Re: [PATCH 02/10] mfd: rt5033: Fix chip revision readout

[Jakob Hauser]

Hi Lee,

On 06.03.23 10:18, Lee Jones wrote:
> On Sun, 05 Mar 2023, Jakob Hauser wrote:
>
> > Hi Lee,
> >
> > On 05.03.23 11:47, Lee Jones wrote:
> > > On Tue, 28 Feb 2023, Jakob Hauser wrote:
> > >
> > > > After reading the data from the DEVICE_ID register, mask 0x0f needs to be
> > > > applied to extract the revision of the chip [1].
> > > >
> > > > The other part of the DEVICE_ID register, mask 0xf0, is a vendor identification
> > > > code. That's how it is set up at similar products of Richtek, e.g. RT9455 [2]
> > > > page 21 top.
> > > >
> > > > [1] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/mfd/rt5033_core.c#L484
> > > > [2] https://www.richtek.com/assets/product_file/RT9455/DS9455-00.pdf
> > > >
> > > > Signed-off-by: Jakob Hauser <jahau@xxxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/mfd/rt5033.c               | 8 +++++---
> > > >    include/linux/mfd/rt5033-private.h | 4 ++++
> > > >    2 files changed, 9 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/mfd/rt5033.c b/drivers/mfd/rt5033.c
> > > > index 8029d444b794..d32467174cb5 100644
> > > > --- a/drivers/mfd/rt5033.c
> > > > +++ b/drivers/mfd/rt5033.c
> > > > @@ -55,7 +55,8 @@ static const struct regmap_config rt5033_regmap_config = {
> > > >    static int rt5033_i2c_probe(struct i2c_client *i2c)
> > > >    {
> > > >    	struct rt5033_dev *rt5033;
> > > > -	unsigned int dev_id;
> > > > +	unsigned int data;
> > >
> > > In terms of nomenclature, this is a regression.
> > >
> > > 'data' is a terrible variable name.  Why not keep it as-is?
> >
> > While not having a datasheet for RT5033 available, in similar products like
> > RT9455 the register is called "Device ID", the first part of that is
> > "VENDOR_ID" and the second part "CHIP_REV", [1] page 23 top. Or in RT5036
> > preliminary data sheet the register is called "ID", the first part
> > "VENDOR_ID" and the second part "CHIP_REV_ID", [2] page 27 top.
> >
> > I wanted to avoid confusion between "dev_id" and "chip_rev". Therefore in
> > the patch it's written as getting some "data" from the register and extract
> > "chip_rev" from that data.
> >
> > I could change it to "reg_data"? Or something in that direction? I still
> > think that getting "chip_rev" out of "dev_id" would be confusing.
>
> You're reading from a register called RT5033_REG_DEVICE_ID.  I don't see
> any reason why the variable you read into can't reflect that.

OK, I'll use "dev_id" and "chip_rev" for the variable names.

...

Kind regards,
Jakob