netdev - Re: [PATCH v3 05/24] wfx: add main.c/main.h

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Date:   Wed, 23 Dec 2020 13:09:01 +0100
From:   Jérôme Pouiller <jerome.pouiller@...abs.com>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "David S . Miller" <davem@...emloft.net>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        linux-mmc@...r.kernel.org,
        Pali Rohár <pali@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v3 05/24] wfx: add main.c/main.h

On Tuesday 22 December 2020 16:44:05 CET Kalle Valo wrote:
> Jerome Pouiller <Jerome.Pouiller@...abs.com> writes:
> 
> > +/* NOTE: wfx_send_pds() destroy buf */
> > +int wfx_send_pds(struct wfx_dev *wdev, u8 *buf, size_t len)
> > +{
> > +     int ret;
> > +     int start, brace_level, i;
> > +
> > +     start = 0;
> > +     brace_level = 0;
> > +     if (buf[0] != '{') {
> > + dev_err(wdev->dev, "valid PDS start with '{'. Did you forget to
> > compress it?\n");
> > +             return -EINVAL;
> > +     }
> > +     for (i = 1; i < len - 1; i++) {
> > +             if (buf[i] == '{')
> > +                     brace_level++;
> > +             if (buf[i] == '}')
> > +                     brace_level--;
> > +             if (buf[i] == '}' && !brace_level) {
> > +                     i++;
> > +                     if (i - start + 1 > WFX_PDS_MAX_SIZE)
> > +                             return -EFBIG;
> > +                     buf[start] = '{';
> > +                     buf[i] = 0;
> > +                     dev_dbg(wdev->dev, "send PDS '%s}'\n", buf + start);
> > +                     buf[i] = '}';
> > +                     ret = hif_configuration(wdev, buf + start,
> > +                                             i - start + 1);
> > +                     if (ret > 0) {
> > + dev_err(wdev->dev, "PDS bytes %d to %d: invalid data (unsupported
> > options?)\n",
> > +                                     start, i);
> > +                             return -EINVAL;
> > +                     }
> > +                     if (ret == -ETIMEDOUT) {
> > + dev_err(wdev->dev, "PDS bytes %d to %d: chip didn't reply (corrupted
> > file?)\n",
> > +                                     start, i);
> > +                             return ret;
> > +                     }
> > +                     if (ret) {
> > + dev_err(wdev->dev, "PDS bytes %d to %d: chip returned an unknown
> > error\n",
> > +                                     start, i);
> > +                             return -EIO;
> > +                     }
> > +                     buf[i] = ',';
> > +                     start = i;
> > +             }
> > +     }
> > +     return 0;
> > +}
> 
> What does this function do? Looks very strange.

I am going to add this comment:

The device need data about the antenna configuration. This information in
provided by PDS (Platform Data Set, this is the wording used in WF200
documentation) files. For hardware integrators, the full process to create
PDS files is described here:
  https://github.com/SiliconLabs/wfx-firmware/blob/master/PDS/README.md

So this function aims to send PDS to the device. However, the PDS file is
often bigger than Rx buffers of the chip, so it has to be sent in multiple
parts.

In add, the PDS data cannot be split anywhere. The PDS files contains tree
structures. Braces are used to enter/leave a level of the tree (in a JSON
fashion). PDS files can only been split between root nodes.

-- 
Jérôme Pouiller