Message-ID: <87k0ixj5vn.fsf@codeaurora.org>
Date:   Fri, 01 Oct 2021 15:18:04 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Jérôme Pouiller <jerome.pouiller@...abs.com>
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

Jérôme Pouiller <jerome.pouiller@...abs.com> writes:

> 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}}

So what's the grand idea with this braces format? I'm not getting it.

Usually the drivers just consider this kind of firmware configuration
data as a binary blob and dump it to the firmware, without knowing what
the data contains. Can't you do the same?

>> 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.

RF not working properly is bad, so we can't drop PDS files for now. Too
bad, it would have been so much faster if we would not need to worry
about PDS files during review.

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

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