linux-kernel - Re: [PATCH 03/11] mux: consumer.h: Add MUX_USB

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Date:   Sat, 2 Sep 2017 13:59:53 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Peter Rosin <peda@...ntia.se>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        devel@...verdev.osuosl.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Sathyanarayanan Kuppuswamy Natarajan <sathyaosid@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        USB <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 03/11] mux: consumer.h: Add MUX_USB_* state constant
 defines

Hi,

On 02-09-17 12:10, Andy Shevchenko wrote:
> On Sat, Sep 2, 2017 at 12:48 AM, Hans de Goede <hdegoede@...hat.com> 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.
> 
>> +/*
>> + * 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 */
>> +#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)
> 
> I would put OR'ed bits higher.
> 
> Like allocate 4 (8) bits for states and start special flags from bit
> 8 and so on.

That is not an option because the mux framework expects a mux to declare
how much states it has (which is where the MUX_USB_STATES define comes in)
and any attemp to set a state higher then max_states will return with
-EINVAL.

Regards,

Hans