Re: trying out usb hotplugs

[Takashi Iwai <tiwai@suse.de>]

At Fri, 29 Nov 2002 15:05:21 +0100 (CET),
Jaroslav wrote:
> 
> On Fri, 29 Nov 2002, Takashi Iwai wrote:
> 
> > Hi,
> > 
> > the attached is my latest patch.
> > could you check it?
> 
> Let's go and make things more complicated (like in my tree on disc):
> 
> 1) waiting for time when all disconnected applications have closed
>    all file descriptors is a bit problem, because no new/other USB devices 
>    can be connected/disconnected; in my tree, I use thread to postpone 
>    freeing of snd_card_t structure

right.  i didn't touch this part at all.

another possible solution is to put the pending card instance into
a stale linked-list like in pcmcia drivers.
the pending objects are released at the time when a new device is
registered and when the module is removed.
but if a kernel-thread can work well, it's better, because it will
release the resources asap.

> 2) replace file->f_op with fake operations which allows only original 
>    release() callback in snd_card_disconnect(); this point makes things 
>    more and more simple than your code (check all accesses), because we 
>    need to count only open/release calls

yes, that's a better solution.

> 3) the unfinished problem is still: how to behave, if the disconnect event
>    comes in the middle of some code; you're right at this point, the 
>    lowlevel driver must handle it
> 
> Please, remove from your code any checks from ioctl(), poll(), read() / 
> write(). Then commit and I'll merge my tree with yours.

ok.


Takashi


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