linux-kernel - Re: [PATCH] usb: typec: fsa4480: Check if the chip is really there

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Date: Tue, 13 Feb 2024 10:45:59 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Marijn Suijten <marijn.suijten@...ainline.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: typec: fsa4480: Check if the chip is really there

On Mon, Feb 12, 2024 at 01:59:42PM +0100, Konrad Dybcio wrote:
> On 12.02.2024 13:48, Greg Kroah-Hartman wrote:
> > On Mon, Feb 12, 2024 at 01:01:30PM +0100, Konrad Dybcio wrote:
> >> Currently, the driver will happily register the switch/mux devices, and
> >> so long as the i2c master doesn't complain, the user would never know
> >> there's something wrong.
> >>
> >> Add a device id check (based on [1]) and return -ENODEV if the read
> >> fails or returns nonsense.
> >>
> >> Checking the value on a Qualcomm SM6115P-based Lenovo Tab P11 tablet,
> >> the ID mentioned in the datasheet does indeed show up:
> >>  fsa4480 1-0042: Found FSA4480 v1.1 (Vendor ID = 0)
> >>
> >> [1] https://www.onsemi.com/pdf/datasheet/fsa4480-d.pdf
> >>
> >> Fixes: 1dc246320c6b ("usb: typec: mux: Add On Semi fsa4480 driver")
> >> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> >> ---
> >>  drivers/usb/typec/mux/fsa4480.c | 14 ++++++++++++++
> >>  1 file changed, 14 insertions(+)
> >>
> >> diff --git a/drivers/usb/typec/mux/fsa4480.c b/drivers/usb/typec/mux/fsa4480.c
> >> index cb7cdf90cb0a..d622f4f3bd54 100644
> >> --- a/drivers/usb/typec/mux/fsa4480.c
> >> +++ b/drivers/usb/typec/mux/fsa4480.c
> >> @@ -13,6 +13,10 @@
> >>  #include <linux/usb/typec_dp.h>
> >>  #include <linux/usb/typec_mux.h>
> >>  
> >> +#define FSA4480_DEVICE_ID	0x00
> >> + #define DEVICE_ID_VENDOR_ID	GENMASK(7, 6)
> >> + #define DEVICE_ID_VERSION_ID	GENMASK(5, 3)
> >> + #define DEVICE_ID_REV_ID	GENMASK(2, 0)
> > 
> > Why the indent?
> 
> In many places across the kernel, bitfields or possible values of a
> register are defined with an indentation to emphasize the relation between
> the defines

Ah, that wasn't obvious here because:

> > And those are _VERY_ generic #defines, please give a better name for
> > these so you don't conflict with other stuff in the kernel accidentally.
> 
> If you don't mind them becoming very long, I can prepend them with FSA4480_,
> and I suppose shrink 'VENDOR' to "VEN" and "VERSION" to "VER" to compensate

Yes, prepend them pleaase.  And no need to shorten the word, we have
plenty of space.

thanks,

greg k-h