Re: Tearing down DMA transfer setup after DMA client has finished

[Geert Uytterhoeven]

On Thu, Dec 8, 2016 at 12:44 PM, MÃns RullgÃrd <mans@xxxxxxxxx> wrote:
> Vinod Koul <vinod.koul@xxxxxxxxx> writes:
>> On Wed, Dec 07, 2016 at 04:45:58PM +0000, MÃns RullgÃrd wrote:
>>> Vinod Koul <vinod.koul@xxxxxxxxx> writes:
>>> > On Tue, Dec 06, 2016 at 01:14:20PM +0000, MÃns RullgÃrd wrote:
>>> >> That's not going to work very well.  Device drivers typically request
>>> >> dma channels in their probe functions or when the device is opened.
>>> >> This means that reserving one of the few channels there will inevitably
>>> >> make some other device fail to operate.
>>> >
>>> > No that doesnt make sense at all, you should get a channel only when you
>>> > want to use it and not in probe!
>>>
>>> Tell that to just about every single driver ever written.
>>
>> Not really, few do yes which is wrong but not _all_ do that.
>
> Every driver I ever looked at does.  Name one you consider "correct."

I'm far from claiming that drivers/tty/serial/sh-sci.c is perfect, but it does
request DMA channels at open time, not at probe time.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds