clk_disable;
>  	}
> @@ -1125,7 +1128,10 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  			i2c_imx, IMX_I2C_I2CR);
>  	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
>  
> -	i2c_imx_init_recovery_info(i2c_imx, pdev);
> +	if (IS_ERR_OR_NULL(i2c_imx->pinctrl))

I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use

	if (!i2c_imx->pinctrl)

here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
to keep the caller simple?)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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#1309960

On Fri, Jan 15, 2016 at 3:53 PM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> Hello,
>
> On Fri, Jan 15, 2016 at 01:27:24AM -0600, Li Yang wrote:
>> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
>> index a2b132c..1239bfa 100644
>> --- a/drivers/i2c/busses/i2c-imx.c
>> +++ b/drivers/i2c/busses/i2c-imx.c
>> @@ -1081,8 +1081,11 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>               return ret;
>>       }
>>
>> +     /* optional bus recovery feature through pinctrl */
>>       i2c_imx->pinctrl = devm_pinctrl_get(&pdev->dev);
>> -     if (IS_ERR(i2c_imx->pinctrl)) {
>> +     /* bailout on -ENOMEM or -EPROBE_DEFER, continue for other errors */
>> +     if (PTR_ERR(i2c_imx->pinctrl) == -ENOMEM ||
>> +                     PTR_ERR(i2c_imx->pinctrl) == -EPROBE_DEFER) {
>>               ret = PTR_ERR(i2c_imx->pinctrl);
>>               goto clk_disable;
>>       }
>> @@ -1125,7 +1128,10 @@ static int i2c_imx_probe(struct platform_device *pdev)
>>                       i2c_imx, IMX_I2C_I2CR);
>>       imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
>>
>> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
>> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
>
> I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use
>
>         if (!i2c_imx->pinctrl)
>
> here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
> to keep the caller simple?)

Setting not used pointer to NULL might be a good coding practice
generally.  But in this case neither the driver nor gpio framework
checks if the pinctrl is NULL before accessing it.  We still need the
driver to make sure pinctrl is not used in this situation.  The
benefit of the proposed change seems to be pretty limited.  :)

Regards,
Leo

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#1309972

Hello Li,

On Fri, Jan 15, 2016 at 04:46:06PM +0800, Li Yang wrote:
> On Fri, Jan 15, 2016 at 3:53 PM, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> >> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
> >> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
> >
> > I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use
> >
> >         if (!i2c_imx->pinctrl)
> >
> > here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
> > to keep the caller simple?)
> 
> Setting not used pointer to NULL might be a good coding practice
> generally.  But in this case neither the driver nor gpio framework
> checks if the pinctrl is NULL before accessing it.  We still need the
> driver to make sure pinctrl is not used in this situation.  The
> benefit of the proposed change seems to be pretty limited.  :)

At least it gets rid of IS_ERR_OR_NULL which is used wrongly more often
than not.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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#1311368

On Fri, Jan 15, 2016 at 5:03 PM, Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
> Hello Li,
>
> On Fri, Jan 15, 2016 at 04:46:06PM +0800, Li Yang wrote:
>> On Fri, Jan 15, 2016 at 3:53 PM, Uwe Kleine-König
>> <u.kleine-koenig@pengutronix.de> wrote:
>> >> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
>> >> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
>> >
>> > I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use
>> >
>> >         if (!i2c_imx->pinctrl)
>> >
>> > here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
>> > to keep the caller simple?)
>>
>> Setting not used pointer to NULL might be a good coding practice
>> generally.  But in this case neither the driver nor gpio framework
>> checks if the pinctrl is NULL before accessing it.  We still need the
>> driver to make sure pinctrl is not used in this situation.  The
>> benefit of the proposed change seems to be pretty limited.  :)
>
> At least it gets rid of IS_ERR_OR_NULL which is used wrongly more often
> than not.

It's true that this API is not used a lot.  Are you suggesting that it
is poorly designed and probably should be removed?  But I still don't
quite get the point why it tends to be wrongly used.  Do you consider
the use in this patch a wrongly used case?

Regards,
Leo

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#1311377

Hello Leo,

On Mon, Jan 18, 2016 at 04:22:51PM +0800, Li Yang wrote:
> On Fri, Jan 15, 2016 at 5:03 PM, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > On Fri, Jan 15, 2016 at 04:46:06PM +0800, Li Yang wrote:
> >> On Fri, Jan 15, 2016 at 3:53 PM, Uwe Kleine-König
> >> <u.kleine-koenig@pengutronix.de> wrote:
> >> >> -     i2c_imx_init_recovery_info(i2c_imx, pdev);
> >> >> +     if (IS_ERR_OR_NULL(i2c_imx->pinctrl))
> >> >
> >> > I'd prefer to set i2c_imx->pinctrl to NULL if it's not used and then use
> >> >
> >> >         if (!i2c_imx->pinctrl)
> >> >
> >> > here. (Or maybe make i2c_imx_init_recovery_info aware of this situation
> >> > to keep the caller simple?)
> >>
> >> Setting not used pointer to NULL might be a good coding practice
> >> generally.  But in this case neither the driver nor gpio framework
> >> checks if the pinctrl is NULL before accessing it.  We still need the
> >> driver to make sure pinctrl is not used in this situation.  The
> >> benefit of the proposed change seems to be pretty limited.  :)
> >
> > At least it gets rid of IS_ERR_OR_NULL which is used wrongly more often
> > than not.
> 
> It's true that this API is not used a lot.  Are you suggesting that it
> is poorly designed and probably should be removed?  But I still don't
> quite get the point why it tends to be wrongly used.  Do you consider
> the use in this patch a wrongly used case?

See http://permalink.gmane.org/gmane.linux.ports.arm.omap/97874 for an
earlier discussion. Having said that, I think at the moment there is no
such bug in this case, still I agree with Russell that IS_ERR_OR_NULL
isn't nice and so would prefer not to add new instances.

Best regards
Uwe


-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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