linux-kernel - Re: [PATCH v4 4/4] dt-bindings: net: broadcom-bluetooth: Add pcm config

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Date:   Thu, 14 Nov 2019 11:20:14 -0800
From:   Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        linux-bluetooth@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ondrej Jirman <megous@...ous.com>,
        Mark Rutland <mark.rutland@....com>,
        Chen-Yu Tsai <wens@...e.org>
Subject: Re: [PATCH v4 4/4] dt-bindings: net: broadcom-bluetooth: Add pcm config

On Thu, Nov 14, 2019 at 9:29 AM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Tue, Nov 12, 2019 at 3:10 PM Abhishek Pandit-Subedi
> <abhishekpandit@...omium.org> wrote:
> >
> > Add documentation for pcm parameters.
> >
> > Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> >
> > ---
> >
> > Changes in v4:
> > - Fix incorrect function name in hci_bcm
> >
> > Changes in v3:
> > - Change disallow baudrate setting to return -EBUSY if called before
> >   ready. bcm_proto is no longer modified and is back to being const.
> > - Changed btbcm_set_pcm_params to btbcm_set_pcm_int_params
> > - Changed brcm,sco-routing to brcm,bt-sco-routing
> >
> > Changes in v2:
> > - Use match data to disallow baudrate setting
> > - Parse pcm parameters by name instead of as a byte string
> > - Fix prefix for dt-bindings commit
> >
> >  .../devicetree/bindings/net/broadcom-bluetooth.txt    | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/net/broadcom-bluetooth.txt b/Documentation/devicetree/bindings/net/broadcom-bluetooth.txt
> > index c749dc297624..42fb2fa8143d 100644
> > --- a/Documentation/devicetree/bindings/net/broadcom-bluetooth.txt
> > +++ b/Documentation/devicetree/bindings/net/broadcom-bluetooth.txt
> > @@ -29,6 +29,11 @@ Optional properties:
> >     - "lpo": external low power 32.768 kHz clock
> >   - vbat-supply: phandle to regulator supply for VBAT
> >   - vddio-supply: phandle to regulator supply for VDDIO
> > + - brcm,bt-sco-routing: 0-3 (PCM, Transport, Codec, I2S)
> > + - brcm,pcm-interface-rate: 0-4 (128KBps, 256KBps, 512KBps, 1024KBps, 2048KBps)
> > + - brcm,pcm-frame-type: 0-1 (short, long)
> > + - brcm,pcm-sync-mode: 0-1 (slave, master)
> > + - brcm,pcm-clock-mode: 0-1 (slave, master)
>
> Since these are optional your patch should describe what happens if
> they are not present.  I think in patch #3 of the series you guys are
> discussing it, but whatever you end up with should be documented here.
>
Yes, I think I will document the default values here as well.

> That actually made me realize that this is patch #4 in the series.  To
> be pedantic, bindings are supposed to be _earlier_ in the series than
> the code that implements them.
>
>
> >  Example:
> > @@ -40,5 +45,11 @@ Example:
> >         bluetooth {
> >                 compatible = "brcm,bcm43438-bt";
> >                 max-speed = <921600>;
> > +
> > +               brcm,bt-sco-routing = [01];
> > +               brcm,pcm-interface-rate = [02];
> > +               brcm,pcm-frame-type = [00];
> > +               brcm,pcm-sync-mode = [01];
> > +               brcm,pcm-clock-mode = [01];
>
> I'm at least marginally curious why your example has a leading 0 for
> all numbers.  It makes me think you intend them to be represented in
> octal, though I don't know offhand if dtc uses that format for octal.
> I guess it doesn't matter since all your numbers are between 0 and 5,
> but it does seem strange.

It's a bytestring with a length of 1. See bytestrings under
https://devicetree-specification.readthedocs.io/en/latest/source-language.html#node-and-property-definitions

>
> -Doug