linux-kernel - Re: [PATCH] gpio: pca953x: Use correct u16 value for register word write

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Message-ID: <CADO9-pdhTOmg9OMgz+K++Gc3mCxbi7KF23kA8zsftVeDTR3SSw@mail.gmail.com>
Date:	Tue, 29 Mar 2016 20:53:58 +0800
From:	Yong Li <sdliyong@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpio: pca953x: Use correct u16 value for register word write

Thanks for your comment, I think I can change it to val[0] | (val[1]
<< 8), is it okay ?

2016-03-29 20:06 GMT+08:00 Phil Reid <preid@...ctromag.com.au>:
> G'day Yong,
>
> One comment below.
>
> On 29/03/2016 2:27 PM, Yong Li wrote:
>>
>> The current implementation only uses the first byte in *val,
>> the second data is always 0. Change it to *(u16 *)val
>> to write the two bytes into the register
>>
>> Signed-off-by: Yong Li <sdliyong@...il.com>
>> ---
>>   drivers/gpio/gpio-pca953x.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
>> index d0d3065..cf3d410 100644
>> --- a/drivers/gpio/gpio-pca953x.c
>> +++ b/drivers/gpio/gpio-pca953x.c
>> @@ -159,7 +159,7 @@ static int pca953x_write_regs(struct pca953x_chip
>> *chip, int reg, u8 *val)
>>                 switch (chip->chip_type) {
>>                 case PCA953X_TYPE:
>>                         ret = i2c_smbus_write_word_data(chip->client,
>> -                                                       reg << 1, (u16)
>> *val);
>> +                                                       reg << 1, *(u16
>> *)val);
>
> I don't think this is safe for systems that don't support unaligned memory
> access.
>
>
>>                         break;
>>                 case PCA957X_TYPE:
>>                         ret = i2c_smbus_write_byte_data(chip->client, reg
>> << 1,
>>
>
>
> --
> Regards
> Phil Reid
>