Re: Feature needed for EMU1820m driver

[James Courtier-Dutton <James@superbug.co.uk>]

Takashi Iwai wrote:
> At Wed, 27 Sep 2006 20:58:57 +0200 (CEST),
> Jaroslav Kysela wrote:
>   
>> On Wed, 27 Sep 2006, James Courtier-Dutton wrote:
>>
>>     
>>> Hi,
>>>
>>> The E-MU 1820m consists of a PCI card with a connector on it.
>>> A cable then runs to an external box called the AudioDock with all the
>>> audio IO on it.
>>> The AudioDock is hot pluggable.
>>> The problem is that no interrupts occur if one connects the AudioDock.
>>> One would have to poll the device until one saw a certain bit being set.
>>> One would then know the AudioDock was there. The driver then needs to
>>> load some firmware into the AudioDock.
>>>
>>> My question is, what should I use to monitor for the plug/unplug of the
>>> AudioDock? I would expect some user land app could do the polling, but
>>> that might require some new ALSA api to support it.
>>>       
>> I would use a low resolution (probably ~1 sec) system timer to check this 
>> bit and request the additional firmware in tasklet or workqueue. In this 
>> case, the userland is not required to participate.
>>     
>
> Agreed (tasklet cannot used for firmware loading, though).
>
> The unplug would be more tough, I guess.  The driver has to accept
> that the box can be unplugged at any time.
>
>
> Takashi
>   

Ok, that's and interesting problem them, because about the only thing it 
has to do when plugged in is load the firmware.

So, if a tasklet it not useable for firmware loading, what should I use?

It is a shame that the kernel does not have a global poll function, 
where one justs adds their function to a queue with minimum and maximum 
poll intervals, and a single kernel task then steps through each one 
doing the poll. If the poll returns true, the kernel should then 
schedule a function to be run. This would use less task switching.

James



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