Re: [RFC PATCH] fpga: Introduce new fpga subsystem

Jason Gunthorpe
2013-09-23T17:10:47Z

On Mon, Sep 23, 2013 at 03:10:11PM +0200, Michal Simek wrote:

> > 1) The driver doesn't know what firmware to request. It just knows
> > how to send it to a FPGA.
>
> But dts property in the manager driver which uses this as end driver
> can know that.

I think the device tree maintainers would push back on this since it
is not "describing the hardware"

> > 2) Telling the kernel a filename via sysfs and then having it go
> > around the long way via request_firwmare to get the data is silly.
> > Just give the kernel the actual data instead of a file name
>
> Firmware interface is valid way how to pass bitstream to the kernel.
> If you don't like just don't use it. For example you can add
> firmware blob directly to the kernel and load this at bootup phase
> without user-space access.

I'm not against using request firmware for what it is ment for: having
the kernel autonomously load firmware.

I am against the sysfs API in the core code where userspace writes a
file name that is then used to request_firwmare. That is a goofy API
for the reasons I outlined.

It is appropriate to use request firmware at the driver level where
the driver somehow knows what FPGA to request.

> and there will be this option. But don't try to restrict others
> if they want to do it just in the kernel in early phase.

Doing the load in kernel early phase doesn't involve the user space
sysfs interface.

Jason