Date:   Thu, 7 Oct 2021 12:10:03 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Kalle Valo <kvalo@...eaurora.org>
Cc:     Jérôme Pouiller <jerome.pouiller@...abs.com>,
        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

On Thursday 07 October 2021 11:19:10 Kalle Valo wrote:
> 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?

I understand this as, linux-firmware rejects files which are not used by
any driver yet.

But you can send both pull request for linux-firmware and pull request
for your kernel driver to mailing lists. And once driver changes are
merged into -net tree then pull request for linux-firmware can be merged
too.

> > So, I think it is slightly better to use a mapping table.
> 
> Not following you here.

I understand this part to have mapping table between DTS compatible
string and pds firmware name in driver code.

> -- 
> https://patchwork.kernel.org/project/linux-wireless/list/
> 
> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches

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