netdev - Re: [PATCH v7 05/24] wfx: add main.c/main.h

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Date:   Fri, 01 Oct 2021 11:44:17 +0200
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 v7 05/24] wfx: add main.c/main.h

On Friday 1 October 2021 11:22:08 CEST Kalle Valo wrote:
> Jerome Pouiller <Jerome.Pouiller@...abs.com> writes:
> 
> > From: Jérôme Pouiller <jerome.pouiller@...abs.com>
> >
> > Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
> 
> [...]
> 
> > +/* The device needs 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.
> > + */
> > +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;
> > +}
> 
> I'm not really fond of having this kind of ASCII based parser in the
> kernel. Do you have an example compressed file somewhere?

An example of uncompressed configuration file can be found here[1]. Once
compressed with [2], you get:

    {a:{a:4,b:1},b:{a:{a:4,b:0,c:0,d:0,e:A},b:{a:4,b:0,c:0,d:0,e:B},c:{a:4,b:0,c:0,d:0,e:C},d:{a:4,b:0,c:0,d:0,e:D},e:{a:4,b:0,c:0,d:0,e:E},f:{a:4,b:0,c:0,d:0,e:F},g:{a:4,b:0,c:0,d:0,e:G},h:{a:4,b:0,c:0,d:0,e:H},i:{a:4,b:0,c:0,d:0,e:I},j:{a:4,b:0,c:0,d:0,e:J},k:{a:4,b:0,c:0,d:0,e:K},l:{a:4,b:0,c:0,d:1,e:L},m:{a:4,b:0,c:0,d:1,e:M}},c:{a:{a:4},b:{a:6},c:{a:6,c:0},d:{a:6},e:{a:6},f:{a:6}},e:{b:0,c:1},h:{e:0,a:50,b:0,d:0,c:[{a:1,b:[0,0,0,0,0,0]},{a:2,b:[0,0,0,0,0,0]},{a:[3,9],b:[0,0,0,0,0,0]},{a:A,b:[0,0,0,0,0,0]},{a:B,b:[0,0,0,0,0,0]},{a:[C,D],b:[0,0,0,0,0,0]},{a:E,b:[0,0,0,0,0,0]}]},j:{a:0,b:0}}


[1]: https://github.com/SiliconLabs/wfx-pds/blob/API4.1/BRD4001A_Rev_A01.pds.in
[2]: https://github.com/SiliconLabs/wfx-linux-tools/blob/SD4/pds_compress

> Does the device still work without these PDS files? I ask because my
> suggestion is to remove this part altogether and revisit after the
> initial driver is moved to drivers/net/wireless. A lot simpler to review
> complex features separately.

I think we will be able to communicate with the chip. However, the chip won't
have any antenna parameters. Thus, I think the RF won't work properly.


-- 
Jérôme Pouiller