Re: [PATCH 1/6] v4l: ti-vpe: Create a vpdma helper library

[Archit Taneja <a0393947@ti.com>]

Hi Laurent,

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

Archit