Re: [PATCH 03/11] mux: consumer.h: Add MUX_USB_* state constant defines

Hans de Goede
2017-09-02T19:46:19Z

Hi,

On 02-09-17 21:06, Guenter Roeck wrote:
> On Sat, Sep 02, 2017 at 05:59:14PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 02-09-17 16:59, Guenter Roeck wrote:
>>> On 09/01/2017 02:48 PM, Hans de Goede wrote:
>>>> Add MUX_USB_* state constant defines, which can be used by USB
>>>> device/host and Type-C polarity/role/altmode mux drivers and consumers
>>>> to ensure that they agree on the meaning of the mux_control_select()
>>>> state argument.
>>>>
>>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>>> ---
>>>> include/linux/mux/consumer.h | 16 ++++++++++++++++
>>>> 1 file changed, 16 insertions(+)
>>>>
>>>> diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
>>>> index 912dd48a3a5d..e3ec9b4db962 100644
>>>> --- a/include/linux/mux/consumer.h
>>>> +++ b/include/linux/mux/consumer.h
>>>> @@ -15,6 +15,22 @@
>>>> #include <linux/compiler.h>
>>>> +/*
>>>> + * Mux state values for USB muxes, used for both USB device/host role muxes
>>>> + * as well as for Type-C polarity/role/altmode muxes.
>>>> + *
>>>> + * MUX_USB_POLARITY_INV may be or-ed together with any other mux-state as
>>>> + * inverted-polarity (Type-C plugged in upside down) can happen with any
>>>> + * other mux-state.
>>>> + */
>>>> +#define MUX_USB_POLARITY_INV BIT(0) /* Polarity inverted bit */
>>>> +#define MUX_USB_NONE (1 << 1) /* Mux open / not connected */
>>>
>>>
>>> Why BIT(0) but (1 << 1) and so on ?
>>
>> Because the polarity can be or-ed together with any of the other options.
>> Each option can be selected normal and inverted polarity (connector
>> inserted upside down).
>>
> Ah yes, it is (2 << 1), not (1 << 2).

Ack.

> But then why don't the options start > with (0 << 1) ?

Because I somehow thought that would conflict with the polarity
bit which of course it will not, so I will fix this for v2.

Note I used BIT(0) for the flag and not say BIT(8) because the mux subsys expects
a mux-driver to declare a max value for the state parameter to mux_control_select(),
which is what the MUX_USB_STATES define is for. If I were to use say BIT(8) for
the polarity then the MUX_USB_STATES value would become (256 + 5) even though we
only have 12 unique states.

> I'll have to look into the series more closely;

Thank you.

> so far the polarity was
> a separate parameter to tcpm_mux_set() and the low level API.

Right, I've kept the polarity as a separate parameter at the tcpm level,
but the mux_control_select() function has only one argument, so I or
the polarity and the alt-mode to mux for together there.

Regards,

Hans

>
> Guenter
>
>> Regards,
>>
>> Hans
>>
>>>> +#define MUX_USB_DEVICE (2 << 1) /* USB device mode */
>>>> +#define MUX_USB_HOST (3 << 1) /* USB host mode */
>>>> +#define MUX_USB_HOST_AND_DP_SRC (4 << 1) /* USB host + 2 lanes Display Port */
>>>> +#define MUX_USB_DP_SRC (5 << 1) /* 4 lanes Display Port source */
>>>> +#define MUX_USB_STATES (6 << 1)
>>>> +
>>>> struct device;
>>>> struct mux_control;
>>>>
>>>