On Sun, Oct 9, 2016 at 1:13 PM, Jonathan Cameron <jic23@xxxxxxxxxx> wrote: > On 05/10/16 19:00, sayli karnik wrote: >> On Wed, Oct 5, 2016 at 5:17 AM, Alison Schofield <amsfield22@xxxxxxxxx> wrote: >>> On Wed, Oct 05, 2016 at 03:17:22AM +0530, sayli karnik wrote: >>>> On Mon, Oct 3, 2016 at 10:46 PM, Alison Schofield <amsfield22@xxxxxxxxx> wrote: >>>>> On Mon, Oct 03, 2016 at 07:07:39PM +0530, sayli karnik wrote: >>>>>> On Mon, Oct 3, 2016 at 4:55 AM, Alison Schofield <amsfield22@xxxxxxxxx> wrote: >>>>>>> On Sun, Oct 02, 2016 at 05:53:08PM +0200, Lars-Peter Clausen wrote: >>>>>>>> On 10/02/2016 07:00 AM, Alison Schofield wrote: >>>>>>>> [...] >>>>>>>>>> --- >>>>>>>>>> drivers/iio/imu/bmi160/bmi160_core.c | 3 ++- >>>>>>>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>>>>>>> >>>>>>>>>> diff --git a/drivers/iio/imu/bmi160/bmi160_core.c b/drivers/iio/imu/bmi160/bmi160_core.c >>>>>>>>>> index e0251b8..5355507 100644 >>>>>>>>>> --- a/drivers/iio/imu/bmi160/bmi160_core.c >>>>>>>>>> +++ b/drivers/iio/imu/bmi160/bmi160_core.c >>>>>>>>>> @@ -398,7 +398,8 @@ static irqreturn_t bmi160_trigger_handler(int irq, void *p) >>>>>>>>>> struct iio_poll_func *pf = p; >>>>>>>>>> struct iio_dev *indio_dev = pf->indio_dev; >>>>>>>>>> struct bmi160_data *data = iio_priv(indio_dev); >>>>>>>>>> - s16 buf[16]; /* 3 sens x 3 axis x s16 + 3 x s16 pad + 4 x s16 tstamp */ >>>>>>>>>> + __le16 buf[16]; >>>>>>>>>> + /* 3 sens x 3 axis x __le16 + 3 x __le16 pad + 4 x __le16 tstamp */ >>>>>>>>>> int i, ret, j = 0, base = BMI160_REG_DATA_MAGN_XOUT_L; >>>>>>>>>> __le16 sample; >>>>>>>>> >>>>>>>>> Wondering about this option below. Data was read into an __le16, so that >>>>>>>>> was good diligence on drivers part. Seems we can use le16_to_cpu() for the >>>>>>>>> conversion into the buf. >>>>>>>>> >>>>>>>>> --- a/drivers/iio/imu/bmi160/bmi160_core.c >>>>>>>>> +++ b/drivers/iio/imu/bmi160/bmi160_core.c >>>>>>>>> @@ -408,7 +408,7 @@ static irqreturn_t bmi160_trigger_handler(int irq, void *p) >>>>>>>>> &sample, sizeof(__le16)); >>>>>>>>> if (ret < 0) >>>>>>>>> goto done; >>>>>>>>> - buf[j++] = sample; >>>>>>>>> + buf[j++] = le16_to_cpu(sample); >>>>>>>>> } >>>>>>>> >>>>>>>> This conversion is usually skipped on purpose and delayed until it is >>>>>>>> actually needed by the user. The IIO channel is accordingly marked that it >>>>>>>> will produce LE data. >>>>>>> Thanks Lars. I knew that for buffers, overlooked it, now I'll know it >>>>>>> better! >>>>>>> >>>>>>> So, Sayli, you probably got this from the analysis of the last patch. >>>>>>> In buffered mode, we'll go ahead and return the data in it's 'native' >>>>>>> order. So, my suggestion to convert it here, is wrong. Ignore ;) >>>>>>> >>>>>> Oh I see! So should I resend the patch with an updated >>>>>> description?(cosmetic/bug fix) >>>>> >>>>> Yes. In the commit message, you can leave out the subdirs (imu: bmc160:) >>>>> so that you have more space for a descriptive message of the change. >>>> >>>> A quick question about this being a bug fix or not. This would have >>>> worked fine on little endian systems. But wouldn't the byte order have >>>> changed in case of a big endian buffer, when the little endian samples >>>> are stored in it? >>>> If not, then this will be a cosmetic patch. >>>> >>>> thanks, >>>> sayli >>> >>> Hi Sayli, >>> Pulling linux-iio back in. Once we've started group thread, we need to >>> keep replying to 'all'. It helps those invested in this particular >>> patch, and also helps those who search in the future with similar >>> issues. >>> >>> To answer your question. I say cosmetic, because the le16 is going >>> into a 16bit buf element, and is labelled as IIO_LE in the channel >>> buffer definition. That's why Lars was saying we don't need to do >>> any conversion. We'll pass the bits as they came in, and tell the >>> readers of the buf that they are in little endian format. (And, also >>> note we weren't truncating any as was the case in your first endian fix.) >>> >> Noted! >> >>> OK - having said that, I stare at this code more, and wonder why >>> we are even bothering to label the sample as __le16, and whether >>> we should just label it as s16. >> >> Oh, in that case we could make both buf and sample s16. > I actually fall just the other way. They are little endian so we > should mark them as such, whether or not we are going to do any > conversions on them in kernel. It acts as a form of documentation > and makes it a little more obvious what the code is doing. > It gets vaguer with buffer as that is a mixed endian beast. > If you really want that one right you could use a structure, but > honestly it's not worth the hassle. > >> >> Also, I'm wondering about the use >>> of sizeof(). Shouldn't we be saying sizeof(sample) not sizeof(__le16)? >>> It's not a checkpatch error, but I feel like I've seen coccichecks >>> or coccinelle script patches repairing these misuses of sizeof >>> >> Yes sizeof(variable) instead of sizeof(type) makes code resistant to >> future type changes. > Absolutely (I missed that in the original reviews!) > I have sent an updated patch, but forgot to mention the version. Does this comment make sense with __le16 instead of s16? /* 3 sens x 3 axis x __le16 + 3 x __le16 pad + 4 x __le16 tstamp */ thanks, sayli > Jonathan >> >>> See what you think, group reply with questions, and we'll get to the >>> bottom of this one soon! >>> >>> Thanks, >>> alisons >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-iio" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
