[PATCH v2] gpio: pca953x: remove incorrect le16_to_cpu calls

[PATCH v2] gpio: pca953x: remove incorrect le16_to_cpu calls

[Andy Shevchenko]

i2c_smbus commands handle the correct byte order for smbus transactions
internally. This will currently result in incorrect operation on big
endian systems.

Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
- add RB tag
 drivers/gpio/gpio-pca953x.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index 4c9e21300a26..1b9dbf691ae7 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -187,10 +187,9 @@ static int pca953x_write_regs_8(struct pca953x_chip *chip, int reg, u8 *val)
 
 static int pca953x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
 {
-	__le16 word = cpu_to_le16(get_unaligned((u16 *)val));
+	u16 word = get_unaligned((u16 *)val);
 
-	return i2c_smbus_write_word_data(chip->client,
-					 reg << 1, (__force u16)word);
+	return i2c_smbus_write_word_data(chip->client, reg << 1, word);
 }
 
 static int pca957x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
@@ -241,8 +240,7 @@ static int pca953x_read_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
 	int ret;
 
 	ret = i2c_smbus_read_word_data(chip->client, reg << 1);
-	val[0] = (u16)ret & 0xFF;
-	val[1] = (u16)ret >> 8;
+	put_unaligned(ret, (u16 *)val);
 
 	return ret;
 }
-- 
2.11.0

Re: [PATCH v2] gpio: pca953x: remove incorrect le16_to_cpu calls

[Gregory CLEMENT]

Hi Andy,
 
 On mar., juil. 18 2017, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> i2c_smbus commands handle the correct byte order for smbus
> transactions

I am not sure of this claim, I didn't find any cpu_to_lexx in the sbmus
function.

> internally. This will currently result in incorrect operation on big
> endian systems.

Did you managed to test this driver in a big endian system and to check
that with this patch the driver worked as expected?

Thanks,

Gregory


>
> Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> - add RB tag
>  drivers/gpio/gpio-pca953x.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
> index 4c9e21300a26..1b9dbf691ae7 100644
> --- a/drivers/gpio/gpio-pca953x.c
> +++ b/drivers/gpio/gpio-pca953x.c
> @@ -187,10 +187,9 @@ static int pca953x_write_regs_8(struct pca953x_chip *chip, int reg, u8 *val)
>  
>  static int pca953x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>  {
> -	__le16 word = cpu_to_le16(get_unaligned((u16 *)val));
> +	u16 word = get_unaligned((u16 *)val);
>  
> -	return i2c_smbus_write_word_data(chip->client,
> -					 reg << 1, (__force u16)word);
> +	return i2c_smbus_write_word_data(chip->client, reg << 1, word);
>  }
>  
>  static int pca957x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
> @@ -241,8 +240,7 @@ static int pca953x_read_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>  	int ret;
>  
>  	ret = i2c_smbus_read_word_data(chip->client, reg << 1);
> -	val[0] = (u16)ret & 0xFF;
> -	val[1] = (u16)ret >> 8;
> +	put_unaligned(ret, (u16 *)val);
>  
>  	return ret;
>  }
> -- 
> 2.11.0
>

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Re: [PATCH v2] gpio: pca953x: remove incorrect le16_to_cpu calls

[Andy Shevchenko]

On Wed, 2017-07-19 at 13:56 +0200, Gregory CLEMENT wrote:
> Hi Andy,
>  
>  On mar., juil. 18 2017, Andy Shevchenko <andriy.shevchenko@linux.inte
> l.com> wrote:
> 
> > i2c_smbus commands handle the correct byte order for smbus
> > transactions
> 
> I am not sure of this claim, I didn't find any cpu_to_lexx in the
> sbmus
> function.

Of course you didn't (I didn't either on the first glance, then I read
the code more carefully).

It does that byte-by-byte.

That explains why people do not notice it AFAIU Sebastian's claim.

> 
> > internally. This will currently result in incorrect operation on big
> > endian systems.
> 
> Did you managed to test this driver in a big endian system and to
> check
> that with this patch the driver worked as expected?

Unfortunately no. I have big endian systems, though I have no such
device connected to them.

