Hi Archit,
On Tuesday 20 August 2013 18:46:38 Archit Taneja wrote:
> On Tuesday 20 August 2013 05:09 PM, Laurent Pinchart wrote:
>
> <snip>
>
> >>>> +static int vpdma_load_firmware(struct vpdma_data *vpdma)
> >>>> +{
> >>>> + int r;
> >>>> + struct device *dev = &vpdma->pdev->dev;
> >>>> +
> >>>> + r = request_firmware_nowait(THIS_MODULE, 1,
> >>>> + (const char *) VPDMA_FIRMWARE, dev, GFP_KERNEL, vpdma,
> >>>> + vpdma_firmware_cb);
> >>>
> >>> Is there a reason not to use the synchronous interface ? That would
> >>> simplify both this code and the callers, as they won't have to check
> >>> whether the firmware has been correctly loaded.
> >>
> >> I'm not clear what you mean by that, the firmware would be stored in the
> >> filesystem. If the driver is built-in, then the synchronous interface
> >> wouldn't work unless the firmware is appended to the kernel image. Am I
> >> missing something here? I'm not very aware of the firmware api.
> >
> > request_firmware() would just sleep (with a 30 seconds timeout if I'm not
> > mistaken) until userspace provides the firmware. As devices are probed
> > asynchronously (in kernel threads) the system will just boot normally, and
> > the request_firmware() call will return when the firmware is available.
>
> Sorry, I sent the previous mail bit too early.
>
> With request_firmware() and the driver built-in, I see that the kernel
> stalls for 10 seconds at the driver's probe, and the firware loading fails
> since we didn't enter userspace where the file is.
>
> The probing of devices asynchronously with kernel threads makes sense, so
> it's possible that I'm doing something wrong here. I'll give it a try again
I might have spoken too fast. It looks like module initcalls are not run in
threads. I've most probably mistaken that with asynchronous probing of hot-
pluggable devices.
If your driver is built-in then it looks like the correct solution is to build
the firmware in the kernel image as well, or use the asynchronous API as you
did.
--
Regards,
Laurent Pinchart
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