Nouveau - Mar 2021 - How to reverse engineer a PCI-Express driver under Linux ?

Hello,

I?ve already asked this on the Kernel Newbies mail list, but as developing
nouveau seems to be kind of similar to what I want to achieve, I thought it
would be a good idea to ask it here as well.

I have a PCI-Express video capture card that has a proprietary driver for Linux.
I have some experience with programming in C, and so I would like to start a
hobby project to develop a free/libre driver for this device for Linux.
Of course I don?t have access to any documentation about how to communicate with
this device (I?ve tried to contact the company making these, but my hopes are
not high), so I think I will need to reverse-engineer the way the existing
driver communicates with the hardware. How could I achieve this ?

Also, the long term goal of this project would be to have this driver merged
into mainline, so what is allowed or not while doing this to avoid problematic
legal ramifications ?
Thank you for your help.

Best regards.
Tomek Lecocq

On Wed, Mar 3, 2021 at 11:07 AM Tomek LECOCQ <tomek.lecocq at hotmail.fr>
wrote:
> Hello,
>
> I?ve already asked this on the Kernel Newbies mail list, but as developing
> nouveau seems to be kind of similar to what I want to achieve, I thought it
> would be a good idea to ask it here as well.
>
> I have a PCI-Express video capture card that has a proprietary driver for
> Linux.
> I have some experience with programming in C, and so I would like to start
> a hobby project to develop a free/libre driver for this device for Linux.
> Of course I don?t have access to any documentation about how to
> communicate with this device (I?ve tried to contact the company making
> these, but my hopes are not high), so I think I will need to
> reverse-engineer the way the existing driver communicates with the
> hardware. How could I achieve this ?
>
>
Usually drivers map PCIe bars into the VM and read/write at certain offsets
to do.. stuff. In the linux kernel we have the mmiotrace tracer in order to
capture what a driver does with the hardware. You still need to interpret
the trace file, but at least this should give you the raw data on what's
going on. Hope that helps.

> Also, the long term goal of this project would be to have this driver
> merged into mainline, so what is allowed or not while doing this to avoid
> problematic legal ramifications ?
> Thank you for your help.
>
Best regards.
> Tomek Lecocq
> _______________________________________________
> Nouveau mailing list
> Nouveau at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/nouveau
>
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