> 
> Thanks,
> 
> Gregory
> 
> 
> > 
> > Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
> > Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > ---
> > - add RB tag
> >  drivers/gpio/gpio-pca953x.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-
> > pca953x.c
> > index 4c9e21300a26..1b9dbf691ae7 100644
> > --- a/drivers/gpio/gpio-pca953x.c
> > +++ b/drivers/gpio/gpio-pca953x.c
> > @@ -187,10 +187,9 @@ static int pca953x_write_regs_8(struct
> > pca953x_chip *chip, int reg, u8 *val)
> >  
> >  static int pca953x_write_regs_16(struct pca953x_chip *chip, int
> > reg, u8 *val)
> >  {
> > -	__le16 word = cpu_to_le16(get_unaligned((u16 *)val));
> > +	u16 word = get_unaligned((u16 *)val);
> >  
> > -	return i2c_smbus_write_word_data(chip->client,
> > -					 reg << 1, (__force
> > u16)word);
> > +	return i2c_smbus_write_word_data(chip->client, reg << 1,
> > word);
> >  }
> >  
> >  static int pca957x_write_regs_16(struct pca953x_chip *chip, int
> > reg, u8 *val)
> > @@ -241,8 +240,7 @@ static int pca953x_read_regs_16(struct
> > pca953x_chip *chip, int reg, u8 *val)
> >  	int ret;
> >  
> >  	ret = i2c_smbus_read_word_data(chip->client, reg << 1);
> > -	val[0] = (u16)ret & 0xFF;
> > -	val[1] = (u16)ret >> 8;
> > +	put_unaligned(ret, (u16 *)val);
> >  
> >  	return ret;
> >  }
> > -- 
> > 2.11.0
> > 
> 
> 

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

Re: [PATCH v2] gpio: pca953x: remove incorrect le16_to_cpu calls

[Phil Reid]

G'day Gregory,

On 19/07/2017 19:56, Gregory CLEMENT wrote:
> Hi Andy,
>   
>   On mar., juil. 18 2017, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> 
>> i2c_smbus commands handle the correct byte order for smbus
>> transactions
> 
> I am not sure of this claim, I didn't find any cpu_to_lexx in the sbmus
> function.
For example see: i2c_smbus_xfer_emulated
The I2C_SMBUS_WORD_DATA case. byte copies are done to do the cpu to le conversion.
      msgbuf0[1] = data->word & 0xff;
      msgbuf0[2] = data->word >> 8;

The patch looks good to me.

Reviewed-by: Phil Reid <preid@electromag.com.au>
> 
>> internally. This will currently result in incorrect operation on big
>> endian systems.
> 
> Did you managed to test this driver in a big endian system and to check
> that with this patch the driver worked as expected?
> 
> Thanks,
> 
> Gregory
> 
> 
>>
>> Suggested-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
>> Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> ---
>> - add RB tag
>>   drivers/gpio/gpio-pca953x.c | 8 +++-----
>>   1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
>> index 4c9e21300a26..1b9dbf691ae7 100644
>> --- a/drivers/gpio/gpio-pca953x.c
>> +++ b/drivers/gpio/gpio-pca953x.c
>> @@ -187,10 +187,9 @@ static int pca953x_write_regs_8(struct pca953x_chip *chip, int reg, u8 *val)
>>   
>>   static int pca953x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>>   {
>> -	__le16 word = cpu_to_le16(get_unaligned((u16 *)val));
>> +	u16 word = get_unaligned((u16 *)val);
>>   
>> -	return i2c_smbus_write_word_data(chip->client,
>> -					 reg << 1, (__force u16)word);
>> +	return i2c_smbus_write_word_data(chip->client, reg << 1, word);
>>   }
>>   
>>   static int pca957x_write_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>> @@ -241,8 +240,7 @@ static int pca953x_read_regs_16(struct pca953x_chip *chip, int reg, u8 *val)
>>   	int ret;
>>   
>>   	ret = i2c_smbus_read_word_data(chip->client, reg << 1);
>> -	val[0] = (u16)ret & 0xFF;
>> -	val[1] = (u16)ret >> 8;
>> +	put_unaligned(ret, (u16 *)val);
>>   
>>   	return ret;
>>   }
>> -- 
>> 2.11.0
>>
> 


-- 
Regards
Phil Reid

ElectroMagnetic Imaging Technology Pty Ltd
Development of Geophysical Instrumentation & Software
www.electromag.com.au

3 The Avenue, Midland WA 6056, AUSTRALIA
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