linux-kernel - Re: [PATCH v7 10/24] wfx: add fwio.c/fwio.h

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Message-ID: <87lf35ckn5.fsf@codeaurora.org>
Date:   Thu, 07 Oct 2021 11:19:10 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Jérôme Pouiller <jerome.pouiller@...abs.com>
Cc:     Pali Rohár <pali@...nel.org>,
        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, Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v7 10/24] wfx: add fwio.c/fwio.h

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

> On Friday 1 October 2021 18:08:32 CEST Pali Rohár wrote:
>> On Friday 01 October 2021 17:09:41 Jérôme Pouiller wrote:
>> > On Friday 1 October 2021 13:58:38 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>
>> > >
>> > > [...]
>> > >
>> > > > +static int get_firmware(struct wfx_dev *wdev, u32 keyset_chip,
>> > > > +                     const struct firmware **fw, int *file_offset)
>> > > > +{
>> > > > +     int keyset_file;
>> > > > +     char filename[256];
>> > > > +     const char *data;
>> > > > +     int ret;
>> > > > +
>> > > > +     snprintf(filename, sizeof(filename), "%s_%02X.sec",
>> > > > +              wdev->pdata.file_fw, keyset_chip);
>> > > > +     ret = firmware_request_nowarn(fw, filename, wdev->dev);
>> > > > +     if (ret) {
>> > > > +             dev_info(wdev->dev, "can't load %s, falling back to %s.sec\n",
>> > > > +                      filename, wdev->pdata.file_fw);
>> > > > +             snprintf(filename, sizeof(filename), "%s.sec",
>> > > > +                      wdev->pdata.file_fw);
>> > > > +             ret = request_firmware(fw, filename, wdev->dev);
>> > > > +             if (ret) {
>> > > > +                     dev_err(wdev->dev, "can't load %s\n", filename);
>> > > > +                     *fw = NULL;
>> > > > +                     return ret;
>> > > > +             }
>> > > > +     }
>> > >
>> > > How is this firmware file loading supposed to work? If I'm reading the
>> > > code right, the driver tries to load file "wfm_wf200_??.sec" but in
>> > > linux-firmware the file is silabs/wfm_wf200_C0.sec:
>> > >
>> > > https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/silabs
>> > >
>> > > That can't work automatically, unless I'm missing something of course.
>> >
>> > The firmware are signed. "C0" is the key used to sign this firmware. This
>> > key must match with the key burned into the chip. Fortunately, the driver
>> > is able to read the key accepted by the chip and automatically choose the
>> > right firmware.
>> >
>> > We could imagine to add a attribute in the DT to choose the firmware to
>> > load. However, it would be a pity to have to specify it manually whereas
>> > the driver is able to detect it automatically.
>> >
>> > Currently, the only possible key is C0. However, it exists some internal
>> > parts with other keys. In addition, it is theoretically possible to ask
>> > to Silabs to burn parts with a specific key in order to improve security
>> > of a product.
>> >
>> > Obviously, for now, this feature mainly exists for the Silabs firmware
>> > developers who have to work with other keys.
>> >
>> > > Also I would prefer to use directory name as the driver name wfx, but I
>> > > guess silabs is also doable.
>> >
>> > I have no opinion.
>> >
>> >
>> > > Also I'm not seeing the PDS files in linux-firmware. The idea is that
>> > > when user installs an upstream kernel and the linux-firmware everything
>> > > will work automatically, without any manual file installations.
>> >
>> > WF200 is just a chip. Someone has to design an antenna before to be able
>> > to use.
>> >
>> > However, we have evaluation boards that have antennas and corresponding
>> > PDS files[1]. Maybe linux-firmware should include the PDS for these boards
>> 
>> So chip vendor provides firmware and card vendor provides PDS files.
>
> Exactly.
>
>> In
>> my opinion all files should go into linux-firmware repository. If Silabs
>> has PDS files for its devel boards (which are basically cards) then I
>> think these files should go also into linux-firmware repository.
>> 
>> And based on some parameter, driver should load correct PDS file. Seems
>> like DT can be a place where to put something which indicates which PDS
>> file should be used.
>> 
>> But should be in DT directly name of PDS file? Or should be in DT just
>> additional compatible string with card vendor name and then in driver
>> itself should be mapping table from compatible string to filename? I do
>> not know what is better.
>
> The DT already accepts the attribute silabs,antenna-config-file (see
> patch #2).
>
> I think that linux-firmware repository will reject the pds files if
> no driver in the kernel directly point to it. Else how to detect
> orphans?

This (linux-firmware rejecting files) is news to me, do you have any
pointers?

> So, I think it is slightly better to use a mapping table.

Not following you here.

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