Re: [Gta04-owner] [PATCH 3/4] usb: phy: twl4030: add support for reading restore on ID pin.

Dr. H. Nikolaus Schaller
2015-03-04T06:55:05Z

Am 04.03.2015 um 07:35 schrieb NeilBrown <neilb@suse.de>:

> On Mon, 2 Mar 2015 22:04:31 +0100 Pavel Machek <pavel@ucw.cz> wrote:
>
>> Hi!
>>
>>> The twl4030 phy can measure, with low precision, the
>>> resistance-to-ground of the ID pin.
>>>
>>> Add a function to read the value, and export the result
>>> via sysfs.
>>>
>>> If the read fails, which it does sometimes, try again in 50msec.
>>>
>>> Signed-off-by: NeilBrown <neilb@suse.de>
>>> ---
>>> drivers/phy/phy-twl4030-usb.c | 63 +++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 63 insertions(+)
>>>
>>> diff --git a/drivers/phy/phy-twl4030-usb.c b/drivers/phy/phy-twl4030-usb.c
>>> index 023fe150c7a1..759950898df9 100644
>>> --- a/drivers/phy/phy-twl4030-usb.c
>>> +++ b/drivers/phy/phy-twl4030-usb.c
>>> @@ -374,6 +374,56 @@ static void twl4030_i2c_access(struct twl4030_usb *twl, int on)
>>> }
>>> }
>>>
>>> +enum twl4030_id_status {
>>> + TWL4030_GROUND,
>>> + TWL4030_102K,
>>> + TWL4030_200K,
>>> + TWL4030_440K,
>>> + TWL4030_FLOATING,
>>> + TWL4030_ID_UNKNOWN,
>>> +};
>>> +static char *twl4030_id_names[] = {
>>> + "ground",
>>> + "102k",
>>> + "200k",
>>> + "440k",
>>
>> New /sys files should be documented somewhere...?
>
> Preferably with the code...
>
>>
>> Does it make sense to change "440k" -> "440KOhm"?
>
> Interesting question. I prefer to avoid including units in files - bare
> numbers is better. But there is no number to match "floating" unless I spell
> it out as "infinity", and wouldn't be helpful.
>
> Certainly "K" would be preferred over "k“,

The international standard for kilo = 1000 is a lower case k.
While it is (non-standard) to use K for 1024:

http://en.wikipedia.org/wiki/Kilobyte

So I would keep the string constants lower case to avoid this potential confusion.

> and given that I have "ground"
> and "floating", it is more consistent to include the "Ohm"....
>
> These are really names, not measures of resistance. The data sheet calls
> them:
> ID_RES_FLOAT (or sometimes ID_FLOAT)
> ID_RES_440K
> ID_RES_200K
> ID_RES_102K
> ID_GND (or sometimes ID_RES_GND)
>
> So using those names is defensible.
>
> I think I'll change them all to upper case, but leave out the "Ohm".
> My justification is consistency with the data sheet.
>
>
>
>
>>
>> Plus I guess you need to update Documentation/
>
> I guess I'll need to give in to this eventually :-)
>
>>
>> Acked-by: Pavel Machek <pavel@ucw.cz>
>>
>
> Thanks,
> NeilBrown
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