Messages in this thread | | | Subject | Re: [PATCH -next v2] staging: comedi: Remove un used variable ‘min full scale’ and function 'get min full scales' | From | Ian Abbott <> | Date | Fri, 14 May 2021 12:16:11 +0100 |
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On 14/05/2021 08:52, Greg KH wrote: > On Fri, May 14, 2021 at 04:52:14PM +0800, Bixuan Cui wrote: >> The variable ‘min_full_scale’ and function 'get_min_full_scales' are >> not used, So delete them. >> >> Signed-off-by: Bixuan Cui <cuibixuan@huawei.com> >> --- >> Changes from v2: >> * Delete function 'get_min_full_scales' >> >> drivers/comedi/drivers/jr3_pci.c | 15 --------------- >> 1 file changed, 15 deletions(-) >> >> diff --git a/drivers/comedi/drivers/jr3_pci.c b/drivers/comedi/drivers/jr3_pci.c >> index 7a02c4fa3cda..f963080dd61f 100644 >> --- a/drivers/comedi/drivers/jr3_pci.c >> +++ b/drivers/comedi/drivers/jr3_pci.c >> @@ -186,19 +186,6 @@ static void set_full_scales(struct jr3_sensor __iomem *sensor, >> set_s16(&sensor->command_word0, 0x0a00); >> } >> >> -static struct six_axis_t get_min_full_scales(struct jr3_sensor __iomem *sensor) >> -{ >> - struct six_axis_t result; >> - >> - result.fx = get_s16(&sensor->min_full_scale.fx); >> - result.fy = get_s16(&sensor->min_full_scale.fy); >> - result.fz = get_s16(&sensor->min_full_scale.fz); >> - result.mx = get_s16(&sensor->min_full_scale.mx); >> - result.my = get_s16(&sensor->min_full_scale.my); >> - result.mz = get_s16(&sensor->min_full_scale.mz); >> - return result; > > Are you _SURE_ that this is ok to do? You are reading from the > hardware, and that is sometimes required depending on the > internal-to-the-device state machine. > > Have you tested to verify that not doing these reads does not break > something? > > This is a constant theme in these "remove variables that are not being > used" patches, please be aware that how hardware works is very specific > and when you mess with how it is accessed, that has the chance of > causing problems.
I don't think removing this would do any harm. The `get_s16` function is just a simple wrapper around `readl` that converts the type of the returned value to `s16`. The registers for minimum full scale and maximum full scale are just informational, and there is nothing in the manual[1] about reading registers in a particular order. The driver used to print these values to the kernel log, but that code was removed in commit a1d16659538a ("staging: comedi: jr3_pci: remove noisy printk").
[1] 5907E - Legacy PCI Receiver Manual <https://www.jr3.com/component/phocadownload/category/6-product-manuals?download=36:5907e-legacy-pci-receiver-manual>
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